Geological Society. 67 



a striking series of geological facts which demonstrate the much 

 greater age of the solar system. A quarter of a century ago Dr. 

 Croll first pointed out the important evidence afforded by sub-aerial 

 denudation as to the antiquity of the Earth. By that scale and by 

 other concurrent sources of testimony he concludes that the Earth 

 must have existed in a condition not greatly different from what 

 now prevails for at least seventy millions of years. That being so, 

 we are bound to seek a source of vastly greater heat than can be 

 derived from simple shrinkage of a nebula. Such a source Dr. Crotl 

 finds in his "Impact " theory of: solar genesis, and he supports his 

 theory by many ingenious arguments. Sir William Thomson 

 regards it as enormously less probable than the gravitation theory, 

 on account of the necessary assumption of exact aiming of the col- 

 liding bodies ; but the probability of the collision of dark masses is 

 a question of their numbers, distribution, and of time; and against 

 the gravitation theory there is the fact that the actual motion 

 observable in many stars cannot have been derived from that source. 

 Further, it may be said that the "Impact" theory appears to get 

 remarkable support from the recent important researches of Dr. 

 Huggins regarding the constitution of nebulae, the results of which 

 he communicated to the Royal Society during the past session. 



Cosmic Evolution, being Speculations on the Origin of our Environ- 

 ment. By E. A. Eidsdale. London : Lewis. 

 Mb. Eidsdale, in his essay, assumes that the universe in its pri- 

 mordial condition consisted of a uniform gaseous expansion 

 possessed of an inconceivably high temperature. Chemical com- 

 bination became possible only as temperature of this attenuated 

 matter decreased; and with each successive combination there was, 

 in accordance with well-known laws, a shrinkage in volume. 

 Chemical activity was at first violently energetic ; but as inorganic 

 evolution proceeded, elements differentiated and compounds in- 

 creased, more stable conditions arose, and the chemically inert 

 survived to form a basis favourable for the production and main- 

 tenance of life and organic compounds. JVIr. Eidsdale develops 

 his thesis in a rather inconsequent manner; and although in their 

 general bearings his speculations may be accepted as satisfactory, 

 he trenches on subjects which are too profound and vast to be fairly 

 within the grasp of his limited knowledge and experience. 



IX. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxvii. p. 435.] 



April 17, 1889.— W. T. Blanford, LL.D., F.E.S., President, 



in the Chair. 



f T^HE following communications were read : — 



-*- 1. " On the Production of Secondary Minerals at Shear-zones in 



the Crystalline Eocks of the ]\Ialvern Hills." By Charles Callawav, 



Esq., M.A., D.Sc, E.G.S. 



In a previous communication the author had contended that 



