355 



feet conductor, such as honey, and which, though it communicated 

 weak shocks, yet did not decompose water. 



The author also ascertained that the electrical shocks of the tor- 

 pedo, even when powerful, produced no sensible effect on an ex- 

 tremely delicate magnetic electrometer. He explains these negative 

 results by supposing that the motion of the electricity in the torpe- 

 dinal organ is in no measurable time, and wants that continuity of 

 current requisite for the production of magnetic effects. 



On a Method of comparing the Light of the Sun with that of the 

 fixed Stars. By William Hyde Wollaston, M.D. F.R.S. Read 

 December 11, 1828. [Phil. Trans. 1829,;?. 19.] 



In the Philosophical Transactions for the year 1767, a suggestion 

 is thrown out by Mr. Michell, that a comparison between the light 

 received from the sun and any of the fixed stars, might furnish data 

 for estimating their relative distances ; but no such direct comparison 

 had been attempted. Dr. Wollaston was led to infer from some ob- 

 servations that he made in the year 1799, that the direct light of the 

 sun is about one million times more intense than that of the full moon, 

 and therefore very many million times greater than that of all the 

 fixed stars taken collectively. In order to compare the light of the 

 sun with that of a star, he took, as an intermediate object of com- 

 parison, the light of a candle reflected from a small bulb, about a 

 quarter of an inch in diameter, filled with quicksilver, and seen, by 

 one eye, through a lens of two inches focus, at the same time that 

 the star or the sun's image, placed at a proper distance, was viewed 

 by the other eye through a telescope. The mean of various trials 

 seemed to show that the light of Sinus is equal to that of the sun 

 seen in a glass bulb one tenth of an inch in diameter, at the distance 

 of 2 10 feet, or that they are in the proportion of one to ten thousand 

 millions ; but as nearly one half of the light is lost by reflection, the 

 real proportion between the light from Sirius and the sun is not 

 greater than that of one to twenty thousand millions. If the annual 

 parallax of Sirius be half a second, corresponding to a distance of 

 525,481 times that of the sun from the earth, its diameter would be 

 3'7 times that of the sun, and its light 13' 8 tunes as great. The di- 

 stance at which the sun would require to be viewed, so that its 

 brightness might be only equal to that of Sirius, would be 141,421 

 times its present distance ; and if still in the ecliptic, its annual pa- 

 rallax in longitude would be nearly 3" ; but if situated at the same 

 angular distance from, the ecliptic as Sirius is, it would have an an- 

 nual parallax, in latitude, of 1"'8. 



On the Water of the Mediterranean. By William Hyde Wollaston, 

 M.D. F.R.S. Read December 18, 1828. [Phil. Trans. 1828, p. 29.] 



The late Dr. Marcet hi his examination of sea- water, of which he 

 has given an account in the Philosophical Transactions for 1819, had 



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