Royal Society. 449 



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

 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 j 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. ['rout'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. — A paper was read, entitled, " Observations of the Comet 

 of Encke, made in June 1832." By Thomas Henderson, Esq., His 

 Majesty's Astronomer at the Cape ot Good Hope. Communicated, 

 by Command of the Lords Commissioners of the Admiralty, by Cap- 

 tain Beaufort, 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 35 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- 

 tions, a transit instrument by Dollond was used, which was 10 feet 

 in focal length, and 4*75 inches aperture. For observing the comet, 

 an eye-glass magnifying 86 times was employed. 



A paper was then read, entitled, "On the supposed Powers of Suc- 

 tion of the Common Leech." By Thomas Andrew Knight, Esq., 

 F.R.S., President of the Horticultural Society. 



From observing the feebleness of the muscular force exhibited by 

 the leech in its progressive movements through the water, the author 

 was led to doubt its possessing the powers of suction that are so uni- 

 versally ascribed to it. A fact which came under his notice above 

 sixty years ago, of considerable loss of blood from the leg following 

 the bite of a vigorous leech, suggested to him the idea that the animal 

 might become filled with blood simply by the injection of its body, in 

 consequence of the impetus with which the blood is made to flow into 

 it from the part bitten ; — an impetus which he imagines may be oc- 

 casioned by the introduction of a peculiar kind o( venom. He con- 

 siders the irritation which often accompanies the bite of a leech as 

 corroborating this hypothesis : he admits, however, that the inflam- 

 mation excited by the sting of a bee or a wasp is attended with effects 

 of a totally opposite kind ; for, in that case, the blood, instead of 

 having a tendency to flow, stagnates around the point where the 

 poison has been instilled. 



A paper was also read, entitled, " Experimental Researches in 

 Electricitv.— Fourth Series." Bv Michael Faradav, Esq., D.C.L., 



Third Series. Vol. 3. No. 18. Dec. 1833. '6 M 



* 



