Many experiments have shown that the power of absorption of sand decreases with the fineness of the grain, and that sand when thoroughly wet will contain water equal to about one-third to two-fifths of its bulk, and that almost all this can be drained; hence its varying condition and instability. If a well be sunk in sandstone and regularly pumped it will drain the rock around for some distance, the drainage space being conical, its vertex the bottom of the well, and its base the surface, varying in extent according to the nature of the soil and depth of well, showing the porous nature of sand. The interstices of silicious sea-sand, when not compressed, have been ascertained by Mr. J. Watt Sandeman, M. Inst. C.E., to amount to about 40 per cent. of the volume of sand. For coarse or fine sand, or a mixture of the two, the interstices did not vary much. When it was compressed by a rammer in water, its bulk could be reduced to the extent of 12½ per cent. The interstices of broken red sandstone, varying in size to that which would pass through an 8-inch ring, were found to be 36 per cent. of the whole volume, but as the stones were in contact 10 per cent, must be added, and if under water 15 per cent. Per cent. of the interstices. Broken Welsh limestone to pass a 3-inch ring 50·9 Gravel, free of sand. Small pebbles to pieces gauged by a 33·6 25-inch ring Welsh limestone and gravel as above mixed in equal 34·0 proportions Mason’s shivers of Anglesey limestone, small gravel to 48·0 pieces gauged by a 4-inch ring Runcorn red sandstone, large, varying in size from pieces 50·0 to pass a 4-inch ring to an 8-inch ring Ditto, small, varying in size from sand to pieces gauged 34·0 by a 4-inch ring The two preceding when mixed in equal proportions 36·0 The experiments clearly show the known great capability of subsidence in sandy and open sandy gravel soils, their clear water space, and how easily fine sand may, by a current of water, become running sand, and their adaptability for ramming and consolidation by moisture. Tipped sand when rammed will subside if saturated with water nearly as much as it can be beaten down, which shows how greatly its bulk is affected by water, and although its rapid consolidation is an advantage in embankments, it is of importance that percolation should be equal.