404 Prof. Forbes's Reply to Mr. Hopkins 



rated aniline. Its carbon must, therefore, be completely 

 separated. The following formula exhibits this change: — 



2C /"4n + 2CiO - /C„N,N + C,, + 2ClCa + 



V ^ I 



Chloraniline. 

 This decomposition gives the key to some phaenomena of which 

 I have already made mention in the preparation of chlorani* 

 line. 



I mentioned that in the last stage of the distillation, so soon 

 as the mass in the retort commences to become dry, evolution 

 of ammonia takes place, and aniline at the same time distils 

 over. This reaction evidently depends on a transformation 

 similar to that just mentioned. The vapours of the chlori- 

 nated base which deposit on the cooler parts of the apparatus 

 meet with hot potash on the sides of the retort, and are de- 

 composed into aniline, ammonia, and hydrochloric acid. 



By carefully mixing a small portion of very pure chlor- 

 isatine with caustic baryta and slowly heating, a product of 

 distillation was obtained which did not exhibit the slightest 

 alkaline reaction, whilst, in the heated residue, not a trace of 

 chlorine could be detected. All the nitrogen and chlorine of 

 the chlorisatine had consequently distilled over in the form of 

 chloraniline. 



Action of Potassium on Chloraniline. 

 The decomposition experienced by the chlorinated base 

 when its vapour is passed over fused potassium offers no great 

 peculiarity. The potassium becomes incandescent and is con- 

 verted into chloride and cyanide. A large quantity of carbon 

 is also deposited. 



[To be continued.] 



LVII. Reply to Mr. Hopkins on the Motion of Glaciers ; with 

 Reasons for avoiding further controversy. By James D. 

 Forbes, Esq.^ F.R.S.^ Corresponding Member of the Insti- 

 tute, and Professor of Natural Philosophy in the University 

 of Edinburgh *. 



'T'O enter into controversy with Mr. Hopkins would be to 

 -■ analyse all that he has written on the subject of glaciers, 



namely eighty-one octavo pages and thirty-six closely printed 



quarto ones, a majority of which are filled with mathematical 



reasonings intended to bear upon the subject. 



As replies in controversy usually extend beyond the bounds 



of the reasonings replied to, it is easy to see that to do justice 

 • Communicated by the Author. 



