100 THE MEAN EADIAL VARIATION OF THE GLOBE. [May 1895, 



that of the globe an amount of contraction which would require a 

 large amount of flexuring of the crust in order to establish equi- 

 librium. 



The Rev. Edwin Hill said that such a shrinkage would produce 

 no difference of any consequence in gravity or air-pressure. 



The Author, in reply, said that his estimate of a contraction of 

 horizontal extension by folding was on the assumption of a contracting 

 globe causing rock- folding, the assumption which he opposed, and that 

 therefore the remarks of Prof. Hughes were practically in support 

 of his views. Cooling and shrinkage before the Cambrian period, 

 in reply to Prof. Hull, were not denied ; but he thought he had 

 shown that since that epoch no appreciable cooling or shrinkage 

 of the globe had taken place, that therefore the mean radius 

 of the planet had not decreased, and that as a consequence the 

 foldings and plications of the Cambrian and post-Cambrian rocks 

 had not been the result of the secular cooling and consequent con- 

 traction of the globe. 



