42 mature'e 



of it, he would better tell what he does not 

 know about it, for in that way he can make a 

 volume of almost any size. But if he wants 

 to tell what it really is, and what he really 

 knows it is, a primer will be large enough. 

 This much we know that it is one of many 

 expressions of energy. 



Chemistry teaches that heat is directly re- 

 lated to the atoms of matter. Atoms of dif- 

 ferent substances differ greatly in weight. For 

 instance, the hydrogen atom is the unit of 

 atomic weight, because it is the lightest of all 

 of them. Taking the hydrogen atom as the 

 unit, in round numbers the iron atom weighs 

 as much as 56 atoms of hydrogen, copper a 

 little over 63, silver 108, gold 197. Heat acts 

 upon matter according to the number of atoms 

 in a given space, and not as its weight. Know- 

 ing the relative weights of the atoms of the 

 different metals named, it would be possible 

 to determine by weight the dimensions of 

 different pieces of metal so that they will con- 

 tain an equal number of atoms. If we take 

 pieces of iron, copper, silver and gold, each of 

 such weight as that all the pieces will contain 

 the same number of atoms, and subject them 

 to heat till all are raised to the same temper- 

 ature, it will be found that they have all ab-, 

 sorbed practically the same quantity of heat 

 without regard to the different weights of mat- 

 ter. It will be observed that the piece of sil- 



