Mr. G. C. Foster on Chemical Nomenclature. 57 



X. The phenomena of magnetic storms indicate the existence 

 of controlling laws analogous to those which regulate the normal 

 fluctuations. See Proceedings of the American Philosophical 

 Society, October 21, 1864. 



The foregoing comparisons have been based on General Sa- 

 bine's discussions of the St. Helena records. It would be desirable, 

 if it were possible, to confirm them by observations at other sta- 

 tions near the equator ; but the need of such confirmation is in 

 great measure obviated by the variety of ways in which I have 

 shown the probable connexion of gravity and magnetism. At 

 extra-tropical stations the rotation tide becomes so prepondera- 

 ting that it is difficult to trace the diminished gravitation- and 

 differential-tides ; still I shall look confidently to a fuller deve- 

 lopment of the theory of tidal action for future additional sup- 

 port to my views. 



IX. On Chemical Nomenclature. By G. C. Foster, B.A., 

 Lecturer on Natural Philosophy in Anderson's University, 

 Glasgow. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, London, June 26, 1865. 



I BEG to offer a few remarks on some observations contained 

 in a paper " On Chemical Nomenclature," by my respected 

 friend and teacher Professor Williamson, published in the June 

 Number of your Magazine (vol. xxix. p. 464). With most of the 

 suggestions contained in this paper, and in the Professor's pre- 

 vious communication to the Chemical Society on the same sub- 

 ject, I have already expressed complete agreement; I will there- 

 fore confine myself here to the only important point on which I 

 have ventured to differ from him. 



This is as to the correct use of the word " acid." Professor 

 Williamson contends for the application of this word to such 

 substances as those represented by the formulae 



S0 3 5 N 2 5 5 (C 2 H 3 0) 2 0, &c, 



and alleges, in words which I have previously quoted (Phil. Mag. 

 S. 4. vol. xxix. p. 262), that this was clearly the original sense of 

 the term. My own impression being that the word acid was 

 long in general use before any meaning was attached to it which 

 it was possible to define with accuracy, I pointed out (loc. cit.) a 

 few facts relating to the former use of this word which seemed 

 to me inconsistent with the statement above alluded to ; and also 

 drew attention to its having been employed even by modern che- 

 mists, down to the time of Gerhardt and Laurent, not only for 

 oxides such as SO 3 , N 2 O 5 , &c v but for hydrogen-salts such as 



