412 Geological Society. 



estimated the quantity of effect by his volta-electrometer, and then 

 estimated the quantity of zinc in the battery employed in producing 

 the effect by the results of an analysis of a given portion of the ex- 

 hausted charge. In this way it was easy to tell how much zinc was 

 dissolved from any one plate, or from all the plates, and to compare 

 it with the quantity of water decomposed in the volta-electrometer. 

 Thus, with a perfect battery of 40 pairs of plates, an equivalent of 

 water decomposed in the volta-electrometer would be the result of 

 the solution of an equivalent of zinc from each zinc plate, or forty 

 equivalents in the whole ; but with a battery not so perfect, a greater 

 proportion of zinc would be dissolved by the acid in the cells. 



When the new battery was thus compared with that of the ordi- 

 nary form, it was found to have greatly the advantage. Thus, with 

 40 pairs of plates, the former lost 2*21 equivalents at each plate, 

 and the latter 3\54. With 20 pairs of plates, the former lost 37 per 

 plate, and the latter 5-5. With 10 pairs of plates, the former lost 

 6'76 per plate, and the latter 15*5. The author refers to two diffi- 

 culties still existing in the construction of the battery, but considers 

 its value so great as to deserve receiving that degree of attention 

 by the application of which these difficulties may be removed. 



The author then investigated many other practical points in the 

 use of the battery, ascertaining the influence of various circumstances 

 in the manner already described. Thus he found nitric acid to give a 

 higher result of voltaic action than sulphuric or muriatic acid; the 

 quantity of zinc dissolved in order to produce decomposition of an 

 equivalent of water being only 185 per plate when nitric acid was 

 used, 3'8 when muriatic acid was used, and 4'66 when sulphuric acid 

 was employed. The acid which he afterwards used as the best for 

 ordinary purposes consisted of 200 water, 4 # 5 oil of vitriol, and 4 

 nitric acid. 



The mode of proof adopted by the author was of course independ- 

 ent of the strength of the acid; as was shown by making experi- 

 ments with the same acid at very different strengths; thus, when 

 nitric acid was used, and tbe strengths were as 1,2, and 4, the pro- 

 portion of zinc dissolved was very nearly the same for the water de- 

 composed. The same result was obtained when sulphuric acid was 

 employed. 



The different circumstances of uniformity of charge — purity of zinc 

 —foulness of the zinc plates — new and old plates — vicinity of the 

 copper and zinc — doubling of the copper — first immersion of the 

 plates — number of plates — size of the plates and simultaneous de- 

 compositions — were then considered, and such of them as would ad- 

 mit of experimental comparison in the manner already described 

 were put to this test. 



GEOLOGICAL SOCIETY. 



May 13th. — A paper was first read, " On the Cretaceous and Ter- 

 tiary Strata of the Danish Islands of Seeland and Moen j" by Charles 

 Lyell, Esq., P.G.S. 



The author commences with a short account of the succession of 



