197 



lie finds the sulphate to consist of 73*575 of protoxide of lead, and 

 26*425 of sulphuric acid; and that the former contains 5-274 of 

 oxygen. According to these results, the equivalent number for lead 

 is 103-6. 



By experiments with the chloride of lead, which gave very uniform 

 results, Dr. Turner obtained an equivalent number for chlorine, closely 

 agreeing with that calculated from the analysis of chlorate of potash 

 in the experiments of Berzelius, namely, 35*45, but totally incon- 

 sistent with the atomic weight assigned to it by British chemists. The 

 accuracy of this result was further confirmed by a careful comparative 

 analysis of the binoxide and bichloride of mercury. 



The author next endeavoured to determine the equivalent number 

 for silver, by the analysis of its oxide and sulphuret, but could not 

 arrive at any precision in his results. The equivalent number for 

 barium may be calculated from his analysis of the chloride already 

 published in the paper before alluded to. His investigation of the 

 equivalent of nitrogen was attempted by means of the analysis of the 

 nitrates of silver, of lead, and of baryta ; the mean result of which 

 gives 14*15, agreeing very nearly with that assigned by Berzelius. 

 His investigation of the atomic weight of sulphur is not yet com- 

 pleted • but he details several previous steps in this inquiry, which he 

 intends to prosecute on a future occasion. He estimates the equiva- 

 lent of mercury at 202 • a number which he considers as a close ap- 

 proximation. 



He concludes by various remarks on the inconsistency with expe- 

 riment, which is apparent in many of the numbers adopted as chemical 

 equivalents by British chemists; and on the inaccuracy of those num- 

 bers which have been employed as elements in calculating the equi« 

 valents of nearly all the other elementary substances. The author 

 thinks that Dr. Prout's hypothesis, as advocated by Dr. Thomson, that 

 all atomic weights are simple multiples of that of hydrogen, can no 

 longer be maintained, and that it is at variance with the most exact 

 analytical researches. 



May 23, 1833. 



HIS ROYAL 'HIGHNESS THE DUKE OF SUSSEX, K.G., 

 President, in the Chair. 



A paper was read, entitled, ee Observations of the Comet of Encke, 

 made in June 1832." By Thomas Henderson, Esq., His Majesty's 

 Astronomer at the Cape of Good Hope. Communicated, by Com- 

 mand of the Lords Commissioners of the Admiralty, by Captain Beau- 

 fort, R.N., F.R.S., Hydrographer to the Admiralty. 



Most of the observations recorded in this paper were made by a 

 circular micrometer constructed by Simms, and applied to an achro- 

 .matic telescope of Dollond's, 45 inches in focal length, and 3*5 inches 

 aperture, furnished with a portable equatorial stand, capable of being 

 adjusted to any latitude. The magnifying power was about 30, and 

 the radius of the ring was an arc of 1015 seconds. In other observa- 



