Royal Society. 165 



sistances and electro-motive forces in the circuit. The light which 

 these investigations has thrown on the theory of current electricity- 

 is very considerable ; and although the labours of Ohm were, for 

 more than ten years, neglected, (Fechner being the only author who, 

 within that time, admitted and confirmed his views,) within the last 

 five years, Gauss, Lenz, Jacobi, PoggendorfF, Henry, and many 

 other eminent philosophers, have acknowledged the great value of 

 his researches, and their obligations to him in conducting their own 

 investigations. Had the works of Ohm been earlier known, and 

 their value recognised, the industry of experimentalists would have 

 been better rewarded. In this country those who have had most 

 experience in researches in which voltaic agency is concerned, have 

 borne the strongest testimony to the assistance they have derived 

 from this source, and to the invariable accuracy with which the ob- 

 served phsenomena have corresponded with the theory of Ohm. This 

 accordance, it may be observed, is altogether independent of the 

 particular hypothesis which may be adopted as to the origin of elec- 

 tro-motive foi'ce ; and obtains equally, whether that force is regarded 

 as being derived from the contact of dissimilar metals, or as refer- 

 able to chemical agency. 



The Council have awarded one of the Royal Medals for this year, 

 which had been proposed for the subject of Chemistry, to Robert 

 Kane, M.D., M.R.I.A., Professor to the Royal Dublin Society, for 

 his paper " On the Chemical History of Archil and Litmus," pub- 

 lished in the Philosophical Transactions for 1840. 



It has been found that various lichens, which communicate no 

 colour to pure water, strike a fine blue with solution of ammonia. 

 The valuable colouring matters archil, litmus and cudbear, are com- 

 mercial preparations of these lichens. Some progress had already 

 been made in the investigation of their colouring principles by the 

 labours of Robiquet, Heeren, and Dumas ; of which the most im- 

 portant step weis the discovery of Orcine, and also of Orceine, into 

 which the former is converted by ammonia ; but the observations 

 were isolated, and the whole subject was in the greatest obscurity. 

 The present memoir by Dr. Kane records the first attempt to sketch 

 a general history of the class : and, considering the great and pecu- 

 liar diflSculties attending inquiries into organic colouring matters, 

 the attempt may be esteemed eminently successful. It proved an 

 investigation of considerable intricacy and great extent, involving 

 several hundred organic analyses ; and it has been conducted in a 

 manner highly creditable to the autlioi-'s skill as an analyst. The 

 paper contains an account of the discovery of a large number of 

 new compounds, not less than twelve, derived from archil and litmus, 

 together with the more exact discrimination of several others, already 

 known, but imperfectly described. The distinction made of two 

 Orcdnes, wliich have hitlierto Ix'en confounded as one, is a striking 

 result contained in tlie paper : while tlie observations on the action 

 of chlorine and of nascent hydrogen upon several of the bodies 

 d<.'scril)ed, ojien new brandies of infjuiry. 



The objects which tlie autlior had in view in these inquiries were 

 the tiirec following : namely, first, to ascertain the primitive form 



