552 Royal Socictij. 



Mef/ahsaHiiis, Pksiosaurus, and several species ol' Steneosaurns, 

 Plerodavti/lus, and Cheloiiia, as also one or more species ol" a bird 

 allied to the Heron. All these specimens are now deposited in the 

 British Museum. 



A paper was also read, entitled, " On a Theorem of Fermat." 

 By Sir John William Lubbock, Bart., V.P., and Treas. R.IS. 



March 4. — A paper was read, entitled, "Miscellaneous Observa- 

 tions on the Torpedo." By John Davy, M.D., F.ll.S. 



The experiments described in this paper were made on a single 

 fish, of middle size, recently taken out of the water. Portions of 

 the electrical organs, cut transversely in thin slices, exhibited under 

 the microscope many elliptical particles, apparently blood-cor- 

 puscles, the long diameter of which was about l-80Uth, and the 

 short about 1 -1000th of an inch, and a few filaments, apparently 

 nervous, irregularly scattered ; some of them tortuous, and all about 

 the 2000th of an inch in diameter. The latter bore no resemblance 

 to muscular fibres. The blood contained some globular particles, 

 having a diameter of the 4000th of an inch, mixed with the elliptical. 

 The mucus for lubricating the surface was found to contain globules 

 apparently homogeneous in substance, but of irregular outline, and 

 in size varying from the 2000th to the 270th of an inch. 



A paper w'as also read, entitled, " On a remarkable property of 

 the Diamond." By Sir David Brewster, K.H., D.C.L., F.R.S.L., 

 V.P.R.S. Ed. 



On re-examining the phsenomena of parallel bauds of light 

 and shade exhibited by reflexion at the plane surface of a diamond, 

 which the author had noticed some years ago, he concludes that 

 they result from the reflexions of the edges of veins or laminae, of 

 which the visible terminations are inclined at different angles, not 

 exceeding two or three seconds, to the general surface. He gives 

 an account of several analogous facts observable in other crystals, 

 more especially those of carbonate of lime, artificially polished in 

 surfaces inclined to the natural j)lanes of cleavage. 



March 1 1 . — The following papers w-ere read : 



1 . " On a Cycle of Eighteen Years in the Mean Annual Height of 

 the Barometer in the Climate of London ; and on a Constant Varia- 

 tion of the Barometrical Mean, according to the Moon's Declina- 

 tion." By Luke Howard, Esq., F.R.S. 



For obtaining the general results communicated in the present 

 paper, the author has followed the same method as that he had 

 adopted in the two former papers laid before the Society on the con- 

 nexion of the barometrical variation with the lunar phases and apsides. 

 Tables are given of the barometrical averages on successive solar 

 years, from 1815 to 1832, so constructed as to exhibit the variation 

 of the moon's influence according to her declination ; and also of 

 these averages on successive cycles of nine solar years, classed 

 according to the moon's place in declination, on either side of the 

 equator. The results deduced from these comparisons are, first, 

 that the barometrical mean in this climate is depressed b)'^ the moon's 

 declination being to the south of the equator; and, secondly, that 

 this depression takes place gradually, commencing with the moon's 



