436 Royal Society. 



it is the degree of La Caille at the Cape of Good Hope, in 

 latitude 33° 18'; but this is so disproportionately great, that no 

 use can be made of it. 



May 12, 1828. J. Ivory. 



LXVI. On the characteristic Equation of Curve-surfaces 

 capable of being evolved in a Plane. By M. Fayolle. 



To the Editors of the Philosophical Magazine and Annals. 

 Messieurs, 

 /^E n'est pas sans surprise que j'ai lu, dans votre dernier 

 V^ N°; du Philosophical Magazine, le passage suivant, p. 334 : 



d*x d*x / d* z \ 3 _ 



dx 2 ' dy 1 V dxdy J 



" an equation which, indeed, has long been known, but in the 

 opinion of Mr. Gauss has never yet been rigorously demon- 

 strated." 



Les geometres savent que Monge et Meusnier ont donne 

 des demonstrations rigoureuses de cette equation differentielle 

 partielle du second ordre, qui appartient aux surfaces develop- 

 pables. Pour s'en assurer, je renvoie vos lecteurs aux volumes 

 9 et 1 de la collection des Memoir es des Savans etrangers. 



Ce 15 Mai, 1828. Fayolle, 



Ancien chef d' etude a lecole Polytechnique. 



LXVI I. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Being enabled to resume our regular reports of the proceedings of 

 this Society, we commence at present with a list of the papers 

 read before the Society during the present session, which have 

 not hitherto been noticed in the Philosophical Magazine.] 



Dec. 20, 1827.— OESE ARCHES to discover the faculties of 

 -i-V pulmonary absorption with respect to char- 

 coal. By G. Pearson, M.D. F.R.S. — A Catalogue of nebulae and 

 clusters of stars in the southern hemisphere, observed at Paramatta 

 in New South Wales. By James Dunlop, Esq. in a letter addressed 

 to Sir Thomas M. Brisbane, Bart. Communicated by Mr. Herschel. 



Jan. 10, 1828. — On the life of plants and animals. By Sir G. 

 Gibbs, M.D. F.R.S. — Observations on the comparative magnetic 

 intensity shown by a horizontal needle at the bottom and on the 

 tops of mountains at Port Bowen and Spitzbergen. By Captain 

 Henry Foster, R.N. F.R.S. 



17. — On Capt. Parry's and Lieut. Foster's experiments on the 

 velocity of sounds. By Dr. G. Moll, Professor of Natural Philoso- 

 phy in the University of Utrecht. Communicated by Capt. Henry 

 Kater, V.P.R.S. — An account of a series of experiments, made 



with 



