broken small; or good gravel, sm or depth. On this bed must Dr blocks to fasten the rails stone in all places where it can at d of sufficient size. They show ends of two rab the proper pos The rails yard in leug edge about and three a best maur the w gener brua:: 10 al Your in the tion, aland with asily conine of that nade the exSubstance. It ich come from insect; the one Dun into a thread; ents as taken from un it. I suspect it ot of the same genus be found greater than could be wished. On a railway on the improved plan, where the descent is more than as i to 50, six or eight waggons, loaded with 30 or 40 hundred weight each, will have such a tendency to run downwards, as would require great labour of one horse to check and regulate, unless that tendency were checked by sledging some of the wheels. On such, and steeper roads, iron slippers are applied, one or more to a gang of waggons, as occasion may require; each slipper being chained to the side of one of the waggons, and, being put under the wheel, forms a sledge. Where the descent is very great, steep inclined planes, with machinery, may be adopted, so as to render the other parts of the rail-way easy. On such inclined planes, the descending loaded waggons being applied to raise the ascending empty, or partly loaded ones, the necefsity of sledging the wheels is avoided ; and the labour of the horse greatly reduced. 4 To obtain the desired levels, gentle descents, or steep inclined planes; and to avoid sharp turns and circuitous tracts, it will often be found prudent to cross valleys by bridges and embankments; to cut through ridges of land; and in very rugged countries short 'tunnels may sometimes be necessary. The line of rail-way being fixed, and the plans and sections by which the same is to be executed settled, the ground for the whole must be formed and effectually drained. The breadth of bed for a single rail-way should be, in general, four yards; and for a double one six yards, exclusive of the fences, side drains, and ramparts. The bed of road so formed to the proper inclination, and the embankments and works thereof made firm, the surface must be covered with a bed of stones broken small; or good gravel, six inches in thickness or depth. On this bed must be laid the sleepers or blocks to fasten the rails upon. These should be of stone in all places where it can be obtained in blocks of sufficient size. They should be not less than 8, nor more than 12 inches in thickness; and of such breadths (circular, square, or triangular) as shall make them 150lbs. or 200lbs. weight each. Their shape is not material, so as they have a flat bottom to rest upon, and a small portion of their upper surface level, to form a firm bed for the end of the rails. In the centre of each block must be drilled a hole, one inch and a half diameter, and six inches in depth, to receive an octagonal plug of dry oak five inches in length; for it should not reach the bottom of the hole; nor should it be larger than so as to be put in easily, and without much driving: for, if too tight fitted, it might, when wet, burst the stone. These plugs are each to receive an iron spike or large nail, with a flat point and long head, adapted to fit the counter-sunk notches in the ends of two rails, and thereby to fasten them down in the proper position. The rails should be of the stoutest cast iron, one yard in length each, formed with a flanch on the inner edge about two inches and a half high at the ends, and three and a half in the centre; and shaped in the best manner to give strength to the rails, and keep the wheels in their track. The soles of the rails, for general purposes, should not be lefs than four inches broad; and the thickness proportioned to the work they are intended for. On rail-ways for heavy burdens, great use, and long duration, the rails should be very an hundred weight, each. For rail-ways of lefs consequence lefs weight of metal will do; but it will not be prudent to use them of less than 30lbs. weight each, in any situation exposed to breakage above ground*. In fixing the blocks and rails, great attention is required to make them firm. No earth or soft materials are to be used between the blocks and the bed of small stones or gravel, on which the rails must all be fixed by an iron gauge, to keep the sides at a regular distance, or parallel to each other. The best width of road for general purposes is 4 feet 2 inches between the flanches of the rails; the wheels of the carriages running in tracks about 4 feet 6 inches asunder. Rails of particular forms are necefsary where roads branch out from, or intersect each other; and where carriage roads cross the rail-ways; and at turnings of the railways, great care is required to make them perfectly easy. The rails of that side forming the inner part of the curve should be fixed a little lower than the other; and the rails should be set a little under the gauge, so as to bring the sides nearer together than in the straight parts: these deviations in level and width to be in proportion to the sharpnefs of the curve. The blocks and rails being fixed and spiked fast, nothing more remains to be done than to fill the horse path, or space between the blocks, with good gravel, or other proper materials; a little of which must also be put on the outsides of the blocks, to keep them in * In mines, and other works under ground, where very small carriages only can be employed, very light rails are used, forming what are called train roads, on a system introduced by Mr. Carr; and these kindsof light rail-ways have been much used above ground in Shropshire and other counties where coals and other minerals are obtained. their proper places. This gravel should always be kept below the surface of the rails on which the wheels are to run, to keep the tracks for the wheels free from dirt and obstructions. The form of the rails must be such as will free them from dirt if the gravelling is kept below their level. In the constructing of the carriages great attention to avoid friction is necessary, particularly in the formation of the wheels and axles, which must be adapted to the sort of rail-ways and the kind of loading; and for which, general directions cannot be given within the limits of this paper. To the Editor of Recreations in Agriculture, &c. February 9, 1801. SIR, As correcting of error contributes to the improvement of knowledge, I thank an Old Waltonian for his hints respecting the Indian weed in your last Number, page 395, which I before, walking in the old trammels of prejudice through misinformation, always considered as a vegetable production, and with some diffidence (for old prejudices are not easily conquered) reflected thereon; but, having a line of that denomination, I was not long before I made the experiment, and found it truly of animal substance. It appears to me that there are two sorts which come from China, the production of the same insect; the one taken out of the caterpillar before it be spun into a thread; the other combined of several filaments as taken from the web after the caterpillar has spun it. I suspect it to be the production of an insect of the same genus |