1873.] Presents. 253 



obtained by means of an electrometer belonging to Sir "William 

 Thomson, were : — 



Silver and copper with deoxygenized copper nitrate 4 



Ditto „ oxygenized ditto 8 to 11 



Copper and zinc with chloride of zinc 62 



Ditto „ water 68 



Ditto „ Daniell's cell S3 



Chloride of zinc is preferred to the sulphate, as it offers less internal 

 resistance, and a solution of 20 per cent, is recommended as about the 

 best conductor*. A single cell of this description is capable of decom- 

 posing dilute sulphuric or hydrochloric acid, when copper electrodes are 

 employed. The two metals might be arranged as in a Daniell's battery ; 

 the zinc would of course require no amalgamation, and the whole might 

 be left for weeks or months without any attention. The oxide of zinc 

 produced generally falls to the bottom of the vessel, and may be 

 separated whenever it is thought desirable. 



The power is thus obtained at a minimum of expense, for the oxygen 

 which combines with the zinc costs nothing. Such a battery would 

 appear to be specially adapted to cases where the galvanic current has 

 to be frequently broken, as in telegraphy ; for at each period of rest it 

 renews its strength by the absorption or diffusion of more oxygen from 

 the air. 



The Society then adjourned over the Easter Eecess, to Thursday, 

 April 24th. 



Presents received March 6, 1873. 



Transactions. 



Gottingen : — Konigliche Gesellschaft der Wissenschaften. Abhand- 

 lungen. Band XVII. 4to. 1872. Nachrichten aus dem Jahre 

 1872. 8vo. 1872. The Society. 



Kazan : — Imperial University. Izvyestiya i TJchenuiya Zapiski (Intel- 

 ligences or Scientific Notes). 1869, Part 5, 6 ; 1870, Part 1-4 ; 

 1871, Part 1-4. 8vo. 1871-72. The University. 



Middlesborough : — Iron and Steel Institute. Journal. 1872. No. 4. 

 8vo. London. The Institute. 



Observations, Eeports, &c. 



Baltimore : — Peabody Institute. Pifth Annual Heport of the Provost 

 to the Trustees, June 6, 1872. 8vo. The Institute. 



* On the authority of Mr. Herbert MacLeod. 



