Evans— A Possible Cause of Climatal Changes. 171 



rinthodonts at present known; and an ophiomorplious division, 

 typified by OpMderpeton. The anurous frog-like form will be 

 alone wanting to complete the representation of the existing 

 Amphibia in ancient times. 



In concluding, it is but right that we should return our best 

 thanks to Mr. Brownrigg, Mr. S. Bradley, and Mr. K. Dobbs, not 

 only for what they have done in collecting these remains, but for 

 the generous manner in which they have placed all their collections 

 at our disposal. Our thanks are also due to the Rev. Prof. Haugh- 

 ton, M.D., the Eev, J. Emerson, and Dr. Swan, for the loan of speci- 

 mens ; and to the Du-ectors of the Irish G-reat Southern Eailway for 

 liberty to bring from Carlow any quantity of Coal-fossils, carriage 

 free. 



n. — On a Possible Cause of Climatal Changes.^ 

 By John Evans, F.R.S., F.S.A., Sec. Geol. Soc. 



THE Author called attention to the great climatal changes which 

 have taken place in the northern hemisphere, and suggested 

 that corresponding changes have in all probability taken place in the 

 southern hemisphere ; but on account of our more limited geological 

 observations we are unacquainted with them. 



The extreme refrigeration of this portion of the globe at the glacial 

 period is constantly receiving fresh corroboration, and various 

 theories have been proposed to account for this accession of cold in a 

 satisfactory manner. 



Variations in the distribution of land and water, changes in the 

 direction of the Gulf stream, the greater or less eccentricity of the 

 earth's orbit, the passage of the solar system through a cold region 

 in space, fluctuations in the amount of heat radiated by the sun, 

 alternations of heat and cold in the northern and southern hemi- 

 spheres consequent upon the precession of the equinoies, and even 

 changes in the position of the centre of gravity of the earth, and con- 

 sequent displacement of the polar axis, have all been adduced as 

 causes calculated to produce the effects observed. 



Mr. Evans referred to the observations of Laplace and other 

 astronomers as rendering untenable any theory involving a material 

 change in the earth's axis of rotation. 



Sir Henry James (Athenceum, Aug. 25, 1860) appears nevertheless 

 to have concluded that it was impossible to explain certain geological 

 phenomena without recourse to the supposition of constant changes 

 in the position of the axis of the earth's rotation. The late Sir John 

 Lubbock's observations (Quart. Jour. Geol. Soc, Vol. v., p. 5), were 

 also quoted by the author. 



Sir John Lubbock, in common with other astronomers, appears to 

 have regarded the earth as consisting of a solid nucleus with a body 

 of water distributed over a portion of its surface, and upon this 



1 Abstract of a paper read before the Eoyal Society, March loth, 1866. 



