ATOMIC THEORY. 119 



Hydrogen . . 12.5 



Carbon . . . 76.4 



Chlorine . . 442.6 



Lead . . . 1294.5 



The numbers belonging to the other or hydrogen series,, are 

 all twelve and a half times less than the corresponding numbers 

 of the oxygen series, into which the former may most easily be 

 converted by multiplying them by one hundred, and dividing 

 the product by eight. Or the numbers of the oxygen may be 

 reduced to the hydrogen scale, which many prefer, by dividing 

 them by one hundred, and multiplying the quotient by eight. 

 The numbers of the hydrogen scale are of a lower term, smaller 

 and more easily recollected than the oxygen series, but their 

 fractional portion can seldom be neglected in computing by 

 means of them, and the insecurity of the basis on which this se- 

 ries rests is a great objection to its adoption. There is an actual 

 experimental difficulty in determining the equivalent of hydro- 

 gen with precision, arising from its extreme smallness ; so that 

 this equivalent itself is more liable to correction and alteration 

 than most others, which would necessitate a corresponding 

 change throughout the whole scale. 



ATOMIC THEORY. 



The laws of combination and the doctrine of equivalents which 

 have just been considered, are founded upon experimental evi- 

 dence only, and involve no hypothesis. The most general of these 

 laws were not however suggested by observation, but by a theory 

 of the atomic constitution of bodies, in which they are included, 

 and which affords a luminous explanation of them. The partial 

 verification which this theory has received in the estab- 

 lishment of these laws, adds greatly to its interest, and is a 

 strong argument in favour of its truth. It is the atomic theory 

 of Dalton, the essential part of which may be stated in a few 

 words. 



Although matter appears to be divided and comminuted in 

 many circumstances to an extent beyond our powers of concep- 

 tion, it is possible that it may not be indefinitely divisible ; that 

 there may be a limit to the successive division or secability of 

 its parts, a limit which it may be difficult or impossible to reach 

 by experiment, but which nevertheless exists. Matter may 



