LIBRARYOF THE

UNIVERSITY OF CALIFORNIA.Class

GEOLOGY FOB ENGINEERS.

Demy

8vo.

Handsome

Cloth.

STRATIGRAPHICAL GEOLOGY AND PALEONTOLOGY,ON THE BASIS OF PHILLIPS. BY ROBERT ETHERIDGE, F.R.S.,of the Natural Hist. Department, British Museum, late Palaeontologist to the Geological Survey of Great Britain, Past President of the Geological Society, etc.

With Map, Numerous"If Prof.

Tables,

and Thirty-sixits

Plates.

originality and the breadth of its views, Mr ETHERIDGE fully justifies the assertion made in his preface that his book Must take HIGH RANK differs in construction and detail from any known manual.

SEKLEY'S volume was remarkable for

.

.

.

AMONG WORKS OP REFERENCE."

A thenceum.

SIXTH EDITION, Thoroughly Revised.

With

Illustrations.

Cloth.

AIDS IN

PRACTICAL GEOLOGY:WITH A SECTION ON PALEONTOLOGY. BY PROFESSOR GRENVILLE COLE, M.R.I. A., GENERAL CONTENTS.I

F.G.S.

Part III. Examination of Rocks. Part I. Sampling of Earth's Crust. Part IV.- Examination of Fossils. Part II. Examination of Minerals. "That the work deserves its title, that it is full of AIDS.' and in the highest degree PRACTICAL,' will be the verdict of all who use it." Nature.|

'

'

With 12

Full-page Illustrations from Photographs. SECOND EDITION, Revised.

Cloth.

OPEN-AIR STUDIES IN GEOLOGY:AN INTRODUCTION TO GEOLOGY OUT-OF-DOORS. BY GRENVILLE A. J. COLE, F.G.S., M.R I.A.,Professor of Geology in the Royal College of Science for Ireland, and Examiner in the University of London. "The FASCINATING 'OPEN-AiR STUDIES' of Prof. COLE give the subject a GLOW OF ANIMATION cannot fail to arouse keen interest in geology." Geological Magazine. "A CHARMING BOOK, beautifully illustrated." A thenceum.. ..

In Crown 8vo.

Handsome

Cloth.

Fully Illustrated.

A HANDBOOK ON

THEODOLITE SURVEYING AND LEVELLING.FOR THE USE OF STUDENTS IN LAND AND MINE SURVEYING. BY PROFESSOR JAMES PARK, F.G.S.

"A

book which should prove as usefulNature.

to the

professional surveyor

as

to

the

student."

SECOND EDITION,

Revised.

Crown

8vo.

Handsome

Cloth.

Illustrated.

MINING GEOLOGY.Professor of Mining and Director of the Otago University School of Mines late Director Thames School of Mines, and Geological Surveyor and Mining Geologist to the Government of New Zealand.;

A TEXT-BOOK FOR MINING STUDENTS AND MINERS. BY PROFESSOR JAMES PARK, F.G.S., M.Inst.M.M.,

"A work which should find a place Mining World.

in the library of every

mining engineer."

LONDON

:

CHARLES GRIFFIN &

Co., LIMITED,

EXETER

ST.,

STRAND.

GEOLOGY FOR ENGINEERS

BY

LIEUT. -CoL.

R. F.

SORSBIE,

R.E.

mattb nearly 100 ^figures.

LONDON:CHARLES GRIFFIN & COMPANY, LIMITED,PHILADELPHIA:J. B.

L1PPINCOTT COMPANY.

7

PREFACE.IN these days of specialising in " watertight compartments," the bearing of geology in relation to almost every branch of engineer-

A knowledge of very frequently neglected or ignored. of the first importance to the practical geology is, however,ingis

engineer, but

it is difficult

for

him

to study the application of this

science to his requirements without having recourse to a large

number

of different textbooks

and other works.

References to

geology which are often of the greatest practical importance are often almost hidden away or treated in an obscure fashion, whereas the engineer requires the needful information to be

him

in a clear

and concise manner.

To meet

this

want

put before I have

endeavoured to compile the requisite information in one volume,in theI

hope that

it

may

serve as a

handy book

of reference.

greatly indebted to the various authors and publishers of the books mentioned in the accompanying list for so kindly allowing me to take such extracts as I required, and desire to record

am

my

grateful thanks to Professors Lapworth, Cole,

and Bauerman,

and Mr Hayden of the Geological Survey help and encouragement.

of India, for their kind

These extracts are referred to by a number at the end of each quotation corresponding with the number in the accompanyinglist.

R.

F.

SORSBIE.

January 1911.

226185

AUTHORITIES CONSULTED.1

Author.

Geology in Systematic Notes and Tables, by Wintour F. Allmann & Sons, 67 New Oxford Gwinnell, F.G S. ; 2nd edition. Street, 1889. 3 An Intermediate Textbook of Geology, by Charles Lapworth, F.R.S. William Blackwood & Sons, 1899.

2

Geology: Chemical, Physical, and Stratigraphical, vol. i., Chemical and Physical, by Joseph Prestwich. Clarendon Press, 1 886. 5 Geology : A Manual for Students in Advanced Classes and for General Readers, by Charles Bird, B.A. Lond., F.G.S. Longmans,

4

Green6

&

Co., 1894.

Manual of

Geology,

Theoretical

and

Practical,

by John

LL.D., F.R.S., Part I. Physical Geology and PalceonCharles Griffin & Co., 1885. tology, by H. G. Seeley, F.R.S. 7 Physical Geology, by A. H. Green, M.A., F.G.S. Longmans,Phillips,

& Co., 1898. filoxam's Chemistry (a few definitions only). 9 Physical Geology, by Ralph Tate, Weale's series. Lockwood & Son, 1907.Green8

Crosby,

The Standard English Dictionary (a few definitions). Economic Geology, by David Page, LL.D., F.G.S. Blackwood & Sons, 1874.11

10

Wm.

12 Textbook of Systematic Mineralogy, F.G.S. Longmans, Green & Co., 1903.13

by Hilary Bauerman,

Elementary Course of Geology, Mineralogy, and Physical Geography, by D. T. Ansted. John Van Voorst, 1856. 14 Textbook of Descriptive Mineralogy, by Hilary Bauerman, F.G.S. Longmans, Green & Co., 1902. 15 Aids in Practical Geology, by Grenville A. S. Cole, M.R.I. A., F.G.S. Charles Griffin & Co., 4th edition, 1902. 16 The Study of Rocks, by Frank Rutley, F.G.S. Longmans, Green & Co., 6th edition, 1894.

Vlll

GEOLOGY FOR ENGINEERS.

Vol. ii. of Prestwich's Geology (see No. 4). Historical Geology, by Ralph Tate, Weale's series. Crosby, Lockwood & Sons. 19 How to Observe: Geology, by H. T. de la Beche, F.R.S., etc. Charles Knight, 1835. !0 A Guide to Analysis in Geological and Agricultural Chemistry,18

17

by an21

Officer of the

First Book of William Collins & Sons.22

A

Bengal Engineers.Mineralogy,

by

J.

H.

Collins,

F.G.S.

The Principles of Waterworks Engineering, by J. H. T. Tudsbery, D.Sc., and A. W. Brightmore, D.Sc.; 3rd edition. E. & F. N. Spon, 1905. 23 The Water Supply of Cities and Towns, by W. Humber.Crosby, Lockwood & Sons, 1876. 24 Sanitary Engineering, by Vernon

Harcourt.

Green

Co., 1907'. 25 Treatise on Waterworks,

&

Longmans,

&

by

S.

Hughes.J.

Crosby, Lockwood

Sons, 1875.26

Quarrying and Blasting Rocks, by SirCrosby, Lockwood

Burgoyne, Weale's

series.

&

Sons, 1895.

27 Treatise on Building and Ornamental Stones of Great Britain and Foreign Countries, by Edward Hall. Macmillan & Co., 1872. 28 Charles Road-making and Maintenance, by T. Aitken. Griffin & Co., 1900. 29 Appendix by R. Mallet in Dobson's Brick and Tile Making, Weale's series. Crosby, Lockwood & Sons. 30 Calcareous Cements, by G. R. Redgrave and Charles Spackman. Charles Griffin & Co., 1905. 31 Limes, Cements, Mortars, etc., by G. R. Burnell, Weale's

series.32

Lockwood & Sons. 33 Road-making andGriffin

Crosby, Lockwood & Sons. Pioneer Engineering, by E. Dobson, Weale's

series.

Crosby,

Maintenance,

by

T.

Aitken.

Charles

&

Co., 1900.

34 The Construction of Roads, Paths, and Sea Defences, by Frank Latham, C.E. The Sanitary Publishing Company, Ltd.,

"Elementary Essay on Road-making," Art of Constructing Roads, by H. Law, C.E., Weale's series. Crosby, Lockwood & Sons. 36 An article on "Broken Stone Roads," by Reginald Ryves in Engineering, 1905, pp. 76 and 205. 37 The Rudiments of Civil Engineering, by H. Law, C.E., Weale's series. Crosby, Lockwood & Sons, 1882.quoted in Rudiments ofthe

1903. 35 Professor Mahon's

AUTHORITIES CONSULTED.S8

IX

Hydraulic Tables, by Nathaniel Beardmore.

Waterlow

&

Sons, 1852. 39 The General Principles of Mineralogy, by J. H. Collins, Wm. Collins & Sons. F.G.S. 40 Tidal Rivers, by W. H. Wheeler, M.I.C.E. Longmans, Green & Co., 1893. 41 Coast Erosion and Foreshore Protection, by J. S. Owens, M.D., A.M.I.C.E., F.R.G.S., and G. 0. Case. St Bride's Press, 1908. 42 An article on "Coast Erosion and Reclamation," in The

Engineer of 27th April 1906, and subsequent numbers.In addition to the above works from which extracts have been taken the following authorities have been consulted:

Geikie's Textbook of Geology.

" Geology Processes and their Results," Encyclopaedia Britannica. Chambers^ Encyclopaedia. Stevenson's Principles of Canal and River Engineering. Etc.

Class-book of Geology. Field Geology. Lyell's Elements of Geology. Murchison's Siluria. Dana's Manual of Geology. Penning's Field Geology. Marker's Petrology for Students. Hatch's Textbook of Petrology.:

Chamberlin and Salisbury

:

.

CONTENTS.INTRODUCTIONmaking, adopted:

Practical

Earthwork

Uses Water-supply, Building, RoadBranches of Geology Arrangement1_2

PARTINTRODUCTORY REMARKS

I.

DYNAMICAL AND STRUCTURAL GEOLOGY,3

CHAPTER I. CHANGES ON THE EARTH'S SURFACE.AGENCIES

DENUDATIONSectionI.

EFFECTS

SUB-HEADS

....Weathering,

4

The Work

of the Atmosphere.

(i)

Air.

(ii)

Changes of Temperature JEolian Action Transportive Action and Constructive Effects Loess, Sand-drift, Sand-dunes Rain Chemical A ction. Destructive ActionOxidation, Deoxidation, Carbonation, Hydration tive Effects Soil and Subsoil

Destructive

Action

4.7

Construc-

7_8

(iii)

Rain

Mechanical Action. Destructive Action Transport of Particles Earth Pillars Disintegration Constructive Effects Talus, Screes, Rain-wash

....... .

8-9

Section II.Source(i)

Underground Water.9-10Destructive Effects

AmountProcesses

Chemical Action.

Subterranean10-11

Channels, Caverns, and Swallow-holes(ii)

Constructive Effects.

Stalactites, Stalagmites, Petrifying Springs

Mechanical

Action.

Destructivexi

Effects

Landslips.

Con.

structive Effects

11-12

Xll

GEOLOGY FOR ENGINEERS.

Section III.Source(i)

Running Water.

Mechanical Action

Chemical Action

........; .

Erosion.(1)

Methods of Excavation Rate of Erosion depends on Nature of channel, (2) Rock formation, (3) Climate De-

(ii)

Transportation.

(iii)

velopment of Valleys Chemical Transporting Power Materials Composition Alluvium Occurrence of Deposits: (a) Alluvial Deposition. fans or cones (b) Alluvial plains (c) River terraces (d) Marine deltas (e) Lake deltas (/) Bars

.........;

;

;

;

Section IV.(i)(ii)

Glacial Agencies.Protective Action

Frost

and Snow. Destructive Action Formation Glaciers and Ice-sheets.

Movement

of Glaciers

Work of Glaciers Erosion Transportation and Deposition, Moraines, Perched blocks, Roches moutonne'esSection V.Gradation(i)

Marine Action.Breakers

Oceanic Movements.

Wave

-

action

Erosion(ii)

Transportation

Deposition

Under-tow Ocean CurrentsPelagic Deposits

Oceanic Deposits.

Terrigenous Deposits

Globigerina Ooze

Red Clay

Section VI.(i)

Organic Action.Constructive Action Constructive Action

Vegetable.

Destructive ActionDestructive Action

(ii)

Animal.

CHAPTER

II.

CHANGES WITHIN THE EARTH.Heat Hot Springs Pressure Water Internal Forces. Volcanic Products Lava, Rock - fragments, Bombs, Volcanoes. Decline of Volcanic Volcanic Vents Tuff Lapilli, Ash,Activity Mud Volcanoes Mud Springs Variation in the Sea-level Elevation and SubCrust Movements. sidence of Land Causes of Secular Movements

....Effects:

Cause Effects Earthquakes. Pressure Changes in Rocks. Cause Heat, Water,:

Trans-

formation,

Plication,

Consolidation

.........Metamorphism,Foliation,

Cleavage

CONTENTS.

Xlll

CHAPTER III. STRUCTURAL CHARACTERS OF ROCKS.INTRODUCTORY REMARKSSectionDefinitionI.

PAQB33

Igneous Rocks.

Extrusive and Intrusive

Contemporaneous or Extrusive Rocks.Subsequent or Intrusive Rocks. Laccolites BossesJoints.

Nature Cause Hexagonal Structure of Ice, Haematite, and quartz Columnar Structure of Basalt

........Sills

Lava Fragments Necks Veins and Dykes

...

33-34 3435

36-37

Section II.Changes(i)

Aqueous Rocks.37

after Deposition

Stratification.

Forms of BeddingStrata

Interposed

Laminae, Strata, False-bedding Character of Strata Alternation of

Beds(ii)

37-39

Inclination of Rocks.Inliers

Dip and Strike TJnconformability OverlapPlication

Outcrop

Outliers

and40-42

(iii)

Curvature or Flexure.clinal,

or Folds

Anticlinal,

Syn.

Monoclinal, etc

Nature, Sandstone, Clay, Limestone Master Joints Faults Throw Hade Reversed Faults (v) Dislocation. Step and Trough Faults Shift Fault-line Dyke Vein . .(iv) Joints.

42-43 43-44

44-45

Section III.Nature of Alteration

Altered and Metamorphic Rocks

Causes

...........

45-464647

Hydro-metamorphism. Action Results Thermo- or Contact Metamorphism. Action Effects Dynamo- or Regional Metamorphism. Cleavage Joints Foliation Relation between Igneous, Aqueous, and Metamorphic Rocks

47-50

PARTINTRODUCTORY REMARKS

II.

ROCKS AND MINERALS.51

CHAPTER IV. THE STUDY OF MINERALS.SOIL, ROCK,

AND MINERALS

52

XIV

GEOLOGY FOR ENGINEERS.SectionI.

Mineral Chemistry.CompoundEarthRadicle

PAQK

Definitions.

ElementSalt

Compound

AcidMetall oid

Base

Oxide

Terminations

Metal

Monad, Dyad, Triad, Tetrad, Organic Radicles Anhydride Elements Compounds Water Constituents of Earth. BeChemical Characters. Taste Odour Solubility in AcidsQuantivalence. .

.

.

.

52-54 54-5657

haviour (B.B.)

Section II.

Mineral Forms.Crystalline.

Mode of

Occurrence.

Amorphous

phous States Colloidal The Crystal Crystal Forms.SystemsModified Forms

Vitreous

.....Massive

Amor57-58

Crystallography

Axes

Crystal

Irregular Grouping of Crystals

Pseudomorphism

58-62

Cleavage. Structure.

Section III. Physical Characters. Laws of Cleavage Quality of Cleavage Columnar Lamellar Granular Imitative Shapes.. .

.

62-63

GlobularAcicularFracture.

ReniformStalactitic

Botryoidal

Mammillary

Filiform

DrusyConchoidal, Even, UnevenFriable

63-65

Form

of Surface

SurfaceTenacity.

Smooth, Splintery, Hackly, Earthy

....

Nature of65

Frangibility, Tough, Brittle, Soft,

Hardness.Touch.

Ductility Malleability Scale

Sectility . Rigidity, Flexible, Elastic

65-6666

Soapy

MeagreColour

Harsh

.

Specific Gravity.

Translucency

Definitions, Density, Specific gravity Kinds Intensity Streak Lustre.

.....

66 66 66-68

CHAPTER V. ROCK-FORMING MINERALS.Classification.

Native Elements

Sulphides

Fluorides

ChloridesSilicates

Anhydrous Oxides Hydrous SilicatesTitanateAbbreviations.

Hydrous OxidesCarbonates

Anhydrous

Sulphates

Phosphates69

HydrocarbonsApatite

Testing Minerals Andalusite Anhydrite List of Minerals.

69-70AragoniteCalcite

AsphaltCelestine

Epidote Felspars Garnet Glauconite Graphite GypGalena Fluor-spar Leucite Kaolin Iron Compounds sum Magnesite Manganese Compounds Micas and Talcs Nepheline Olivine Rock Salt Silica Series Sphene Sulphur TourmalineZeolites

Augite Hornblende group Copper Pyrites Dolomite

Barytes

Zinc-blende

70-93

CONTENTS.

XV

CHAPTER

VI.

THE STUDY OF ROCKS.DEFINITIONCLASSIFICATIONPAGE 94

SectionIgneous Rocks. Aqueous Rocks.AlteredPlutonic

I.

Mode

of Origin.

Volcanic

Hypabyssal

Arenaceous

and Metamorphic

Argillaceous Calcareous Hocks. Igneous Rocks Arenaceous.

.... ...

94-959595

Argillaceous

Calcareous

SectionGeneral Terms Igneous

II.

Chemical and Mineralogical Composition.96

Rocks.

Groups

Acid

Intermediate

Basic.

Ultra-basic

Chemical Constituents

Mineral Constituents

Aqueous Rocks. Arenaceous Argillaceous Calcareous Altered and Metamorphic Rocks. Principal Changes

... ....

.

96-9797

98

Section III.General Terms Igneous Rocks.Granitic

Structure.

98

Porphyritic

Felsitic

Matter

Columnar1.

Spheroidal

Drusy

Banded:

Structure.

Group

Dis-

tinctly Holocrystalline Rocks Pegmatitic or Graphic Gneissic Ophitic Orbicular. Group 2. Lithoidal

Fluidal

Rocks

1

:

Horny. Group 3. Glassy Rocks Perlitic Spherulitic Lithophyse Fluidal Pumiceous and Scoriaceous Amygdaloidal. Group 98-101 4. Volcanic Fragmental Rocks Agglomerate Brecciatad Aqueous Rocks. Group 5. Coarsely Fragmental Rocks Brecciated Stratified Rocks Conglomerate. Group 6. Ordinary Oolitic Pisolitic Laminated Pebbly Concretionary 101-102 Psammitic Altered and Metamorphic Rocks. Group 7. Rocks retaining tracesHemicrystallineMicrocrystalline:

Scoriaceous

:

.

:

:

Fluidal structure. Bedding Crystallisation Cleavage Foliation EyeGroup 8. Foliated or Schistose Rocks structure Granulitic. Mylonitic Group 9. Amorphous 102-103 Rocksof: :

Section IV.HardnessFracture

Physical Characters.StreakFeel

Colour and Lustre

and Smell

.

104-105

XVI

GEOLOGY FOR ENGINEERS.

CHAPTEREOCKS.INTRODUCTORY REMARKSSectionPlutonic Rocks.I,

VII.

PAGE 106

Igneous Rocks.PorphyryGranite Porphyry..

Granites

Syenites

Gabbro 106-109 109-111 Trachyte Andesites Basalt Rocks Volcanic Sands Volcanic Agglomerates Volcanic Fragmental Rocks. or Coarse Tuffs Tuffs and Ashes 111-112Quartz- Porphyry Volcanic Rocks. RhyoliteFelspar- PorphyryDiorite

Section

II.

Aqueous Eocks.

Fragmental or Clastic Rocks. (i) Arenaceous: Sand Sandstone Grit Conglomerate Greywacke Arkose BlueQuartzite Shale Mudstone Marl stone, 112-116 (ii) Argillaceous: Clay Rocks formed by Chemical or Organic Agencies. (i) Calcareous Limestone Dolomite Rock-Salt Gypsum, (ii) Siliceous Flint and Chert, Phosphatite Bone-beds (iii) Phosphatic Humus Peat Guano, (iv) Carbonaceous Coprolitic 116-122 (v) Ferruginous: Ironstones Lignite Coal,.

:

:

:

:

.

.

.

Section III.Classification

Altered and Metamorphic Eocks.122

Quartzite Lydian-stone Spotted Shale Purcellanite Slate 123-124 Serpentine. Crystalline Limestone Gneiss Mica Schist Classification Distinctly Foliated Rocks.

Altered Rocks.

.

.

Chlorite Schist

Talc Schist

Hornblende Schist

Calc Schist.

Mylonite

Granulite

Flaser gneiss

Augen

gneiss

,

124-128

Section IV.Igneous RocksSilicates

Eock Decomposition.

Felspars

Origin of Clays Decomposition of other Origin of Quartzose Sands and Sandstones Extent

Sedimentaryrocks

of Disintegration Strata. Alteration

128-132of.

Argillaceous

Freestones Colour Green Deoxidisation Bleached gravels 132-134.

CONTENTS.

XV11

PAKTINTRODUCTION

III.PAGE135

HISTORICAL GEOLOGY.

CHAPTER VIII. PRINCIPLES OF STRATIGRAPHY AND PALAEONTOLOGY.SectionFormations-TableI.

I.

Classification of Stratified Rocks.136-138 138-143 144-147 148-149150 151 152

Periods and Systems Sedimentary Strata in Great BritainClassified List of the Chief

.

.

.

.

Table

II.

AmericaTable III. Table IV.

........... .

Groups of Strata in North

List of the Formations in IndiaList of the

Sedimentary and Metamorphic Strata of.

AustraliaList of the Sedimentary Strata of New Zealand Table V. List of the Sedimentary Strata of South Africa Table VI.

.

SectionDefinitionsClassification of

II.

Palaeontology.

152-153 Spongida Coslenterata Echinodermata Annulosa or Vermes Arthropoda or Articulata Molluscoida 153-160 Mollusca Fishes Amphibia Reptilia Birds Mammals. 160-162 Vertebrata. 162 Classification of Plants 162 Phanerogams. Angiosperms GymnospermsInvertebrata.

Animals

......Thallophyta..

Protozoa

.

Cryptogams.

Pteridophyta

Bryophyta

.

162

CHAPTER IX. THE GEOLOGICAL SYSTEMS.CLASSIFICATION OF STRATA163

SectionIntroduction

I.

Anthropozoic or Quaternary Period.163

Recent or Post-glacial Formations.depositsPleistocene or Glacial Formations.

Human

Relics

Non-glacial

163-165Glacial Deposits

Continental EuropeAustralasia

North America

Great Britain Asia Africa

165-168II.

SectionIntroduction

Cainozoic or Tertiary Period.GreatBritain

Fossils

Continental

North America

Asia

Australasia

...

Europe.

168-171

XV111

GEOLOGY FOR ENGINEERS.Section III.

171 Great Britain Continental Europe North America South America Asia Africa Australasia 172-174 Great Britain Continental Europe Fossils Jurassic System. North America South America Asia Africa Australasia 174-175 Fossils Great Britain Triassic System. Continental TypesCretaceous SystemFossils.

Introduction

...........Mesozoic or Secondary Period.World-wide Distribution

PAGE

.

Europe

175-177

Section IV.Introduction

Palaeozoic Period177

Dyas

or

Great Britain Fossils Permian System. Continental Asia Africa Europe North America South America

Australasia

177-179Fossils

Continental Europe North America Asia Africa Australia 179-181 Fossils Great Britain Continental Europe Devonian SystemCarboniferous System.

Great Britain

.....

North AmericaSilurian System (Upper).Fossils

181-182Great BritainAustraliaFossils

Europe

North America

Asia

.....

Continental

182-184 184-185

Ordovician System (Lower Silurian).

Great Britain

Con-

North America Asia Australasia tinental Europe Cambrian System. Fossils Great Britain Continental Europe Asia North America Australasia

185-186

Section V.Britain

Eozoic Period.IntroductionFossils

Archaean and Pre-Cambrian Rocks.

Continental Europe Asia America Africa Australasia .

North America.

Great South.

186-188

PARTINTRODUCTORY REMARKS

IV.

GEOLOGICAL OBSERVATION.189

CHAPTERHammer

X.

OUTDOOR WORK.Equipment.Chisel

Bag and BeltAbney's Level

Walking-stickNote.

Compass book

Tape-measure

Pocket-leiis

190-191

CONTENTS.

XIX

SectionPreliminary Remarks

.........I.

Geological Surveying.

PAGE

Maps.

Contours

Tracing Boundary Lines..

191-192 192-194

Geological Sections

.

.

.

.

.

.

,

.

Section II.

Introductory Remarks Strata and their Inclination.Strike

.........Tracing Faults.

Structural Characters of Rocks.

195

Measurement

Dip and Principle of Stratification Curvatureof Thickness of Strata195-199. .

Overlap Unconformity Dislocation. Presence of a Fault

.199-200

Section III.Selection of Specimens.

Determination of Rocks.. . .

Rock-specimens. Structure Hardness Feeling SmellEffervescence Colour and Lustre Table VII. Easily Distinguishable Characters of RocksEasily distinguishable Characters..

Position

200

StreakFracture 200-202..

203-206

CHAPTER

XI.

INDOOR WORK.SectionI.

Further Examination of Rocks.

Hardness Specific Gravity Physical Characters. Detection of Carbonates Chemical Examination.Material

....

207-209

Summary

Preparation of of determinative Chemical Analysis of a

Rock

Fusibility

209-212

Section II.Mechanical Analysis.

Isolation of Constituents.

Crushing

Densetions

Liquids

Washing Magnetic Separation Use of Acids Determination of Propor213-218

Section III.

Determination of Minerals..

Mode

of Occurrence

Extraction

218

External

Form.

Preliminary

Examination

MeasuringHardnessSolubility

Crystal

AnglesPhysical Characters.

218-219Determina-

Determining Cleavage tion of Specific Gravity Fracture Chemical Characters. Taste and OdourSolvents

219-224Actionof.

224-226

XX

GEOLOGY FOR ENGINEERS.Section IV.

Blowpipe Examination..

PAGE

Apparatus and Reagents. Apparatus Reagents Use of Blowpipe 226-229 Blowpipe Operations. Assay Observation of Flame -col oration Observation of Fusibility First Operation (Closed Tube) Second Operation (Open Tube) Third Operation (Reactions on Charcoal) Fourth Operation (Cobalt) Fifth Operation (with Soda) Sixth Operation (Borax Bead) Seventh Operation (Microcosmic Salt) Eighth Operation Test for Sulphur 229-236 Table VIII. Colours of Beads 233-234.

PARTINTRODUCTORY REMARKS.

V.

PRACTICAL GEOLOGY.237

CHAPTERSectionRainfall. FallI.

XII.

WATER-SUPPLY.RainQuantity of Rain

Rainfall and Evaporation. Estimation of Mean AnnualFall

Maximum and Minimumand Absorption.

238-241

Evaporation

Effect

on

Evaporation from Surfaces of Water

Water-Supply Loss Dry Weather Flow

.

241-243

Section II.UndergroundWater.

Underground and Surface Waters.Water-slopeSaturation and

Imbibition.

Capacity of Rocks for Waterof Water

Surface

Waters.

Porosity of Rocks Surface of Saturation

Water-bearing Strata Yield Bournes Quality of Water 243-251Conditionsof

Flow251-253

Forests

Section III.

Springs and Wells.

Springs. Ordinary Springs Intermittent Springs Line of SaturaFault Springs Artesian Springs Springs as a Source tionof Supply

253-260Causes of Success or FailureQuality of Water.. .

Wells.

Shallow Wells Deep Wells Wells as a Source of Supply

260-262

Section IV.

Rivers.Strata

Flow of Water Quality of Water dependent on Schemes Flow of Streams and RiversTable IX.

River

Summer

Discharge of Rivers

263-266 266

CONTENTS.Section V.

XXI

Lakes and Impounding Reservoirs.Area

PA GE

Comparative Advantages Drainage Areas. Source of Supply Size of Catchment Available Rainfall Tendula ProjectLakes.

267

AdvantagesReservoirs. Sites

267-270 270. .

Impounding

Geological Features

.

271

CHAPTERINTRODUCTIONSectionGranitesI.

XIII.

BUILDING-STONES.272-273

Granites and Granitoid Rocks.Constituentsof

and

Syenites.

GranitesBritish

Qualities

Geological

Age

of Granite

Syenite

Granites and

Syenites

European GranitesGneiss

European SyenitesSerpentine

Table X.

Analyses Granitoid Hocks.Schists

273-279

PorphyryBasalt

Crystalline

Trap Hocks.

Greenstone

Lavas

Table XI. Analyses

.

279-281 281-287

Section II.

Sandstones, Limestones, and Argillaceous Rocks.. ..

Sandstones.

287-289 Weathering Properties of Sandstones and Limestones Old Lithological Character Cambrian and Silurian Red Sandstone Carboniferous Permian Triassic Jurassic Cretaceous Tertiary Table XII. Analyses of Sandstones 289-293.

Limestones.

Lithological Character

Marbles

ArchaeanJurassic

Silurian

DevonianTertiary

Carboniferous

Permian

Cretaceous

293-299Shales, and Clays). Silurian Devonian

Argillaceous Hocks (Slates, Characters CambrianSelection of Quarry

Lithological

Carboniferous...

Table XIII. Analyses

299-304

CHAPTERKaolin and FelspathicBritish ClaysFire-clays,

XIV.

BRICKS AND CLAYS.Clays.

Mud Loam,Qualities

Colouringetc.

Fire-bricks,

Floating BricksScience of Brick -making.

Fire-clays Terra-cottas

Shales, Marls, etc. Brick and Tile Clays 305-309 Dinas Bricks Firestones.

309-311

NormalColours

Choice of Clay Clays Foreign Bodies Constituents Laws of Induration Contraction

Table XIV. Analyses

.

.

.

.

.

.

311-317

XX11

GEOLOGY FOR ENGINEERS.

CHAPTERLIMES, CEMENTS,

XV.

AND PLASTERS.PAGE. .

DEFINITION OF CEMENTS AND LIMES INTERMEDIATE LIMES 318-319 Combination of Lime with Water Quicklime Slaked Lime Limes. Lime slowly recombines with Carbonic Acid Classification of Limes 319-321 The Influence of Clayey Matters Artificial Hydraulic Limes. Admixture of Clayey Matters Pozzuolana, Trass, etc. Influence of Heat on the Silicates 321-322

...........

Limestones.

Subdivisions

Chemical Nature of Stones furnishing.

different Sorts of

Calcination.

Lime Kilns and Fuel

.

322-323Results of

Admixture with AshesBerthier's

CalcinationTesting Limes

323-324

and Limestones.

Mode

of Analysis.

The.

Treatment with Muriatic Acid Influence of Calcination Roman Cement Energy Portland, Selenitic, and Magnesium Cements of America Sesvage Sludge Cements Plasters. Plaster of Paris Keene's and Parian Cements General Laws Probable Position of Different Geological Distribution. Materials Lias Lime British Limestones . .Condition of the SilicaCements...

325-326

326-328 328-329329-332

.

.

CHAPTER

XVI.

ROADS AND CANALS.SectionI.

Road-making.KnowledgeDetermination

Selection of Route. Value of Geological of Route Laying out Roads

New

333-334

Road

Construction.

Road-cuttings

Side-slopes

Methods of Drain334-338

ageSubsoil DrainageMountain Roads.DescentCrossing Watersheds.. .

Mountain Passes. .

.

....

Line of.

338-341

Section II.

Road

Materials.

. . Classes of Roads Water Influence of Weather. " Materials for Wearing" Roads. Local Circumstances

.341-343343-344 345-346 346-347 347-348

Suitable

Road MetalLimestone Gravel Materials for Weather-resisting Roads. Binding Material. Choice On Main Roads On By-roads. . .

.

Paving Materials.

Asphalt

Selection of Materials. Durability of

Tar-macadam Requisites in a Road Stone Physical Tests Road Stones Coefficients of Quality 348-351. .

CONTENTS.Section III.Level Surface General

xxiii

Canal-making.Leakage-

PAQE

Natural Feeder

Strata passed through

Remedy

351-353

CHAPTER

XVII.

RIVERS.Motion of Water in Rivers. Motion of Water Retarding Force Velocity Contour Rotary Motion of Particles Dynamic Action 354-358 The Transporting Power of Water. Transport of Material Erosion Quantity of Material Motion of Particles of Matter in Suspension Effect of Alteration in Dimensions of Channel 358-362 Proportion of Deposit carried Material transported The Physical Condition of Tidal Rivers. Origin and Description of Rivers Agents of Maintenance Regime of Rivers Junction of Rivers with the Sea Source of Detritus in Rivers Effect of obstructing the Free Flow of the Tide 362-365 Bars at the Mouth of Rivers. Description Bars composed of Hard Material not affected by the Scour of the Current Bars due to the Deposit of Alluvial Matter Bars at the Mouths of Sandy Estuaries Formation of Sandbars Channels where Bars are absent Theories as to the Cause of Bars 365-368 River Improvement Schemes. 368 Geological Formation of River Bed Land Reclamation. Embanking and Warping 368-369..

......

.

....

.

CHAPTERINTRODUCTORY REMARKSSectionOutlineI.

XVIII.

COAST EROSION.370

Coast-lines

and their

Origin.Inlets

Influence of Altitude

Minor Features

Headlands

The ShoreSectionWaves.FreeII.

Sea-cliffs

370-373

Forces acting on Coast and Sea-bed.Wavesof Translation

Waves

Forced Waves

Close

Overtaking of One Wave by Another Direction of Waves Oblique Waves 373-378 Tidal Action. Slow Rise and Fall Tidal Currents . . 379-380 Joint Action of Waves and Currents. Movement of Material 380 . Wind-formed Currents. Effect of Wind Undercurrents Alongshore Currents . 380-381.

to the Breaker Line

Breakers

Percolation

.

.

.

XXIV

GEOLOGY FOR ENGINEERS.Section III.

Coast Erosion and Eeclamation.

PAQE

Subsidence and Upheaval of the Physical Causes of Denudation. Earth's Crust Physical Causes of Sea Encroachment RiverDetritusProtective Works.

Effect of Deposits

of Littoral Drift to

on the Deep-sea Bed Relation 381-384 Eroded Material Deep-sea Erosion.

.

Impossibility of Entire Prevention of Erosion Effect of Protective Works on Adjoining Coast-line National Aid in Coast Protection Effect of Pier Works and other

Artificial Projections Littoral Drift. Effects of Coast Contour Effects of Tide and Wind

384-387

and River Estuaries

Sea Watts and Groynes.

Se* Walls

Groynes

....

387-388 388-390

CHAPTER

XIX.

USES OF MINERALS.Distribution of Valuable Minerals and Rocks. Coal Silver Platinum Mercury Tin Copper

....Iron

Gold

391-393393-394

Other Useful Minerals.

Barytes

Anhydrite

Gypsum

Asbestos

Mica Mineral Pigments.Ultramarine

Reddle Umber Metallic Pigments Table

Ochre

Bole

....Whiting.

394-396

INDEX

397-423

LIST OF ILLUSTRATIONS.PIG.1.

PAGEMillstone grit, Yorkshire6

6

2.3.

Rocks passing up into

soil 1919.

8

4. 5.6.

Section of ossiferous cavern with stalactites and stalagmites Fan at Tigar in Nubra at Ladakh 6

11

16

The Mer de Glace 6 Diagram of crag andVolcanic dykes19

tail

419

.192119

18

7.8. 9.

Action of the sea on the rocks of the coast

Columnar structure9

of basalt

.......6

353737

10. Jointed structure of granite11. False-bedding12.

19

38

Lenticular, interposed, and divided beds 6 13. Exchange or alternation of beds14. Section of outlier15. 16. 17.18.6.-

.3940 40 40

39

.

Map

of outlier6

6

Mapofinlier

....

Section of inlier

6

40

Unconformity of stratification 19. Diagram of overlap 620. Anticlinal dip66

.........6

4141

42 429

21. Synclinal dip 22. Breadth and throw of a fault23.

4444

Dislocation of strata6

6

24. Dislocation of vein 25.26.

45456. .

Reversed fault

6

27.28. 29.

Showing that cleavage does not pass through a bed of sandstone 6 Parallel cleavage in contorted strata of North Devon.

48 48

.

Ideal section

6.

Cubic system 13 30. Tetragonal system31.

.

.

.

39

50 59 60606161

Rhombic systemOblique system

13

32. 33.

*>

1313

Doubly oblique system

........

XXVIF *G 34.-

GEOLOGY FOR ENGINEERS.13

Hexagonal system

...........

PAGE61

35. Imitative shapes 36. Nummulites 6

64 153

37.

Monograptus (MurcMson)17

154 154

38. Diplograptus 17 39. Didymograptus 40. Rastrites (Lyell) 41. Lithostrotion 3 42. Calceola3

154. ..

.154154 154155

43.44.

Madrepora

3.

Favosites ( Murchison)

.

.

.

.

.

.

.

.155155 155

45. Heliolites

46. Syringopora 47. Pentacrinus48.

(Dana) (Dana)63.

155. ..

Encrinus

liliiformis

.'

.

.

.

49. Cypris 15 50. Estheria

.,

.

.

.

.155 .156156

3 17

51. Eurypterus 3 52. Olenellus

...''.

.

..'..'."

.

53. Paradoxides (Murchison) 15 54. Fenestella 55. Spirifer 56. Rhynchonella57.15"

.

.156 .157 .157.

15. .

.

Productus3

15.

.

58. Terebratula

6.

..........'

^.'

.

..

.

,.

.

.

.

157 157 158158 158

'

.

.

.

.

.

.

.158

59. 60.61.

62.

63.

Gryphsea 3 . Cyrena 3 Hippurites Gasteropods (a) Bellerophon 3 (d) Paludina Nautilus 6

....

.

.

.

^

.

.

.158158;

:

;

(b)

Limnaea

;

(c)

Planorbis (Lyell)

64. Goniatites (Lyell)65.

.

.

.

.

v

. .

'...,..159..

159 159

.

..

Ceratites

3..

.

.

.

.

,

.159159.

66.

Ammonites3

6

67. Turrilites68. Scaphites

3 3.

69. Orthoceras

70. Belemnites71. 72.

15

....ls 9

.

v

.

.,.

...".. ... .....

'

.

.

159 159

.

.

.

160160

.

.

.160\197 198

Hamites (Geikie) Measurement of dip

73. Calculating thickness of strata 74. Thoulet's 75. 76. 77.78.

washing apparatus

15

.

........214,..

.

.

.

Hollow collecting water ^ Spring arising from water falling on outcrop

Spring at outcrop of permeable stratum

w

23

Syphon

action

23

254 254 254 255

LIST OP ILLUSTRATIONS.FIG.

XXV11

79.

at outcrop of permeable between * 80. Inclined line of saturation

Water

81. Inclined line of saturation82. Origin of

two kinds of springs

83. Spring in valley caused84.85.

86.

by fault ^ Spring on hill caused by fault thrown out by a dyke w Spring Water held down in porous bed by superimposed imperviousstratum 23 Natural fissure givingrise to artesian

87.88.

Surface of saturation near a river

89. 90.

Road-cuttings in mountain pass

Road-cutting in mountain pass 91. Oscillation of particles of water92.

Action of oblique waves 41 41 . 93. Erosion by parallel waves 94. Joint action of waves and currents

....... ....... ..... ...... ....... ....... .......... ...... ...... ....... ........ ...... ......two impermeable beds.

*

256 256257

25

*

.

.

25

257 258 258

259 259

^.

spring

w

32

259 263 340341

^41

.

.

.

.

.

.

41

374 378 379 380

GEOLOGY FOR ENGINEERS.INTRODUCTION.the science which investigates the history of the nature and formation of the rocks which form the solid framework of the globe ; of the agents which produce changes in these rocks ; and of the history of the past 2 life, whose remains (fossils) are buried in them. Practical Uses. The advantages to engineers of a knowledgeis

GEOLOGY

earth.

It treats of the

and

be palpable to all who study their profession, employed abroad, who often must win from Nature the materials with which they may eventually defy her destructive efforts. The following are some of the practicalof this science will

especially to those

l uses of a knowledge of geology It explains the natural drainage of a district, etc. Water-supply, both surface and subterranean ; and it shows where artesian wells are possible, as also where fissures and faults exist. It affords indispensable information as to (1) the Building. composition of various rocks fit for particular uses, e.g. for:

building -stone, for bricks, for mortar and cement, for tiles and the way in which the rock has been affected by the weather, where exposed in cliffs and quarries, affords a valuable guide as to its durability ; (2) the areas covered by rocks yielding these materials, and their relative position among other strata, and how best worked. Road-making. It is of great importance in guiding the engineer (1) as to the choice of a line of road, so as to ensure its proper drainage, and prevent slipping: this will depend on the nature and succession of the strata and their dip ; (2) as to roadmetal what rocks are obtainable, what rocks are preferable, and what rocks are unsuitable. Earthwork. To the engineer making tunnels, cuttings, andslates: :

1

,

^ -3

HJg g0} of a comb. heterocercal (with unequal lobes), or homocercal (with symmetrical3

lobes).

The vertebral column is straight throughout, and its terminal portion is symmetrically surrounded by the caudal fin. In the others this terminal portion is bent obliquely upwards, and the lower part of the caudal fin is, 3 developed into a distinct lobe, so that the tail becomes bilobed in form.-

*

SECT.

II.]

PRINCIPLES OP STRATIGRAPHY AND PALAEONTOLOGY.

161

Groups of Fishes. (1) Teleostei (perfect-boned), with the whole of the internal skeleton osseous and the tail homocercal ; e.g. most

modern(2)

fishes.;

Ganoidei

ganoid

and heterocercal

tails, e.g.

scales, osseous or cartilaginous skeleton, Palgeozoic fishes.

(3) Elasmobranchii (plate-gilled) include sharks and rays, skin unprotected or with scattered, isolated scales, cartilaginous skeleton ; e.g. Hybodus, Acrodus. (4) Dipnoi (double breathers) include mud-fishes ; e.g. Ceratodus. (5) Marsipobranchii (pouch-gilled) include the Ostracodermi or

shell-skinned, Cephalaspis

and Pteraspis.

These have the character of fishes in the young or Besides the tadpole stage, and of reptiles in their adult state. Batrachians, frog, toad, etc., and the recent tailed forms, newt, etc., there were Labyrinthodonts, bone-clad forms with peculiar teeth, and often of colossal size, Mastodonsaurus, found only in 2 Carboniferous, Permian, and Triassic rocks. can be distinguished from Amphibians by the articulaReptilia

Amphibia.

tion of the skull to the vertebrse, the complexity of the lower jaw, and by the teeth having one fang. 5 Of the ten orders known only four still live:

and turtles, dating from Jurassic times. Snakes and serpents, unknown before Tertiary times. (3) Lizards, including the Permian Proterosaurus (the earliest known reptile), the Triassic Telerpeton, and the gigantic Cretaceous Mosasaurus.(1) Tortoises(2)

(4) Crocodiles, including the Stagonolepis of the Trias, Teleosaurus of the Oolite, and Goniopholis of the Cretaceous.

The

(5) Ichthyosauria,

chief extinct orders, all Mesozoic only, are from the Trias to Chalk.

:

(6) Plesiosauria, Trias to Chalk. (7) Ornithosauria or Pterosauria, flying reptiles, Pterodactylus,etc.,

from the Lias to Chalk.;

Dinosauria, huge reptiles Atlantosaurus (100 feet long). 2(8)

Iguanodon,

Megalosaurus,

The earliest known form is Archceopteryx of the Upper with a long bony tail, toothed and very like a reptile. Bird fossils are never abundant, but are fairly common in Tertiary strata. 2 Mammals. (1) Marsupials; having pouches for carrying the young. (2) Cetaceans ; whales, porpoises, dolphins.Birds.Oolites,

(3) Sirenians (4)

; manatee, etc. Edentates (toothless) ; armadillo, Glyptodon, Megatherium.;

(5) Insectivores(6) Bats.

mole, Stereognathus.

u

162(7)

GEOLOGY FOR ENGINEERS.Rodents;

[PT.

III.

CH.

VIII.

beaver, hare, mouse, etc.tapir, Palceo-

(8) Ungulates, including horse, pig, rhinoceros, therium ; also the Ruminants, ox, elk, deer, etc. ;

and Probosci-

deans, elephant, Mastodon, Dinotherium. (9) Carnivores ; lion, cat, dog, bear, hyaena.(10) Primates ; monkeys, apes, and man. Plants have been arranged by Classification of Plants. botanists into two main divisions or sub-kingdoms namely, the Phanerogams or flowering plants; and the Cryptogams or non32

flowering plants.order.

The

following arrangement

is

in

descending

PHANEROGAMS.Angiosperms. True flowering plants, often bearing bright bells or brilliant clusters of bloom, and always having their seeds enclosed in some more or less conspicuous form of enveloping fruit.Plants with two cotyledons or seedDicotylce or Dicotyledons. also called Exogens from their mode of growth outwards lobes forming annual rings of growth, as in all our shrubs and forest trees.in Tertiary strata. Plants with one seed-lobe, inMonocotyledons or Endogens. Ex., grasses, palms, lilies, creasing by additions in the interior. arums. They date from Carboniferous age. Gymnosperms. Plants with naked seeds, i.e. not contained in a seed-vessel; mode of growth exogenous, like that of the dicotyledons. Cycads, palm-like plants with hard leaves, easily preserved. They date from Permian times. Firs, pines, yews, etc., with resinous wood (the fibres Conifers.of

They date from Upper Cretaceous and abound

which have peculiar markings) and usually cone-shaped These date from Devonian.CRYPTOGAMS.

fruits.

Pteridophyta or Fern-plants. Lycopods or Club-mosses, the most abundant of Carboniferous plants. Equisetites or Horse-tails,with pointed stems.

abundant and

Ex., Calamites, Equisetum. Ferns, often of tree-like size, from Devonian or Silurian times.1

Ex., Cyclopteris, Neuropteris, etc. Bryophyta or Moss-plants.

Mosses

form

beds

of

peat

;

Sphagnum, the bog-moss Thallophyta. FungiAlgce

;

Liverworts. 1

Mushrooms,

lichens, etc.

rare as fossils.

Sea-weeds, etc., occur fossil from Cambrian period. Some, which secrete mineral matter, form rock-deposits, e.g. Corallines and Nullipores, with calcareous incrustation ; Diatoms, with beautiful siliceous cases, and Chara, with encrusted stems and fruits, 1

SECT.

I.]

CHAPTER

IX.

THE GEOLOGICAL SYSTEMS.Classification of Strata.If classed as to their place

and mode

of formation strata are terrestrial, lacustrine, fluviatile, or marine. Terrestrial deposits on old land surfaces are marked by tree-

stumps

in position as they grew, with tree-stems, leaves, fruits, land-shells, insects, etc., in the old soil round their roots. Lacustrine deposits in old lake beds and Fluviatile deposits in old

river beds are(a)

marked by

:

of shell-marl or limestone, full of fresh-water shells. shells or insects, leaves, fruits, etc. (b) Clay containing these Iron-stained sand, gravel, and conglomerate with fresh(c)fishes, etc.2

Beds

water and land plants,sea-shells,

Marine deposits on old sea bottoms are marked by sea-weeds,echinoderms, corals, foraminifera,I.

etc.

Section

Anthropozoic or Quaternary Period.all

that time which elapsed between the and the present day. There is no break either stratigraphical or palseontological between the Tertiary and the Quaternary, but the latter is signalised by the It is not possible to commencement of the Glacial epoch. arrange the Quaternary accumulations in strict chronological order, because their relative antiquity is so often indeterminable. In the glaciated regions of the northern hemisphere the various Glacial deposits are grouped as the older division under the name of Pleistocene, and the younger accumulations which lie above them are named Recent or Post-Glacial. 8

This period includes

close of the Tertiary period

RECENT OR POST-GLACIAL FORMATIONS.

Human Relics. In most of the non-glacial deposits we find evidence of the existence of man, in the form of implements of stone, bone, etc., and the study of this special branch of geology163

164

GEOLOGY FOR ENGINEERS.

[PT.

III.

CH. IX.

shades insensibly into the science of archaeology. 1 The following is the chronological classification of the deposits yielding traces of

human workmanship whichlogistsTT:.

is

generally employed by archaeoof

('

(

(

Prehistoric

3 Pecopteris, Glossopteris, Cycads and Conifers. Great Britain. There are two sections the Lias and the the former consisting typically of dark shales alternating Oolite with thin beds of blue or grey limestone, and the latter of alternations of massive calcareous rocks with thick sheets of softpods, Terebratula(fig.

58),

3 grey clays and marls.

The Liassic strata stretch across England in a narrow strip, varying from 1 to 20 miles wide, from Lyme Regis to Whitby and the mouth of the Tees. The Oolitic strata form a wider tract directly to the east of the Lias. 5 The Lias is marine throughout, but affords beds of iron-ore in Yorkshire (Cleveland) ; the Lower Oolites are marine and estuarine towards the north ; while the Middle Oolites are invariably The Upper Oolite is best developed at Swanage and marine. Portland, and shows fresh-water beds in its upper zones (Purbeck). Outliers of the Lias occur in England at Needwood, Whitchurch, and Carlisle in Ireland in the county of Antrim, and also in ScotIn Skye and Ramsay the Lias is 1200 feet thick, and is land. At followed by the Inferior Oolite, Great Oolite, and Oxfordian. Brora estuarine beds of Jurassic age have been worked for coal. 3 Continental Europe. The formations of the English Jurassic are continued into France and Germany, and are well displayed round the Paris basin, in the Franco-Swabian area, and N.W. Germany. In these areas the same divisions and fossil zones are recognisable as those in England, but the nomenclature is that of;

SECT.

III.]

THE GEOLOGICAL SYSTEMS.

175

In the Jura and in Provence the strata are rich in but are greatly folded. The Jurassic formations extend along the whole course of the Alps, but vary in thickness and lithological members, the Upper Oolite being the most widely The Russian type of the Jurassic covers much of Russia extended. and Siberia, and forms a broken zone round the (north) polar

D'Orbigny.

limestones,

regions.

In Swabia petroleum occurs in the Upper Lias marls ; Products. seams of coal of the Yorkshire Jurassic type occur in Bohemia and in Hungary. Lithographic slabs are procured from the limestones of Solenhofen in Germany. 3 North America. In the United States Jurassic rocks cover broad areas in Nevada, Dakota, Utah, and Colorado. In the western districts, especially in Colorado, they have afforded a remarkable series of reptilian forms. 3 South America. Jurassic beds occur in the Andes of Chili and Peru. 17 In India a thick development of Oolite rocks more than Asia. 6000 feet thick occurs in Cutch. The upper divisions (Rajmahal,etc.) of

the great fresh- water

Gondwana

series of Central India are

3 also of Jurassic age. Upper Jurassic strata are also represented in Punjab and the Himalayas. 17

consists of

of South Africa, which saliferous strata, sandstones, limestones, shales, and 17 conglomerates, represents the whole of the Jurassic series.

Africa.

The Uitenhage formation

land,

The Burrum Coal Measure formations of QueensAustralasia. 3 the Wainamatta series of argillaceous shales and thick sandstones of New South Wales, and the Carbonaceous formation of Victoria, which is 5000 feet thick, are of Jurassic age. 17 A massive series of marine and fresh-water beds with coals occurs in New Zealand. 3TRIASSIC SYSTEM.

Types.facies:

(1)

There are three fairly distinct types or paleeontological the Marine type of the Alps ; (2) the Mixed or semi-

marine, semi-continental type of the German Trias; (3) the inland or continental type of Great Britain, South Africa, and Eastern North America. 3Fossils.

The advent of Mammals and Ammonites.

Vertebrata.

Fishes Elasmobranchs, Hybodus, Acrodus ; Ganoids, Palceoniscus ; andDipnoids, Ceratodus. Of Amphibia LabyrinthoOf Reptiles Lizards, donts, Mastodonsaurus, Trematosaurus.Ichthyosaurus, Notosaurus, Telerpeton, Rhyncosaurus ; creatures with crushing teeth, Placodus ; Crocodiles, Stagonolepis. Of Anomodonts (in S. Africa) the mammalian-toothed Galeosaurust

Of

176theequal-toothed

GEOLOGY FOR ENGINEERS.Pariasaurus,etc.

[PT.

III.

CH. IX.

Dicynodon (rordonia,Microlestes.

and the double dog-toothed Of Mammals the teeth and jaws of

Nautilus

Cephalopoda are abundant, Ceratites (fig. 65), 63), Orthoceras (fig. 69), and a few Ammonites. Crinoids are also abundant, Encrinus liliiformis (fig. 48). LamelliInvertebrata.(fig.

branchiatacontorta.

are numerous, Myophoria, Gervillia, and Avicula Gasteropoda occur. Of Crustacea, Estheria (fig. 50),

and Brachiopods, Terebratula, are representative. Flora. Pecopteris, Equisetum, Conifers and Cycads. Great Britain. The Triassic system is most fully developed in the central parts of South Britain, and varies from 750 to 5000 feet in thickness. The Lower Trias or Bunter is formed of the Upper and Lower Variegated Sandstones, with the intermediate Pebblebeds and the Upper Trias or Keuper is made up of the Keuper marls and waterstones. The Bunter series is almost barren of fossils, except in its intermediate zones, where the derived pebbles;

The Keuper is equally contain a few fossils of pre-Triassic age. barren in organic remains. Triassic strata occur also in the basins of the Sol way, the Moray Firth, upon the western coasts and islands of Scotland, and in some of the counties of North-East " Ireland. The Rhsetic or " passage beds occur as a thin band from north of Yorkshire to the Dorset coast. 2 Continental Europe. Triassic rocks occupy the greater part of Germany the Bunter locally affords beds of dolomite, and sandThe distinct central member, the stones with plant remains. Muschelkalk, which is absent in Britain, is generally rich in fossils, while the lower half of the Keuper is marked by impure coal and the upper half by its abundant gypsum beds. The marine development of the Trias is typified by the thickbedded limestones, dolomites, and calcareous shales of the Eastern The individual beds Alps, rich in invertebrata of all types. cannot be paralleled with the German formations, but on the whole are their equivalents in time. 3 World-wide Distribution. The marine strata of the pelagic or Alpine facies of the Trias are of almost world-wide distribution they occur in the Maritime Alps, Apennines, Spain, Balkan Peninsula, Turkestan, Himalayas, and practically surround the Pacific Ocean, being met with in Peru, Colombia, Nevada,;:

California, British Columbia, Alaska, Japan, New Caledonia, and Zealand ; they also occur in Siberia and Spitzbergen. In all these regions their limestones yield the Ammonoid forms Ceratites,

New

Trachyceras, and the Lamellibranchs Daonella, etc. Triassic beds of the continental type occur in South Africa (Karoo series), where they yield the rich reptilian fauna already

SECT. IV.]

THE GEOLOGICAL SYSTEMS.

177

described.

They occur also in South India (Panchet beds), where they yield a few of the same forms. In the coastal regions of North-East America the Trias is represented by red sandstones and shales with abundant footprints of Dinosaurs (Connecticut), with local sheets of melaphyre (Palisades, etc.) and with plantremains (Virginia). Similar Triassic strata occur also in SouthAmerica (Argentina). 3Section IV.Palaeozoic Period.

The Primaryoflife,

all

strata are marked by Palaeozoic or ancient forms the species and all but sixteen genera then existing

being now extinct, as also certain whole families, viz. Graptolites, Rugose Corals, Cystideans, Trilobites and Eurypterids, OrthoCrinoids or ceratites and Labyrinthodont (or frog-like) reptiles. Encrinites and Brachiopod shells were then very abundant in number, and very varied in form. It was the age of Brachiopods. The fishes had heterocercal (unequally-lobed) tails, but no true bony skeleton, though often covered with bony plates. The land plants were chiefly Ferns, giant Lycopods, and Conifers. Note. Entire absence of flowering plants, birds, and mammals. 2

DYAS OR PERMIAN SYSTEM.The Carboniferous system in Britain is overlain by a great thickness of red sandstones, shales, limestones, and marls which was formerly considered to be one system and was named the New

Red Sandstone.

Subsequently,

it

was found to be composed

of

two

distinct systems, the older of which is known as Permian and is 3 of Palseozoic age ; the younger, as Triassic, of Mesozic age. The advent of reptiles. Fossils are nearly confined to Fossils.

the marl, slate, and limestone bands. There are but few distinctive forms, most being mere survivals from the Carboniferous, which are of ordinary size in the lower beds but higher up become stunted

and

finally disappear.

2 3-

Vertebrata.slate,

Fishes

:

Palceoniscus,

and

copper

shales.

Platysomus, in the marl Labyrinthodonts JSranchiosaurus,:

Lepidotosaurus, and a true reptile (lizard), Proterosaurus. The Polyzoan Fenestella retiformis (fig. 54) ; Invertebrata. the Brachiopods, Productus (fig. 57) ; Spirifer (fig. 55) ; the Lamellibranchs, Bakevellia, Avicula, etc. Gasteropods are rare.

The Cephalopod Nautilus

(fig.

63).

In Great Britain and Europe Callipteris and Walchia Flora. are characteristic ; in Central India and southern hemisphereGlossopteris

and other Mesozoic types. 312

178Great Britain.

GEOLOGY FOE ENGINEERS.

[PT.

III.

CH. IX.

the east side of England, from the coast to the plains of the Trent, the Permian rocks consist of a great central mass of limestone ; but on the west side of the Pennines, and extending southwards into the centralof

On

Northumberland

counties, the calcareous zone disappears and we have a great accumulation of red, arenaceous, and gravelly rocks. The Lower division is typically developed in the Vale of Eden, where it consists of brick-red sandstones and breccias; the red rocks extend into the valleys of the Nith and Annan in Scotland, and the breccias, further south in Staffordshire, attain a thickness of 400 feet. The Upper division is best seen at St Bees, near Whitehaven. The Permian rocks of North Ireland consist of fossiliferous magnesian limestone with red marls at its base, and at the city of Armagh, of boulder beds and limestone breccias.

Products.

Some

of the finest building-stones of the country,

such as the Mansfield sandstones and the magnesian limestones of Durham, York, and Nottingham ; marls for brickmaking and a thick bed of rock-salt. 3 Continental Europe. In Northern Germany the Permian is made up of the Zechstein and Rothliegende, which constitute the so-called Dyassic type of the system. The Rothliegende occurs also in Bohemia, Saxony, the Saar district in S.W. Germany, and at many localities in Central France. In the typical Russian district of Perm the Permian strata cover vast areas, and consist of sandstones, limestones, and marls and shales in repeated In the Alps the Permian is represented by the alternation. Verrucano, and in the Tyrol by the sandstone and quartzporphyry series of Botzen, and by the richly fossiliferous marine In Carinthia and Sicily the entire series Bellerophon limestone.is

Copper-bearing deposits of Germany and Persia and coal-seams in France. North America. Permian rocks are rare. The highest division (the so-called Barren Measures) of the Coal Formation of the Alleghany region have been referred to the Permian, and contain an admixture of Coal Measure and Permain forms, In together with genera characteristic of the Jurassic period. Texas certain mottled clays, sandstones, and limestones, overlying the local Coal Measures, are referred to the Permian. Marine rocks of this age also occur in Spitzbergen? South America. Strata of the Indian Gondwana type with the GlossOpteris flora have been met with on the east of the Andes in Brazil and Argentina? Asia. In Southern India the Permian beds consist of great thicknesses of sandstones and shales, with fresh-water and

marine. Products.

many workable

SECT. IV.]terrestrial

THE GEOLOGICAL SYSTEMS.

179

the plants include Glossopteris and other fossils ; Mesozoic types, which are sometimes so abundant as to constitute valuable seams of coal. They form the lower half of the Gondwana series and comprise the Talcher, which is distinguished by its remarkable conglomerates or boulder beds (which are met with not only south of the Nerbudda River but in the Salt Range of the Punjab) and the Damuda with workable coal-seams. 3 The beds in South Africa are similar to those of Africa. South India. A group of sandstones and shales (Lower Karoo or Ecca beds), with local coal-seams, affords examples of Glossopteris and shows at its base a remarkable boulder bed (Dwyka) which has been compared with the Indian Talcher. 3 Similar beds to those of Southern India and Australasia. South Africa occur in Australia, hence it has been suggested thatthese three widely separated regions formed part of a single Permian continent. At Bacchus Marsh and elsewhere in Victoria sandstones and shales with the Glossopteris flora, associated with boulder conglomerates with striated pebbles, like those of the The Upper or Newcastle division of the Talcher, are met with.of

workable Coal Measures of New South Wales is also, probably, Permian age. In Queensland the local Permian is made up of a lower marine series with abundant Brachiopods and Cephalopods, and an upper fresh-water series with Glossopteris, etc. 3

CARBONIFEROUS SYSTEM.Fossils.

The age

of

Cryptogamic plants, Corals, and Crinoids.

the coal-bearing strata are marine, estuarine, and The marine forms are generically related to those terrestrial. of the Carboniferous Limestone, viz. abundant Corals, Encrinites,fossils of

The

Brachiopods, Cephalopods with rare Eurypterids, Phyllopods and Trilobites and occasionally Sponges, Annelids, and Scales and teeth of large Elasmobranch fishes are not Protozoa. uncommon. The estuarine forms include mussel-like forms, such as Anthrocosia. The terrestrial forms embrace rare forms of Articulata, such as scorpions, beetles, crickets, may-flies, etc., but the most abundant are plants including many Cryptogams and a few Gymnosperms. Among the Cryptogams are tree-like Lycopods,Polyzoa,3 Ferns, and Equisetums. Great Britain. This great system attains a maximum thickness of 20,000 feet and is made up of limestones, grits, Calcareous strata with sandstones, shales, coals, and ironstone. marine fossils prevail generally in the lower half of the system, and sandy and shaly strata with abundant land-plants in the upper half. The Upper Carboniferous or series of Coal Measures is djvide4

180

GEOLOGY FOR ENGINEERS.

[PT.

III.

CH. IX.

of the Millstone grit, The Middle or Grey which, however, is absent in the Midlands. Coal Measures afford the richest and most valuable seams of coal mined in the British coal-fields. Three of the chief British coalfields occur in the neighbourhood of the Bristol Channel ; six in the Midlands and the Welsh border ; five in the Pennine region ; three in Central Scotland ; and three in Ireland. In Southern Britain coal-measures have been proved to exist below some of the more recent formations. The Lower or Carboniferous Limestone series is typically developed in the Southern Pennines, where the Yoredale group of shales, limestones, and sandstones is from 1500 to 4500 feet thick and the limestone from 2000 to 4000. The same series recur in North Wales. In South Wales, Mendip Hills, and the Forest of Dean the Yoredale rocks are wanting. Passing northwards the limestone is gradually replaced by a series of sandstones, grits, and shales with occasional bands of limestone, which develops into the Calciferous group of sandstones, shales, and cement stones with a series of workable coals overlain by the Carboniferous Limestone, in the north of Scotland and north of Ireland. In Central Ireland the whole of the Lower Carboniferous is practically represented by limestones ; but in the extreme south of the island it becomes replaced by cleaved grits, sandstones, and In the central parts of Devonshire the whole of the shales. Lower and perhaps some of the Upper Carboniferous is represented by a mixed group of greywackes, flags, shales, and thin bands of limestone of the "Culm" type. 3 Continental Europe. Carboniferous strata of the Pennine type occur in Belgium and North France ; of the Culm type in West and North Germany, Central Europe, and the Alps ; and of The the Limestone (S. Wales) type in Russia and the Urals. chief European coal-fields are those of France and Belgium, Westphalia, Saarbriick, Silesia, Bohemia, and Russia, Central3 France, and Northern Spain. North America. Carboniferous rocks are grandly developed Their lower divisions in Nova Scotia and the United States. (sub-Carboniferous) are typically limestones, with abundant marine fossils ; and the beds of their highest division, which form the rich coal-fields of Nova Scotia, Pennsylvania, and the basins of the Ohio and Mississippi, are prolific in terrestrial plants

from the Lower by the arenaceous formation

and

afford

many remarkable

terrestrial Articulata. 3

Asia.

Carboniferous rocks,

covering large

areas,

occur

in

Northern China; they are made up of limestones below, with Fusulina, etc., rich coal-measures in the middle, and marine sandstones above. 3 Coal and Carboniferous limestone occur in

SECT. IV.]

THE GEOLOGICAL SYSTEMS.

181

Japan. Coal of this period is also found is some islands of the Indian Archipelago and in Borneo. 1 ^ Africa. Rocks with Carboniferous fossils occur in the Sahara and in Egypt? Coal has been noticed on the banks of the Zambesi, and occurs in the Transvaal and Orange River Colony. Natal coal is of Triassic or Permian age. 17 The Carboniferous rocks of New South Wales are Australia. formed of two distinct divisions, both containing workable coals. 3

DEVONIAN SYSTEM.There are two distinct types of strata: (1) the Types. Fresh-water or Old Red Sandstone, and (2) the Marine or Devonian. The age of Fishes and Eurypterids. Fossils.

Old Red Sandstone.

The Fauna is remarkable for the predominance of tishes. Their skeletons were cartilaginous, and their tails either diphyTheir bodies were sometimes naked, but more or hetero-cercal. 2 generally protected by an armour of plates, or a covering of granules, ganoid, or placoid scales, and in some cases were even provided with various protective spines (Ichthydorulites). The Old Red fishes included lamprey - like forms (Palceospondylus), fishes shell - skinned Ganoids (Ostracodermi), joint -necked (Coccosteus), fringe-finned Ganoids (Holoptychius, etc.), Dipnoids or mud-fishes (Dipterus, etc.), and shark -like Elasmobranchsthese fishes occur the giant Crustacea or Arachnoids Eurypterus (fig. 51), Pterygotus, and Stylonurus. The Flora are few in the Lower series and include Psilophyton and other marsh plants those of the Upper Old Red Sandstone;

(Acanthodes, etc.). Associated with

3

are

more common and embrace Lycopods and Ferns.Devonian.

Graptolites die out; a peculiar sponge, (?) Stromatopora, as do Corals (Favosites, fig. 44 ; Heliolites, fig. 45 ; " " Calceola, fig. 42), which form the Madrepore marble of Torbay and Plymouth. Trilobites are few, but large allied Crustaceans Brachiopod and Lamelli(Eurypterus, Pterygotus) continue. branch bivalve shells, and the Cephalopods, Orthoceras, Clymcnia, 2 Goniatites, Nautilus, are the most abundant fossils. Great Britain. The Old Red type occurs from the Bristol

abounds,

182

GEOLOGY FOE ENGINEERS.

[PT.

III.

CH. IX.

Channel through Wales, Central and North-East Scotland to the Shetlands j and also largely in Ireland. Everywhere a great break occurs between the Upper and Lower groups. It consists of lake deposits (in Lakes Orcadie, Lome, Caledonia, Cheviot, and Welsh lake), and in Scotland often abounds in fish remains and There, too, interbedded volcanic rocks occur, more land-plants. than 6000 feet thick, and form the Pentland, Ochil, and Sidlaw " the basal wrecks of extinct volcanoes." hills, which are The Devonian type occurs only to the south of the Bristol Channel, and consists of a great thickness of grey and blue slates, 2 schists, sandstones, and limestones rich in corals. Continental Europe. Old Red Sandstone strata occur in Northern Russia with typical fishes, in Norway with remarkable igneous rocks, and in Spitzbergen and Bear Island with abundant Devonian strata sweep almost uninterruptedly plant remains. Europe from Calais to the Urals. In Belgium and the through Rhine provinces all three divisions are present in great thickness and rich in characteristic fossils. In Russia they are almost horizontal, and interbedded with red sandy strata with Old Red In Bohemia they consist of limestones rich in Orthoceratites fishes. and Goniatites. Devonian rocks are also met with in many other3 parts of Europe.

North America. Old Red Sandstone beds are met with in Gaspe and New Brunswick, containing Lycopods, Calamites, Ferns, and even a few Conifers, often in such abundance as to form seams of coal. In the United States Devonian rocks include a Lower division of sandstones and limestones (Oriskany and Corniferous), with Brachiopods and plants a Middle division of black shales and limestones (Hamilton) with Goniatites and Productus; and an Upper division (Chemung) which is formed, in some districts, of limestones rich in Clymenia, and in others 3 of red sandstone (Catskill\ with Upper Old Red Sandstone fishes. strata are the source of immense The Devonian Products. supplies of petroleum which, it is thought, has distilled from decomposing animal matter in the limestones, such as fishes, crustaceans, and mollusca, whose hard parts are embedded in it;

in great abundance. bitumen. 5

This

is

also the source of the deposits of

(UPPER) SILURIAN SYSTEM.Fossils.

The age

of

and Trilobites ; and Insects. Scorpions,Encrinites,

Brachiopods ; advent of

abundanceVertebrates

of:

Corals,

Fishes,

The

Pteraspis,

Fishes are Elasmobrancliii or Ostracodermi (Cephalaspis^ The Arachnida or forms of scorpions appear. etc.).

SECT.

IV*.]

THE GEOLOGICAL SYSTEMS.

183

Amongare

Crustacea, Trilobites are abundant, Phacops, Calymene, and

Homalonotus being commonest.

Cephalopoda and Gasteropoda

Orthoceras and Betterophon (fig. 62). represented by Brachiopoda are the most prevalent and characteristic of the The Echinodermata system, especially Pentamerus and Spirifer. the are represented by star-fishes and crinoids, and of Of the Ccelenterata both Actinozoa and Hydrozoa are abundant. former the Corals are chiefly rugose, while in the latter the great group of Graptolites becomes extinct within the limits of the

system.

Of Flora but little is known ; but both Lycopods and Ferns 3 appear to have been in existence. Great Britain. The typical area is that of Shropshire, and the same type is prolonged south-westward along the Welsh border (where an older formation the Lower Llandovery makes its appearance at the base of the system), and south-eastward and eastwards into the areas of Woolhope, the Malvern Hills, and South Staffordshire, etc.strata of the greywacke type sweep through the parts of Wales from Cardigan to Denbigh, the Llandovery being represented to the south by great thicknesses of grits, and to the north by a few bands of graptolitic shales, while the equivalents of the Wenlock and Ludlow are more or less barren grits and shales, which thicken northwards (Denbigh Grits and Flags}. The same is the case in Westmoreland, where the Skelgill and Browgill Shales answer to the Llandovery, the Coniston Grits and Flags to the Wenlock, and the Bannister Slates and Kirkby Moor Flags to the Ludlow formations. Rocks of the greywacke type floor almost the whole of the Scottish uplands. The most widespread formation is the Gala Group (Tarannon), which is underlain by the thin but richly graptolitic formation of the Birkhill Shales (Llandovery), and overlain by another In greywack^ formation, the Riccarton Beds (Wenlock). Ireland, Silurian rocks of the Shropshire type occur in Galway and Kerry, and of the types of those of Birkhill and Gala of the

Silurian

central

southern uplands, in Londonderry, Cavan, and Down. 3 Continental Europe. In Northern Europe the Silurian rocks are usually limestones, as in Norway, Central Sweden, Gothland, and Esthonia, but are locally intermixed with or replaced by carbonaceous shales with graptolites, as in Scania and Dalecarlia. In Bohemia two lithological members occur, an Upper or CalIn France and careous series and a Lower or Graptolitic division. Belgium the Ludlow is partly represented by marls, and all the formations below by grey and black shales with graptolites. 3 North America. The majority of the rocks remind us both of

184

GEOLOGY FOR ENGINEERS.

[PT. III. CH. IX.

The Llandovery is reprethose of Shropshire and Scandinavia. sented by sandstones and shales (Oneida and Medina], the Wenlock by shales and calcareous beds (C'Union and Niagara], and the Ludlow by three formations the Salt Group of Onondaga, the Water-lime with Eurypterus, and Lower Helderberg limestones with abundant forms of Pentamerus. 3 Lower Silurian rocks occur in the Salt Range and Simla Asia. area, while in the great chain of the Himalayas, Silurian rocks, flanked by Secondary formations, form part of the central axis of the range. In China, Silurian Graptolites and Orthoceratites have been met with. Similar formations spread over large tracts in Southern Siberia, in the Altai Mountains, and in Asia Minor. 17 Australia. Silurian fossils occur in Southern and Western Australia, and it is in the highly metamorphosed Silurian rocks that auriferous quartz-veins so frequently occur. 17ORDOVICIAN OR LOWER SILURIAN SYSTEM.Silurian strata cover a wider extent of the earth's surface and are more uniform in nature of deposits and fossils than any other

group.

The age of Graptolites, Trilobites, and Cystideans. Fossils. Graptolites are the characteristic fossils ; they are found in more or less abundance in strata of all lithological types, but are most Of Trilobites the prevalent in the thin-bedded black shales. primordial genera Olenus, etc., die out, and Asaphus, Calymene,

2

and Ogygia Buchii first appear. Corals were few, but Brachiopods and Cystidean Echinoderms swarmed. Gasteropods first appear, also Cephalopod-chambered shells. 3 ex. Bellerophon Great Britain. The typical area is North Wales. The Arenig beds, containing enormous sheets of volcanic rocks, sweep round the Merionethshire anticlinal, forming the ranges of Cader Idris, the Arans, and the Arenigs, etc. They are succeeded by a great thickness of barren, dark shales, representative of the Llandeilo. The final division is made up of grey flagstones and shales with the typical Bala limestone near the base, and the Hirnant limeThe upper of the two volcanic groups of stone near the summit. the Ordovician of North Wales is comparatively thin near Bala, but expands to an enormous thickness, and forms the mountainIn the Lake District ranges of Snowdon and Penmaenmaur, etc. the two volcanic series are connected by intermediate masses of This lava and ashes and form collectively the Borrowdale series. is underlain by the Skiddaw slates and overlain by the Coniston In the Girvan district of South Scotland the lowest limestone. Ordovician rocks are the Ballantrae volcanic series. The Llandeilo;

SECT. IV.]

THE GEOLOGICAL SYSTEMS.

185

seems to be represented by the Stinchar group of conglomerates and limestones, and the Bala by the Ardmillan series of flagstones and shales. At Moffat, etc., the Upper Llandeilo and Bala beds are represented by the Glenkiln and Hartfell shales of the thinbedded Moffat series. In Tyrone In Ireland Ordovician rocks occur in many areas. and Mayo they are of the Girvan type in Down and Cavan they have a Moffat facies at Kildare and elsewhere in Central Ireland in they call to mind the Bala beds of the Lake District Wicklow and Wexford they are of the type of the sedimentary and volcanic rocks of North and South Wales. 3; ; ;

The Ordovician rocks attain their widest Continental Europe. Scandinavia and Esthonia, where they are thin, horizontal, and rich in fossils ; their calcareous members have a far more varied fauna than those of Britain, but their graptolitic members agree with ours almost specifically. The same is also the case in Belgium, but the rocks are more disturbed. Important beds occur in Western France and in Bohemia* North America. The Ordovician strata are of two main types the calcareous type of the central regions, including the Calciferous sandstone, the Chazy and Trenton limestones, and the Utica and Hudson River (Cincinnati group) shales and the greywacke and black-shale type of the Hudson River and the lower reaches of the St Lawrence, including the graptolite-bearing Quebec group (Point Levis beds) and the Marsouin and Norman's Kill shales,extension in;

etc. 8

Asia. Lower Silurian rocks occur in the Salt Range and the Simla area of India. 11 Ordovician strata with abundant Arenig and Australasia. Llandeilo graptolites are found in Australia (Victoria) and alsoin

New

Zealand. 3

CAMBRIAN SYSTEM.This system consists of a vast succession of reddishgrits, con-

glomerates, shales, slate, and quartzite ; but there is no gneiss, and there are few schists and fewer limestones. It is divided into5 Upper, Middle, and Lower zones.

Fossils.

The

genus Olenellus(fig.

(fig.

characteristic fossils are Trilobites, of which the 52) characterises the Lower, Paradoxides

The chief 53) the Middle, and Olenus the Upper Cambrian. invertebrate groups which occur, in addition, are Cephalopoda,Gasteropoda, Lamellibranchiata, Pteropoda, Brachiopoda, Asteroidea, Vertebrata are very doubtCrinoidea, Hydroida, and Sponges. fully represented ; and of plants only sea-weeds are known to

186

GEOLOGY FOR ENGINEERS.

[PT.

III.

CH. IX.

Great Britain. The Cambrian rocks of Merionethshire have been estimated at 15,000 feet in thickness. They consist of the Tremadoc slates, Lingula flags, Menevian beds, and Harlech series. At St David's (9000 feet thick) the Upper Cambrian is represented by the Tremadoc beds and Lingula flags, the Middle by the Menevian beds and Solva group, and the Lower by the Caerfai group, with evidences of Olenellus. In Shropshire the Cambrian consists of three members the

Wrekin quartzite at the base, the Cornley sandstone, and the Shineton shales. In the Malvern Hills the Cornley or Hollybush sandstone lies at the base of the Cambrian, and is followed by black shales with Dolgelly trilobites and green shales with In the Nuneaton district there are two members Dictyonema. In the Norththe Hartshill quartzite and Stockingford shales. west Highlands of Scotland a band of Cambrian strata ranges from Eriboll almost to Skye, comprising (1) Eriboll quartzite; (2) Fucoid beds; (3) Salterella grit; (4) Durness limestone. Near Bray Head in Ireland occur certain coloured slates and grits 3 usually referred to the Cambrian. Cambrian rocks are well displayed in Continental Europe. Scandinavia and North- West Russia ; they are usually horizontal and of no great thickness, but yield a rich fauna, the characteristic genera of the Lower, Middle, and Upper Cambrian being all Cambrian rocks occur in Bohemia, Bavaria, France, present.Belgium, Spain, and Sardinia. Asia. In India, Lower Cambrian fossils occur in the Salt Range of the Punjab, and Higher Cambrian fossils are met with in Northern China. 3 North America. Well developed in North America. The Lower Cambrian or Olenellus zone is shown in the Rocky Mountains, the Alleghanies, the Taconic Ranges, and in NewThe typical Middle Cambrian fossils are most foundland.3

abundant in New Brunswick (Acadia), Massachusetts, and Newfoundland. The Upper Cambrian (Potsdam sandstone, etc.) formations occur in Canada and in the basin of the Mississippi and the highest Cambrian or Dictyonema beds in the valley of;

the St Lawrence. 3 Australasia. Olenellus has been found in Western Australia.

Section V.

Eozoic Period.

ARCH^AN AND PRE-CAMBRIAN ROCKS.All rocks of greater antiquity than the oldest fossil-bearing strata of the Cambrian are grouped together as Pre-Cambrian or

SECT. V.]

THE GEOLOGICAL SYSTEMS.

187

Archaean. These rocks, unlike those of the subsequent fossiliferous systems, have not yet been satisfactorily divided into formations and systems. They present themselves under three types (a) coarsely crystalline gneisses and schists associated with plutonic igneous rocks ; (6) finely crystalline schists and gneisses associated with more or less metamorphosed sedimentaries and volcanics ; and (c) unaltered sediments and contemporaneous lavas, ashes,:

and

tuffs.

3

fossils yet obtained from the worm-burrows and worm-tracks. The crystalline limestone of the original Laurentian of North America have yielded the problematic fossil Eozoon Canadense, some of the more or less metamorphosed groups of the Huronian type, a few traces of Annelids, sponges, and plants and the unaltered 3 formations, forms of Protozoa, Mollusca, and Molluscoidea. Great Britain. In the North-West Highlands occur the Leivisian, which consists of coarsely crystalline gneisses and schists more or less inclined above which and unconformably rests the Torridonian, composed of masses of chocolate-coloured sandstones and conglomerates approximately horizontal. In Ireland there are gneissic rocks with micaceous and chloritic schists associated with granite in Wicklow, and gneisses and serpentinous limestones in Galway and Donegal, in all probability of Archaean age. In Wales occur the Dimetian, composed of granites and gneiss, covered by the Arvonian strata of volcanic rocks, and on the latter rest unconformably the Pebidian strata of slates and shales,

Fossils.

The only undisputedof Britain are

Pre-Cambrian rocks

\

;

etc.

Pre-Cambrian rocks occur in Anglesea, Shropshire (the Long-

myndian and Uriconian series), in the Malvern and at Charnwood Forest in Leicestershire. 3

Hills, at

the Lizard,

Continental Europe. Pre-Cambrian rocks of all the British types cover large areas in Scandinavia and Finland, occur also in France and Spain, and in the cores of the great European 3 mountain-ranges. " massifs " of Asia. In India there are two great gneissic and rocks the one forms the extensive upland and crystalline plateau tracts that extend from Ceylon through the Madras, Bengal, and Bundelkhand districts to Assam ; the other constitutes the colossal framework of the Himalayas. These Archaean gneisses are succeeded unconformably by a series 2000 feet thick ofquartzites, conglomerates, schists, slates, breecias, and limestones, associated with contemporaneous bedded igneous rocks. 17 North America. These rocks occupy a connected area of two million square miles, having Hudson Bay as its centre. They

188

GEOLOGY FOR ENGINEERS.

[PT.

III.

CH.

IX.

comprise a lower or Basement complex consisting of coarsely gneissose types, which was formerly called Laurentian, and an upper division known as AlgonJcian or Proterozoic which is divided into a Keewenawan, resting on an Upper and a Lower Huronianall of finer crystalline schists

South America.of Brazil,

and sediments, etc. 3 These rocks range through the greater part Guiana, and Venezuela and occur again in the Andes of

Pre-Cambrian rocks form considerable rocks tracts in 17 Algeria and on the eastern borders of Egypt. Australasia. Gneissic and crystalline rocks occupy large tractsin

Chili." Africa.

South -Western Australia.Zealand. 17

New

They

are also well developed in

PARTWHILE

IV.

GEOLOGICAL OBSERVATION.a theoretical knowledge of geology,as set forth verybriefly in the three preceding parts of this book, is of great value to the engineer as a necessary groundwork to any study of the

In the practical application of geology to engineering, which is the subject of the concluding part of this book, it is essential that the geological factors should be based on the most reliable data. Hence all geological observation must be carried on in the most accurate and careful manner possible. Every fact which throws light on the area observed must be carefully noted and the record must be both full and accurate. The observer should train himself not to jump to conclusions, but to view every bit of evidence with regard to the nature and structure of the rocks which are concealed from view, and must learn to interpret rightly such facts as are patent, without minimising their value or too greatly^

subject, the methods of geological observation, with in this part, are of fundamental importance.

which are dealt

exaggerating

it.

1

189

PT. IV. CH. X.

CHAPTER

X.

OUTDOOR WORK.EQUIPMENT.

equipment or outfit for the field should be one can do good work of any kind with a regular "Christmas tree" slung round him. The following instruments are, however, indispensable hammer, knife, lens, 1 compass and clinometer, note-book, and tape or other measure. Hammer. The most important implement of the geologist.ITis

essential that the

as light as possible.

No

:

It may be light or heavy, short- or long-handled, according to the nature of the work to be done and the fancy of the individual, but it must be heavy enough to break up any ordinary rock

which is met with. Most geologists recommend a square face with a chisel-shaped tail end, the cutting edge of the chisel being Sir A. Geikie at right angles to the axis of the handle shaft. considers a hammer weighing one pound, or a few ounces more, quite sufficient for the ordinary purposes of a field geologist but, when it is intended to collect specimens, a hammer weighing two or three pounds or even more will be required, and a small chipping or trimming hammer as well. If, therefore, the engineer has time and opportunity to devote to geological observation he will do well to collect rock specimens for future reference, and should 1 provide himself with both hammers. Chisel. geologists prefer to dispense with a Though many chisel, there is no doubt of its convenience where blocks of rock have to be worked out from a cliff-face, or in any place where t