120 ATOMIC THEORY. 



therefore be composed of ultimate particles or atoms, which are 

 not farther divisible, and each of which possesses a certain 

 absolute and possibly appreciable weight. Now the question 

 arises, is the atom in every kind of matter of the same weight, 

 or do atoms of different kinds of matter differ in weight ? Are 

 the ultimate particles, for instance, to which charcoal and sul- 

 phur are reducible, of the same or of different weights? Let their 

 weights be supposed to be different, to be in the proportion of 

 the equivalent numbers of sulphur and charcoal, which thus 

 become atomic weights, and so of the atoms of other elementary 

 bodies, and the whole laws of combination follow by the simplest 

 reasoning. The atoms of the elementary bodies may be repre- 

 sented to the eye by spheres or by circles in which their sym- 

 bols are inscribed to distinguish them, as in the following 

 examples, with their relative weights. 



Name. Atom. Weight of atom. 



Oxygen. . (g) . . 100 



Hydrogen . . . (g) . . 12.5 



Nitrogen. . (g) )77 



Carbon. (g) 76.4 



Sulphur . . . (g) . . 201 

 Lead. .-, 1294.5 



Chemical combination takes place between the atoms of 

 bodies, which then come into juxta-position ; and in decompo- 

 sition the simple atoms separate again from each other, in pos- 

 session of their original properties. The atom or integrant 

 particle of a compound body is an aggregration of simple atoms, 

 and must therefore have a weight equal to the sum of their 

 weights, as will be obvious from the exhibition of the atomic 

 constitution of a few compounds. 



Atom. Weight. 



Water (oxide of hydrogen) (HXg) 12.5 +100= 112.5 



Protoxide of nitrogen. . @ 17? +100= 277 



Deutoxide of nitrogen. . @(o) 177 +200= 377 



Sulphuric acid. . . @@@@ 201 +300= 501 



Oxide of lead. . @@ 1294.5 + 100=1394.5 



Sulphate of lead. . f ()_! 1394.5 + 500=1895.5 



It is unnecessary to make any assumption as to the nature, 



