To find the contents of cylindrical vessels in cubic inches, square the diameter of the vessel in inches (that is, multiply it by itself), and then multiply by "7851 and by the height in inches. To find the contents in cubic feet, take all dimensions in feet. Knowing the contents in cubic inches, divide by 277.274to find the contents in gallons. Dviding the contents in cubic feet by •16015 answers the same purpose. Shorter methods will suggest themselves from the following. A cylinder 1 ft. in diameter and 1 ft. long will hold4.'89 gal., and a cylinder 1 in. in diameter and 1 ft. long will hold .031 gal. Also, capacities vary with the lengths of the cylinders and with the squares of the diameters. Thus a cylinder 1ft. in diameter would hold 12 x 12 =114 times the contents of a cylinder of equal length but 1 in. in diameter.