1 foot head = 0·434 lb. per square inch. 1 lb. per square inch = 2·31 ft. head. 1 imperial gallon = 277·274 cubic inches. 1 imperial gallon = 0·16045 cubic foot. 1 imperial gallon = 10 lb. 1 cubic foot of water = 62·32 lb. = 6·232 imperial gallons. 1 cubic foot of sea water = 64·00 lb. 1 cubic inch of water = 0·03616 lb. 1 cubic inch of sea water = 0·037037 lb. 1 cylindrical foot of water = 48·96 lb. 1 cylindrical inch of water = 0·0284 lb. A column of water 12 in. long 1 in. square = 0·434 lb. A column of water 12 in. long 1 in. diameter = 0·340 lb. Capacity of a 12 in. cube = 6·232 gallons. Capacity of a 1 in. square 1 ft. long = 0·0434 gallon. Capacity of a 1 ft. diameter 1 ft. long = 4·896 gallons. Capacity of a cylinder 1 in. diameter 1 ft. long = 0·034 gallon. Capacity of a cylindrical inch = 0·002832 gallon. Capacity of a cubic inch = 0·003606 gallon. Capacity of a sphere 12 in. diameter = 3·263 gallons. Capacity of a sphere 1 in. diameter = 0·00188 gallon. 1 imperial gallon = 1·2 United States gallon. 1 imperial gallon = 4·543 litres of water. 1 United States gallon = 231·0 cubic inches. 1 United States gallon = 0·83 imperial gallon. 1 United States gallon = 3·8 litres of water. 1 cubic foot of water = 7·476 United States gallons. 1 cubic foot of water = 28·375 litres of water. 1 litre of water = 0·22 imperial gallon. 1 litre of water = 0·264 United States gallon. 1 litre of water = 61·0 cubic inches. 1 litre of water = 0·0353 cubic foot. ───────────────────────────────────────────────────────────────────────── EQUIVALENTS OF POUNDS AVOIRDUPOIS. ─┬───────┬────────────┬────────────────┬────────────────┬──────────────── │ 10 │ 100 │ 1000 │ 10,000 │ 100,000 ─┼───────┼────────────┼────────────────┼────────────────┼──────────────── │qr. lb.│cwt. qr. lb.│ton cwt. qr. lb.│ton cwt. qr. lb.│ton cwt. qr. lb. 1│ 0 10│ 0 3 16│ 0 8 3 20│ 4 9 1 4│ 44 12 3 12 2│ 0 20│ 1 3 4│ 0 17 3 12│ 8 18 2 8│ 89 5 2 24 3│ 1 2│ 2 2 20│ 1 6 3 4│ 13 7 3 12│133 18 2 8 4│ 1 12│ 3 2 8│ 1 15 2 24│ 17 17 0 16│178 11 1 20 5│ 1 22│ 4 1 24│ 2 4 2 16│ 22 6 1 20│223 4 1 4 6│ 2 4│ 5 1 12│ 2 13 2 8│ 26 15 2 24│267 17 0 16 7│ 2 14│ 6 1 0│ 3 2 2 0│ 31 5 0 0│312 10 0 0 8│ 2 24│ 7 0 16│ 3 11 1 20│ 35 14 1 4│357 2 3 12 9│ 3 6│ 8 0 4│ 4 0 1 12│ 40 3 2 8│401 15 2 24 ─┴───────┴────────────┴────────────────┴────────────────┴──────────────── TRIGONOMETRICAL FUNCTIONS. RIGHT-ANGLED TRIANGLES. [Illustration: [Right-angled Triangle]] Sin. A = (_a_)/(_b_) Sec. A = (_b_)/(_c_) Tan. A = (_a_)/(_c_) Cos. A = (_c_)/(_b_) Cosec. A = (_b_)/(_a_) Cotan. A = (_c_)/(_a_)