The weight will depend upon the specific gravity of the granite, and the closeness with which the material is packed together; as ordinarily thrown together after breaking, the voids will be from 25 per cent, to 33 per cent, of the whole, and the weight of a cubic yard will be from 274 cwt. to 30cwt. A waggon 12 ft. Sin. by 5 ft. 8 in. by 1ft. l0in, will contain 4, cub. yd., or from 6 3/4 tons to 7 4/3 tons. The probable weight may be ascertained by filling a water-tight box with the macadam, and pouring in measured quantities of water until all the voids are full. The cubic contents of the water -i- cubic contents of the box = percentage of voids. The weight per cubic foot of the granite being known, it is easy to calculate the weight of a cubic yard of macadam.