424 Adhesion o f Earthy Malters i~ Slea~n Boilers.

very scarce, and consequently very dear, I was engaged in building, and, to save expense, I used English fir lbr spars and joists; but know- ing that tire English fit" was liable to the dry rot, the idea struck me that the steepin~ of it in lime and water might preserve it from early decay. [ tlmrefore had a trench dug, sufficiently long to admit the pieces of timber to lie in it, and tilled it with lime and water of the thickness of a puddle, in which I laid the timber cutup for use, and let it soak [or the space of a week; had the timber been larger, I should have allowed it to steep some time longer. It is now twenty- tive or thirty years since [ used this timber, and it is now as perfect- ly free from the dry rot as it was at that period,"

¶ On Preventing the etdhesion of an Earthy Crust to the inner Sur- face of Steam Boilers. By JA~,~ES B~DF0~m

[From the same.]

Almost all natural waters hold in solution both carbonale and sul- phate of lime, two earthy salts, of which the fbrmet + is thrown d o w n by bringing the water to a boiling heat, and the latter by evaporation. On t~s account it As, that ~f the mstde o[ a steam end, me hot er be e x - amined after having been in use for a few days, it will be found to contain muddy water, and an earthy crust will be seen adhering to the iron plates of which the vessel is formed. The rate at which this crust is deposited depends upon the hardness of the water etaploy ed, that is, on the proportion of the above mentioned earthy salts which it contains. This crust is a much worse conductor of heat titan i ron is, and therefore, a boiler lined with it, even to the thickness o f a tenth of an inch, possesses the following defects. The water which it contains is not so soon brought up to the boiling point, and a g rea te r quantity of fuel is re(luired to l)r°duce a given quantity of steam, he- cause a larger proportion of the heat given out during its burnit~g is carried up the chinumy and lost. I t becomes, therefore, necessary, from time to time, to remove this crust~ which is usually done by a hammer anti chisel; but this operation not only incurs a waste of time, but the boiler is often seriously injured, and rendered leaky by means of it.

It has been found that if a few potatoes are thrown into the boiler when it is again filled, after having been cleaned out, the formatioo, of crust is sensibly retarded, and that the adhesion of it to the sides of the boiler is greatly weakened, so as to allow of its being detached more speedily, and with much less hazard.

Another method of producing the same effect has been pointed out to the Society, by Mr. James Bedlbrd, of Leeds, druggist. He put into a large steam boiler between two and three gallons of sperm oil fools, and found that after eight weeks' constant use, the deposit of crust was very small compared to what it used to be from the same water alone, and also that tim crust could be cleared off by means o[ a common stiff broom. The application of oily matters lbr this put .

Wooden Road. 425

pose~ though original on the part of Mr. Bedford, is not absolutely new; for the Society have been informed b] one of their members, that he has known an iron boiler using Tliames water preserved in constant use for seventeen years by cleaning it often~ and smearing the inside with oil or tallow after each cleanir~g.

The Society, however, have reason to believe that neither of the above methods are in common use, and have, therefore, directed this short statement to be published for the benefit of those whom it may concern,

¶ Description of a ~boden Road. [From tile same.]

Blackheath IIiU, October 6, 1832.

Sn~,--I t is, doubtless, the duty of every traveller in foreign lands to observe attentively the improvements that have been made in use- ful arts in the variot]s places through which be may pass; and when he perceives any thing conducive to the happiness, comfort, or pros- perity of a people, unknown at home, to c,m~municate the same, for the general benefit of his fellow countrymen.

Under this impression, I take the liberty of soliciting that you will lay before the Society of Artu, &c. tile following account of-a mode of constructing roads in cities, hitherto totally unknown in England, and by far the~most perfect that has ever come under my notice. I think no person will deny that it is desirable to have the streets of towns so paved~ that in dry weather there should be no dust, and in wet weather no mud, and as little noise as possible fi'om the passing of carriages. All these advantages are combined in the kind of road I allude to, besides being smoother than a macadamized road, even when the latter is in its most perfect state.

In countries aboundin~ in wood, various schemes have been adopt- ed for the formation of roads of that material; but hitherto they have always been made by laying logs, or planks, parallel to, or at right angles with, the sides of the way; these logs were easily displaced, and soon cut up by the horses ~ hoofs~ and when once out of order, no road can possibly be worse. The improved road, on the contrary, will last five or six years without repair, and, were it not for the high price of timber in this country, might be adopted with the greatest advantage~ and being a plan of considerable natipnal utility, possibly tbe government might be induced to allow the~mportation of timber for this purpose, duty free.

Tim following instructions will be found sufficiently practical and explicit as a guide to the construction of roads on this principle.--

1. Prepare a hard and level bed of gravel, or broken stone, covered with sand, and well rolled~ about nine inches lower than the intended surface of the road.

~. Take logs of timber of sufficient diameter, and, by means of VoL. X I I I . - - N o . 6.~JunE~ 1834. 54