659 



permanent gas from all liquids, except the metals, when exposed to 

 intense heat. 



December 17, 1846. 

 The MARQUIS OF NORTHAMPTON, President, in the Chair. 



"Researches on Physical Geology." — Parti. The Figure and 

 Primitive Formation of the Earth. By Henry Hennessy, Esq. 

 Communicated by Major North Ludlow Beamish, K.H., F.R.S. 



The author's investigations of the figure of the earth proceed on 

 the hypothesis of its having originally been a heterogeneous fluid 

 mass, possessing only such general properties as those which have 

 been established for fluids ; and independently of the supposition, 

 with which the theory has generally been complicated, that the vo- 

 lume of the entire mass, and the law of the density of the fluid, have 

 suffered no change in consequence of the solidification of a part of 

 that fluid. Assuming the figure of the mass to be an ellipsoid of 

 revolution, the author obtains general analytical expressions for its 

 ellipticity, and for the variation of gravity at its surface. He gives 

 a general sketch of the consequences that may result from the im- 

 proved hypothesis of the primitive figure of the earth, to physical 

 geology, that is, to the changes occurring upon the external crust of 

 the earth during the process of its solidification, resulting both from 

 calorific and chemical changes taking place among its different parts, 

 and giving rise to a process of circulation throughout the fluid por- 

 tions of the inass. 



The present memoir is only the first of a series which the author 

 announces it is his intention to communicate to the Society on the 

 same subject. 



January 7? 1847. 

 The MARQUIS OF NORTHAMPTON, President, in the Chair. 

 Sir George Back, Capt. R.N., was elected into the Society. 

 The following paper was read : — 



" QuelquesRecherches surl'ArcVoltaique; et sur I'influence qu'ex- 

 erce le Magnetisme, soit sur cet Arc, soit sur les Corps qui trans- 

 mettent les Courants Electriques Discontinus." By M. Auguste 

 De la Rive, Foreign Member of the Royal Society, Professor in the 

 Academy of Geneva, Corresponding Member of .the Academy of 

 Sciences of Paris, &c. 



In the first section of this memoir the author gives a detailed de- 

 scription of the phenomena exhibited by the luminous voltaic arc 

 produced either in a vacuum or in atmospheric air, or in hydrogen 

 gas, by employing electrodes of different kinds of conducting sub- 



