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 Society.
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 ;
