The temperature 62° F. is the temperature of water used in calculating the specific gravity of bodies, with respect to the gravity or density of water as a basis, or as unity. _Weight of one cubic foot of Pure Water._ At 32° F. = 62·418 pounds. At 39°·1. = 62·425 „ At 62° (Standard temperature) = 62·355 „ At 212° = 59·640 „ The weight of a cubic foot of water is, it may be added, about 1000 ounces (exactly 998·8 ounces), at the temperature of maximum density. The weight of a cylindrical foot of water at 62° F. is 48·973 pounds. _Weight of one cubic inch of Pure Water._ At 32° F. = ·03612 pound, or 0·5779 ounce. At 37°·1 = ·036125 „ „ 0·5780 „ At 62° = ·03608 „ „ 0·5773 „ or 252·595 grains. At 212° = ·03451 „ „ 0·5522 „ The weight of one cylindrical inch of pure water at 62° F. is ·02833 pounds, or 0·4533 ounce. _Volume of one pound of Pure Water._ At 32° F. = ·016021 cubic foot, or 27·684 cubic inches. At 39°·1 = ·016019 „ „ 27·680 „ At 62° = ·016037 „ „ 27·712 „ At 212° = ·016770 „ „ 28·978 „ The volume of one ounce of pure water at 62° F. is 1·732 cubic inches. The weight of water is usually taken in round numbers, for ordinary calculations, at 62·4 lbs. per cubic foot, which is the weight at 52°·3 F.; or it is taken at 62-1/2 lbs. per cubic foot. Salt water boils at a higher temperature than fresh water owing to its greater density, and because the boiling point of water is increased by any substance that enters into chemical combination with it. The density of water decreases as the temperature increases, since heat destroys cohesion and expands the particles, causing them to occupy greater space, where precision is not required; the pressure on a square foot at different ocean depths are approximate, in the following TABLE. Depth in feet. | Pressure on sq. foot. ===============+====================== 8 | 500 lbs. 16 | 1000 „ 24 | 1500 „ 32 | 2000 „ 40 | 2500 „ 48 | 3000 „ 56 | 3500 „ 64 | 4000 „ 72 | 4500 „ 80 | 5000 „ 88 | 5500 „ 96 | 6000 „ ---------------+---------------------- 1 mile, or 5,280 feet, 330,000 lbs. 5 miles, 1,650,000 „ This table is based upon an allowance of 62-1/2 lbs. of water to the cubic foot, thus 8 feet × 62-1/2 = 500, etc. HYDRAULIC DATA. _Water is practically non-elastic._ A pressure of 30,000 lbs. to the square inch has been applied and its contraction has been found to be less than one-twelfth. Experiment appears to show that for each atmosphere of pressure it is condensed 47-1/2 millionth of its bulk.