If equal amounts of copper and water are heated, it becomes evident that it takes a great deal more heat to raise 1 lb. of water 1° F. than to raise 1 lb. of copper. The unit of heat has already been defined as the amount of heat necessary to raise the temperature of 1 lb. of water 1 F. The quotient obtained by dividing the amount of heat required to raise the temperature of the substance one degree Fahrenheit and that required to raise the temperature of an equal mass of water one degree is called the specific heat of the body. To illustrate: The specific heat of lead is .031 while the specific heat of water is 1. This means that it would require 31 times as much heat to raise 1 lb. of water one degree in temperature as it would to raise the temperature of 1 lb. of lead one degree.

The following table gives the specific heat of the different substances in which the mechanic and engineer are most interested.

Table of Specific Heat

Water at 39.1° F......

1. 000

Ice at 32° F..........

504

Steam at 212° F......

480

Mercury.............

033

Cast ron......................

.130

Wrought Iron........

113

Soft Steel............

.110

Copper...........

.095

Lead.....................

031

Coal..............

.240

Air...............

238

Hydrogen...............

404

Oxygen...........

.218

Nitrogen..........

.244