Royal Society. 61 



angle two right angles. We then see that the object of Theorem I. 

 is to prove that the halves of straight angles are equal, i. e. it is a 

 particular case of Axiom 5. Mr. Wilson might just as well have a 

 theorem to prove that the halves of equal straight lines must be 

 equal. The object of Theorem II. is to prove that if a straight line 

 divides a straight angle into two parts, the two parts are together 

 equal to a straight angle. With regard to Theorem III., we remark 

 that a straight angle is that "made by a straight line with its con- 

 tinuation ; " so that the point to be proved is that a straight line and 

 its continuation are in one straight line. In short, from Mr. Wil- 

 son's point of view, these " Theorems " are not theorems at all ; and 

 he has failed to see it. 



X. Proceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from vol. xlvi. p. 410.] 



April 3, 1873.— William Sharpey, M.D., Vice-President, in 

 the Chair. 



THE following communication was read : — 

 " On an Air-Battery." By J. H. Gladstone, Ph.D., F.B.S., 

 and Alfred Tribe, F.C.S. 



The galvanic battery which we are about to describe is founded 

 on a reaction that we brought under the notice of the Royal 

 Society last spring*. We then showed that if pieces of copper 

 and silver in contact are immersed in a solution of nitrate of 

 copper in the presence of oxygen, a decomposition of the salt 

 ensues, with the formation of cuprous oxide on the silver and a 

 corresponding solution of the copper, while a galvanic current 

 passes through the liquid from copper to silver. We stated, more- 

 over, that this was no isolated phenomenon, but only one of a 

 large class of similar reactions. It seemed desirable to examine 

 more fully the history and the capabilities of the electrical power 

 thus produced. 



It was previously ascertained that the combination of the oxygen 

 takes place only in the neighbourhood of the silver ; and the fol- 

 lowing f ormulae may serve to render the chemical change and trans- 

 ference more intelligible : — 



Before contact, 



m Ag + O + Cu2N0 3 + 0u2NO 8 + nCu ; 

 after contact, 



mAg -f- Cu 2 + Cu2JNr0 3 + Cu2N0 3 + (n-2) Cu. 



This action is evidently a continuous one until either the oxygen 

 or the copper fails. 



Now the oxygen of the atmosphere is practically unlimited in 



* Proc. Eoy. Soc, April 1872, vol. xx. p. 290. 



