OF THE ATOMIC THEORY. 33 



and the peroxide of iron will be a compound of 

 2 atoms iron, and 3 atoms oxygen. 



It is by no means unlikely, that this last 

 method may represent the true composition of 

 this oxide, and of the other compounds into 

 which half an atom of oxygen, or of an acid or 

 base, appears to enter. Nevertheless, I have been 

 induced to represent the compound in the first 

 way rather than the second ; because it gives us 

 smaller and simpler numbers, and enables us 

 better to see the connection between the com- 

 pound in question, and other compounds of the 

 same constituents. If we represent the atomic 

 weights of iron and its oxides as follows, 



Iron . . . 3-5 

 Protoxide of iron . 4-5 

 Peroxide of iron 5*0 



we see at a glance that the protoxide is a com- 

 pound of 1 atom iron + 1 atom oxygen ; and 

 that the oxygen in the peroxide is to that in the 

 protoxide, as 3 to 2. But if we represent these 

 atomic weights by 



Iron . . 3'5 



Protoxide of iron . 4-5 

 Peroxide of iron . 10.0 



by doubling the number of atoms in the perox- 

 ide, the relation between the oxygen, in the two 

 oxides of iron, is much less evident. For the 



VOL. I. C 



