SOURCES OF HEAT 29 



Water has the highest specific heat of any known sub- 

 stance except hydrogen ; that is, it requires more heat to 

 raise the temperature of water a definite number of degrees 

 than it does to raise the temperature of an equal amount of 

 any other substance the same number of degrees. Practi- 

 cally this same thing can be stated in another way : Water in 

 cooling gives out more heat than any other substance in cool- 

 ing through the same number of degrees. For this reason 

 water is used in foot warmers and in hot-water bags. If 

 a copper lid were used as a foot warmer, it would give the 

 feet only .095 as much heat as water; a lead weight only 

 .031 as much heat as water. Flatirons are made of iron be 

 cause of the relatively high specific heat of iron. The 

 flatiron heats slowly and cools slowly, and, because of its 

 high specific heat, not only supplies the laundress with con- 

 siderable heat, but eliminates for her the frequent changing 

 of the flatiron. 



1 8. Water and Weather. About four times as much heat is 

 required to heat a given quantity of water one degree as to 

 heat an equal quantity of earth. In summer, when the rocks 

 and the sand along the shore are burning hot, the ocean and 

 lakes are pleasantly cool, although the amount of heat pres- 

 ent in the water is as great as that present in the earth. In 

 winter, long after the rocks and sand have given out their 

 heat and have become cold, the water continues to give out 

 the vast store of heat accumulated during the summer. This 

 explains why lands situated on or near large bodies of water 

 usually have less variation in temperature than inland regions. 

 In the summer the water cools the region ; in the winter, on 

 the contrary, the water heats the region, and hence extremes 

 of temperature are practically unknown. 



19. Sources of Heat. Most of the heat which we enjoy 

 and use we owe to the sun. The wood which blazes on the 



