 The sleepers are very broad, and only 18 inches from centre to centre.A rail of foreign fir, 4 inches square, is pinned down to them, and another rail, of the same dimensions, is laid over it, and the whole well beat up in good clay; on the top of the upper rail is laid a bar of malleable iron, of 1¾ inches breadth, and nearly six-8ths thick.The waggons have cast iron wheels, 27½ inches diameter, and are supposed to weigh altogether about a ton.