336 Remarks on Chemical Theory y and on 



memorandum, printed in connexion with the article fluoric 

 acid or better perhaps in a general appendix, containing sim- 

 ilar things. The same is probably the fact with some other 

 principles, both elementary and proximate, and it would, 

 we imagine, conduce to the progress of the science, and to 

 the comfort and advancement of learners, if newly discov- 

 ered things, when their character is dubious, were kept long- 

 er in waiting at the door, until their title to admission and 

 their proper place were very clearly made out. In chemis- 

 try, as in other branches of knowledge, we are too apt to 

 proceed upon the presumption, that we know every thing, 

 and we construct our arrangements accordingly; but, our 

 errors it is probable, are not few, and our deficiencies, must 

 without doubt, be very numerous. The unexpected dis- 

 covery of some new and important principle, frequently 

 produces a very extensive influence on the relations of other 

 bodies, and of course on the state of the science. How 

 great was the change produced by the discovery of oxigen, 

 and of the constitution of water, and of the atmosphere, 

 and how ramified and important, are the relations which the 

 new views of chlorine introduced into almost every part 

 of the science of chemistry. The subject of chlorine is 

 one respecting which, we may perhaps differ from most of 

 those whose opinions we respect. 



In the first place, we are far from thinking that it is expe- 

 dient, to introduce this difficult and complicated subject, in- 

 to the early part of a course of lectures or of a treatise. It 

 is impossible, either upon the old or new theory, to examine, 

 with success, the numerous and important facts in which chlo- 

 rine acts a part, without an acquaintance with a large number 

 of bodies and without a considerable famiharity with chemical 

 phenomena and reasoning. We are aware that if it be, as 

 many chemists suppose, a distinct principle of combustion, 

 analogy would lead us to place it where Dr. Thomson, Dr. 

 Gorham and others have done — that is, next to oxigen ; 

 but if it be really a distinct principle of combustion, it nev- 

 er comes within the experience of mankind in any common 

 case, nor in any case, except in philosophical or manufacturing 

 experiments. The discussion ofany part of its properties, and 

 even the mention of its name, may therefore be omitted, with- 

 out the slightest inconvenience, till we have gone on so far in 

 thesubjectas to have ititroduced, in a natural and famiharway, 



