408 On the Aiomic Theory. 
correct analyses: but this theory is now supported hy so great’ 
a number of facts, that there is very little fear of its being er-' 
roneous. Perhzps some exceptions will be found to established: 
rules, but they cannot subvert the great mass of facts which 
serve for its base. The same law of definite proportions extends 
itself also to animal and vegetable substances, as the interesting 
labours of M. Chevreul have reeently shown; and it is very’ 
probable that, in continuing to examine carefully the eombina- 
tions of all bodies, it will be found that they constantly cembine 
agreeably to the same law. , of ts 
Mr. Higgins appears to be the first who has considered come, 
binations under this point of view. Unfortunately, as we have 
already said, his work being little known, his name has never 
been inscribed amongst the number of those who have engaged 
themselves on the subject of combinations in definite propor- 
tions. 
The Atomic Theory is very curious; and although by its na-. 
ture it may be subject to great variations according to the man- 
ner in which we view the composition of bodies, it may be con- 
sidered as very important. 
Here, even Mr. Higgins has proved himself to have conceived 
and developed the base of that theory at a time when chemistry 
was scarcely emerged from a chaotic state, and at the moment 
when the results of Lavoisier had been still contested by so many 
distinguished philosophers, particularly by Mr. Kirwan in Eng- 
land. This is what renders his ideas the more important, al- 
though they may not be so well developed as Mr. Dalton had 
afterwards done*. We should often estimate the importance 
of a discovery less by its absolute value than by the state of the 
science at the moment it was made; and under this point of. 
view, the application which Mr. Higgins made in 1789, of the 
recen’ 
* T beg leave to differ from the learned anthor of this article; for, if he 
more carefully peruses the work of Higgins, he must readily perceive that 
Dalton brought his doctrine forward in a mutilated state ; for he omitte 
what appears to me to be the most important part of Mr. Higgins’s beauti, 
ful doctrine; namely, that of the relative forces of attraction of the ultimate 
particles of bocies to each otter, particularly when they are found to be ca- 
pable of uniting in more proportions than one and one. To make this part 
of the subject intelligible to common readers, it must be stated, that Mr. 
Higgins supposed, like many philosophers who had written before him, that 
the attraction of bedies one to another is mutual; but he also observed that, 
in chemical science, there were impoitant modifications of this law. In- 
stance: An ultimate particle of hydrogen and an ultimate particle of oxygen 
united form an atom of water ;—here the attraction of beth particles is 
mutual; that is, they attract each other with equal force, and the compound 
atom is incapable of uniting to any more of its constituent elementary par- 
ticles, having already arrived at its definite proportions. Again: A particle of 
sulphur unites to a-particle of axygen with a certain force, the compound 
iy 
