282 Royal Society : — 



Our experiments point out, moreover, the universal occurrence, 

 and the general mode of formation of these substances. All organic 

 molecules, particularly in the nascent state, appear to be capable of 

 assimilating the elements of either two or four equivalents of anhy- 

 drous acid. 



The formation of the two groups of acids which are thus produced 

 presents a great analogy with the production of the nitro-substitutes 

 generated under the influence of nitric acid. All these compounds 

 are generated with the elimination of water. In the action of nitric 

 and sulphuric acid upon benzole, for instance, we have, 



CiaHg + HNO,; =Ci2H5N04 +2H0 



Benzole. Nitrobenzole. 



Ci2Hfi + 2HNOfi =Ci2H4N2 0g + 4HO 



Benzole. Dinitrobeuzole. 



C,2H6 + H2S20, =C,2H«S20, +2H0 



Benzole. Sulphobeuzolic 



acid. 



Ci2 He-I- 2H2 S2 Og=Ci2 He S4 O12+4HO 



Benzole. Disulphoben- 



zolic acid. 



The analogy of these reactions is obvious. 



The action of nitric acid upon organic bodies is by no means 

 limited to the production of nitro-compounds corresponding to 

 nitrobenzole and dinitrobeuzole ; frequently additional substitutes are 

 formed ■nith elimination of six, eight, and in a few isolated cases, 

 even of ten equivalents of water. It is possible that analogous 

 sulpho^compounds may exist. Hitherto, however, no substances 

 have been observed in which the assimilation of sulphuric acid has 

 gone further than in the disulpho-acids. 



June 19. — The Lord Wrottesley, President, in the Chair. 



The following communications were read : — 



"On Colour-blindness." By Wilham Pole, Esq., f.R.A.S., 

 F.G.S., Memb. Inst. C.E. 



The author's object in this paper is to state his own case of colour- 

 blindness, which he believes to be one of the most decided on record ; 

 to compare it with others of the same kind ; and to show that the 

 general phenomena attending this defect of vision are more uniform 

 and consistent, as well as more easy of explanation, than is generally 

 supposed. 



For general information on the subject, reference is made to a 

 work lately published by Dr. Wilson of Edinburgh, entitled " Re- 

 searches on Colour-Blinduess," in which a great number of cases are 

 fully described, and the optical and physiological theories of the 

 defect carefully discussed. 



After stating reasons which justify a colour-blind person under- 

 taking the investigation and description of his own case, the author 



