Cambridge Philosophical Society. 485 



lated to test the most minute amount of electric tension. It con- 

 sists of an electroscope surmounted by a disc A of glass coated 

 with gold and varnished on its upper surface ; the disc B, varnished 

 on both sides, is placed on this ; it has a glass handle ; the disc C 

 has a handle of glass tube so constructed that the handle of B can 

 pass through it. The delicacy of this instrument was shown by the 

 results which followed the touching of the upper disc with an iron 

 wire once, twice, thrice, four, five, and ten times. 



A paper by J. P. Gassiot, Esq., F.R.S. M.E.S. &c, was then 

 read, "On the Polarity of the Voltaic Battery." After alluding to 

 the confused descriptions of voltaic batteries which have emanated 

 from the varied modes of arranging the elements, Mr. Gassiot men- 

 tions that the electric tension of the water battery has been de- 

 scribed as differing from that of other battles ; the end we have 

 been accustomed to regard as positive is designated resinous, and 

 the other vitreous ; and this result presented itself to him in his 

 early experiments; upon closer investigation, however, it appears 

 that these conflicting results are due to want of attention to the 

 mode of manipulating with the electroscope. When the excited rod 

 is applied to the side of this instrument, the leaves are affected in a 

 manner precisely the reverse of what happens when it is applied above. 

 The anomalous results occur in the former case, and are due to the 

 effect of the glass rod on the instrument itself, disturbing not only 

 the natural electricity contained in the leaves, but also the surplus 

 acquired by being in contact with, or charged by, the battery. The 

 charge is driven upwards into the plate, and the leaves approach the 

 normal condition. When the rod is applied above the converse 

 occurs. These experiments were made with a new double electro- 

 scope. In conclusion, the author offers a few remarks on electrical 

 nomenclature, and conceives that so long as we are content to con- 

 tinue the terms positive and negative, vitreous and resinous, in ap- 

 plication to the machine, we should not object to use them in 

 reference to the battery. 



Mr. Walker then concluded the reading of his translation of M. 

 Becquerel's paper " On the Electro-Chemical properties of Gold," in 

 which are given some interesting applications of theory to practice. 

 In extracting ore from a solution of several metals, another solution 

 is made of all the metals but that one ; it is made as nearly as pos- 

 sible of the same specific gravity ; the two form the exciting liquids 

 to a single cell arrangement, and the effect is the release of the metal 

 required. Modifications of the same principle are applied to gild- 

 ing, the author giving the preference to the single cell apparatus. 



Mr. Weekes's Electro- Meteorological Register for October was 

 read. 



CAMBRIDGE PHILOSOPHICAL SOCIETY. 



Nov. 14, 1842. — Professor Fisher read a paper on the Develop- 

 ment of the Spinal or Intervertebral Ganglia, and on various Mal- 

 formations of the Nervous System. This communication was one of 



