Note 13 — The Correlation of Vital and Physical Forces.

The unit of impact being that given by a body weighing one pound and moving one foot a second, the impact of such a body falling from a hight of 772 feet—the velocity acquired being 222¼ feet per second (=√(2sg))—would be 1 × (222¼)2 = 49,408 units, the equivalent in impact of one heat-unit. A cannon-ball weighing 1000 lbs. and moving 1100 feet a second would have an impact of (1100)2 × 1000 = 1,210,000,000 units. Dividing this by 49,408, the quotient is 24489 heat units, the equivalent of the impact. The specific heat of iron being ·1138, this amount of heat would raise the temperature of one pound of iron 215.191° F. (24,489 × ·1138) or of 1000 pounds of iron 215° F. 24489 pounds of water heated one degree, is equal to 136½ pounds, or 17 gallons U. S., heated 180 degrees; i.e., from 32° to 212° F.