DALTOX. 51 



We perceive that, although our dippings have been quite 

 at random, we get no fractions of an ounce no halves and 

 quarters, and so forth. Moreover, the results of the five 

 weighings seem to prove that each of the bullets weighs 

 exactly one ounce ; and if similar results accrued from any 

 number of weighings, that which was at first a notion would 

 grow into an irresistible conviction. Observe what comes 

 of this. There are sixty and more known kinds of matter, 

 in respect of which Dalton perceived that, weigh them, tor- 

 ture them, analyse them as he might, his weighings, tortur- 

 ings, and analyses disclosed no fractions. How can this fact 

 be explained, except on the assumption that matter is com- 

 posed of ultimate atoms ? 



If we now assume, in place of the existence of one set 

 of bullets of one weight and one substance, the existence of 

 sixty and more* different kinds of bullets, differing from each 

 other in weight ; so that, calling the weight of the lightest 1, 

 the weight of the heaviest would be 213, we arrive at a still 

 nearer idea of the conditions of the atomic theory. 



It so happens that each kind of matter has its own ap- 

 pointed work to do ; and that one kind of matter can do the 

 work, or fill the place of another kind. Thus, to give an ex- 

 ample in the language of chemistry, chlorine can unite with 

 hydrogen, and so can oxygen ; but whereas exactly eight parts 

 by weight of oxygen are required by exactly one part by 

 weight of hydrogen to generate water, it takes thirty-six parts 

 by weight of chlorine to be equivalent for, or take the place 

 of, the aforesaid eight parts by weight of oxygen, and, by 

 combining with the one part by weight of hydrogen, to form 

 hydrochloric acid. So 1, 8, and 36, are saidj to be the equi- 

 valents or atomic numbers of hydrogen, oxygen, and chlorine 



* The exact number of elementary bodies is still undetermined : sixty- 

 three is usually accepted. 



f Or mere said. It is usual now to regard the atomic weight of oxygen 

 as 16, on which assumption water is composed of two hydrogen combined 

 with one oxygen. 



