OF RAIL-ROADS.

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phery of the wheel would be altered, beingmade quite flat and of less breadth; and,the rim of wheel, for the edge-rail, was againbrought back to the same form as that for thewooden Rail-road.

Fig, IX. Plate I. Represents an elevation or side-viewof the edge-rail, as mostly used in late years, which consistsof a bar of cast-iron, from' three to four feet long, and aboutone-half or three-quarters of an inch thick, swelling out at.the upper part to two or two inches and half broad, for thewheel to run upon, and placed upright, within a sort of chair,upon the stem supports. These rails, when first used, werenot secured upon the stone or wooden sleeper by a separatechair or pedestal, but had a flat bearing projecting outwards,on each side, at the end of the rail, through which weresquare holes for the pins or nails to pass, that fastened themto the sleepers.

It is evident that this form of rail combinesthe greatest strength with the least expenditureof material; for, being placed upright, theypresent the greatest depth in the direction ofthe stress or strain upon them. The form firstused was nearly a parallelogram. Fig. Ill. PlateII. will show a section of those at present used,the breadth of the upper surface, a, is about twoinches and a half; after keeping this breadth alittle way down, as shewn in the drawing, theygradually diminished to three-quarters, taperingdown to half an inch, near the bottom at c; thiswas the section of them for a long period, but

D