134 Dr. A. C. Brown on Sir Benjamin Brodie's 



Having now seen in what the two systems agree (or may by 

 a very slight accommodation of terminology be made to agree) and 

 in what they differ, we are in a position to estimate their rela- 

 tive advantages. We have seen that they are equally consistent 

 when properly used, and equally capable of mathematical treat- 

 ment (for the first six sections of the calculus can be applied 

 to either). It is true that our system has an atomic origin and 

 retains traces of this in its terminology ; but it may be used, and 

 has often been used, without any reference to any physical theory 

 of matter, just as Sir Benjamin's system might have an atomic 

 theory tacked on to it. 



In comparing the two systems of notation I shall examine (1) 

 the reasonableness of the fundamental hypotheses; (2) the 

 amount of change of formulae which would be involved in a 

 change of the fundamental hypothesis; and (3) the convenience 

 of the formulae themselves. While greatly admiring the ele- 

 gance, simplicity, and consistency of Sir Benjamin's system, I 

 feel compelled to decide against it on all these points. 



1. The fundamental hypothesis of the ordinary system is 

 merely the statement of an experimental fact, namely, that we 

 have not as yet been able to prove that any of the so-called ele- 

 ments contains a component common to it and to any other ele- 

 ment. While this is no doubt a negative conclusion expressing 

 merely our ignorance, it is surely better in the meantime to 

 frame our notation consistently with it than to start from an 

 assumption so purely arbitrary as that the unit of hydrogen is 

 indivisible. Had we no choice but to select one element, and, 

 without considering consequences, fix its symbol, the author's 

 assumption would probably commend itself to us as the most 

 convenient; but we have seen that we are not tied down to such 

 a selection. 



2. Should it be hereafter proved that some of the elements do 

 contain common parts, the change in the case of the ordinary 

 notation would be a simple one. If, for instance, it were proved, 

 as many chemists have supposed, and as Sir Benjamin's brilliant 

 researches on the organic peroxides have rendered it not unrea- 

 sonable to suppose, that chlorine is the peroxide of murium, CI 

 would merely become MuO, and from being an atom would be- 

 come a compound radical ; and just as we now often write Me 

 for CH 3 , or Bz for C 7 H 5 0, so we should, no doubt, often use 

 CI instead of MuO. In the same way, if chlorine were shown to 

 contain hydrogen and to be analogous in composition, as it cer- 

 tainly is in some of its chemical relations, to the peroxide of hy- 

 drogen, we could express this relation by writing C1 = HX, and 

 HC1 = H 2 X, and we should then have on a basis of fact the two 

 analogous series H 2 , H 2 X, H 2 X 2 (hydrogen, hydrochloric acid, 



