EXCURSION TO PONDERS END.

SATURDAY, APRIL 3RD, 1909.

Directors: W. WHITAKER, B.A., F.R.S., F.G.S., andA. S. KENNARD, F.G.S.

Excursion Secretary: Miss M. S. JOHNSTON.

eN,port by A. S. KENNARD)

A LARGE party assembled at Liverpool Street Station, and by thekindness of Mr. Wilson, engineer to the Great Eastern Railway, someof them inspected a few Pleistocene remains lately found in the low­level gravel near Ponders End Station. The remains comprisedfour teeth of the mammoth (Elephas primigenius) and a small butexceptionally well-preserved tusk belonging to the same species.The members then took train to Chingford, where their numberswere increased to forty, and proceeded to the excavations in thevalley of the Lea.

Here Mr. Whitaker pointed out the chief geological featuresof the neighbourhood, and described the works which were inprogress. In order to construct this new reservoir it has beennecessary to divert the River Lea (not to be confounded withthe Lea Navigation Canal, usually called the" Barge River "),

Mr. Whitaker stated that in such works great alterationsin the country are made, roads are diverted, and even countyboundaries are obliterated. M1'. Whitaker also remarked onthe noteworthy erosion of the valley. On the Middlesexside are extensive and nearly flat deposits of gravel and brick­earth representing the former channels of the river, whilst onthe Essex side there were scarcely any fluviatile deposits, thus clearlyshowing that the river has been gradually leaving the right(western) bank and cutting away the left bank, and as additionalevidence of this he pointed out the occurrence of landslips in theLondon Clay on the left bank. Mr. Kennard then explainedthat there was evidence from trial-borings of the existence of theold buried channel which had been noted lower down the valleyat Tottenham, for in one case 30 ft. of alluvial deposits had beenproved.

The Members then examined the puddle-trench which wasbeing made, and the method of construction was described byMr. Atkins and Mr. Whitaker, after which the party proceededalong the new channel which was in process of excavation. At firstthe sections showed about two feet of marsh-clay overlying onefoot of Pleistocene brick-earth resting on gravel. The marsh-clay

ExCURSION TO PONDERS END. 173

soon increased in thickness and the Pleistocene brickearthdisappeared. The sections were now about 5 ft. in depth,showing marsh-clay and at the base a calcareous marl. Shellswere by no means abundant, and the deposit was probablya cham-marl. At the northern part of the section aboutr a ft, of alluvial deposits were visible, an impure peat being thelowest bed; but this was very close to the old channel, and therewas abundant evidence of human occupation in the upper part, inthe shape of modern piling, &c. Mr. Kennard, in describing theshell -marl, stated that, with one exception, all the shells found inthese beds are of species still living in the neighbourhood, the oneextinct form being Planorbis stroemii, West. This species isparticularly abundant in the older Holocene beds of the Thamesand the Lea, but it had apparently become extinct in Romantimes. It is still living in Sweden, and is known from theHolocene of Denmark and Germany. Another noteworthy formwhich he had found was Vertigo mouiinsiana, Dupuy, a localshell which still lives at Broxbourne. The party then returned toChingford and partook of tea at the" Bull and Crown," where ahearty vote of thanks was passed to the Directors.

REFERENCES.

Geological Survey Map, Sheet 1 ; N .W. or London District, Sheet 2.Ordnance Map, Sheet 256.1872. WHITAKER, W.-" Geology of London Basin." Mtm. Gtot. SurvIY.

vol, iv,1884. SMITH, W. G._" On a Pal eeolithic Floor in North-East London."

Journ. Anthro», Instit., vol. xiii.1889. WHITAKER,W.-" Geology of London." lrftm. GIOt. Suro., vol. i, pp.

450,47 2 .1890. WOODWARD, B. B._" On the Pleistocene Non-Marine Mollusca of

the London District." Proc. Geoi. Assoc., vol . xi , p. 349(part 8, 2S.).

1897. KENNARD, A. S., and woonwaao, B. B._" The Post Pliocene Non­Marine Mollusca of Essex." Essex 1\'al., vol. x, p. 9I.

1897. WILSON, T. HAY.-" Note on Sections in the Lea Valley at SouthTottenharn.' Essex Nat., vol. x, p. IIO.

1903. KENNARD, A. S., and WOODWARD. B. B.-" The Non-MarineMollusca of the River Lea Alluvium at Walthamstow, Essex."Essex Nat ., vol. xiii, pp . 13-21.