193 



view, namely to determine the influence of Table Mountain on the 

 direction of the plumb-line. He next relates his jDrogress to Klyp 

 Fonteyn, where he arrived on the 24'th of March, 1838, and describes 

 the operations resorted to for erecting the sector at that place. 

 He then enters into the details of observations made at different sta- 

 tions, and especially with comparative observations at the summit 

 and foot of the mountain of Pequet Berg. The instrument was 

 lastly conveyed back to Cape Town, and again examined, and the ob- 

 servations made with it repeated. The reduction of the observations 

 occupies the remainder of the paper ; and in conclusion, the author 

 remarks, that although these labours have not altogether cleared up 

 the anomaly of La Caille's arc, yet they show that great credit is 

 due to that distinguished astronomer, who with imperfect means, 

 and at the period in which he lived, arrived at a result, derived 

 from sixteen stars, almost identical with that from 1139 observations 

 on forty stars, made with a celebrated and powerful instrument. 



December 19, 1839. 

 MAJOR SABINE, R.A., V.P., in the Chair. 



Henry Drummond, Esq., was duly elected a Fellow of the So- 

 ciety. 



A paper was read, entitled, " An account of experiments made 

 with the view of ascertaining the possibility of obtaining a spark 

 before the circuit of the Voltaic Battery is completed," By J. P. 

 Gassiot, Esq. 



The author of this paper adverts to the fact, of a spark invariably 

 appearing when the circuit of the Voltaic Battery is completed ; an 

 effect which Dr. Faraday has shown can be easily produced, even 

 with a single series. He then refers to the experiments of Mr. 

 Children, Sir Humphry Davy, and Professor Daniell, recorded in 

 the Philosophical Transactions ; in which experiments, when more 

 powerful and extended series were used, the spark was obtained be- 

 fore contact took place. 



In order to ascertain, not only the fact of a spark being obtained, 

 but also the distance through which it may be passed, the author 

 had an instrument jDrepared, which he denominates a Micrometer 

 Electrometer^ and by which an appreciable space of one five-thou- 

 sandth of an inch could be measured with great accuracy. He de- 

 scribes this instrument ; and relates several experiments which he 

 made with a view to test the correctness of its action. He first 

 prepared 160, and then 320 series of the constant battery, in half- 

 pint porcelain cells, excited Avith solutions of sulphate of copper and 

 muriate of soda; but although the effects, after the contact had 

 been completed, were exceedingly brilliant, not the slightest spark 

 could be obtained. He was equally unsuccessful with a water bat- 

 tery of 150 series, each series being placed in a quart glass vessel ; 



