SPECIFIC HEAT. 49 



for the water, the two would be brought to the same 

 temperature. In other words, mercury requires but 

 one-thirtieth as much heating as water, to make it 

 equally hot. It fills up, as it were, with heat, more 

 rapidly. The comparative quantity required by each 

 substance is called its specific heat. 



102. Taking water as the standard, and 

 callin g its specific heat one, that of mer- 



mercury? Of C ury is about one-thirtieth. That of iron 

 is about one-tenth. The specific heat of 

 other substances is given in decimals in a table con- 

 tained in the appendix. 



What is capa- 103. CAPACITY FOR HEAT. - If We COm- 



dty for heat ? p are e q ua i {mlks of water and' mercury, 

 instead of equal weights, AVC make out the specific 

 heat of mercury to be one-half instead of one-thirtieth. 

 The comparison is sometimes made in this way, but 

 the term capacity for heat, instead of specific heat is 

 always employed in such cases. Thus, we say that 

 water has twice the capacity of mercury for heat. 

 ,, . . .. 104. RELATION OF HEAT AND DENSITY. 



W liat relation 



exists between If water were suddenly converted into 



density and , , -i -i -i 



capacity for niercury, much heat would be given out, 

 heat? as j s evident from what has already been 



stated. So when a metal is hammered, the capacity 

 of the denser metal for heat being less, the surplus 

 goes to make it sensibly hotter. In other words, in 

 proportion as density is increased in any substance, its 

 capacity for heat is diminished, and vice versa. It is 

 not, however, to be understood that the comparative 

 capacity for heat in different substances is always in 



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