302 Royal Astronomical Society. 



Received April 12, 1844. 



Note. — I have recently constructed an instrument, by means 

 of which the tension in a single series of the voltaic battery 

 can vi'ith facility be tested without the aid of Zamboni's pile. 

 Fig. 8 represents the electroscope, in the construction of which 

 I was in a great measure indebted to an apparatus described 

 by Dr. Hare*. A is a glass vessel, y\cp. 8. 



the stem of which is well-coated with 

 lac ; B, B', two copper wires passing 

 through glass tubes and corks; D, 

 D', gilt discs, each about two inches 

 diameter, attached to the wires ; P, 

 a copper plate with a wire passing 

 through a glass tube ; to the end of 

 the vt'ire is attached a narrow strip of 

 gold leaf, L. The discs must be ad- 

 justed with care, so as to allow the 

 leaf to be equidistant from each. If B is connected by a wire 

 attached to the platinum, and B' by another wire attached to 

 the zinc of a single cell of the nitric acid battery, insulated on 

 a plate of lac, and an excited glass rod is approximated very 

 gradually towards the plate P, the gold leaf will be attracted 

 to B', or the disc attached to the zinc ; and if excited resin is 

 approximated in a similar manner, the leaf is then attracted to 

 B, or the disc attached to the platinum. By means of this in- 

 strument, my friend, the Rev. Charles Pritchard, obtained 

 signs of tension in a single cell excited by dilute sulphuric 

 acid with platinum and zinc. This experiment I subsequently 

 verified, and obtained similar results with single cells of other 

 usual arrangements of the voltaic battery ; but in all the ex- 

 periments I made, the higher the chemical affinities of the ele- 

 ments used, the greater was the development of the evidence 

 of tension. 



March 1844. 



XLIX. Proceedings of Learned Societies, 



ROYAL ASTRONOMICAL SOCIETY. 

 [Continued from p. 230.] 

 April 12, nPHE following communications were read; — I. Addi- 

 1844. *■ tional Observations of Faye's Comet, made at the 

 Observatory of Trinity College, Dublin, by Mr. C. Thompson, ac- 

 companied by an explanation of the method of observation and re- 

 duction. Communicated by Sir W. Hamilton. For these we refer 

 to the Monthly Notices, vol. vi. p. 67. 



• Silliman's Journal, vol. xxv. 



