234 PROCEEDINGS OP THE GEOLOGHCAL SOCIETY. [Feb. 22, 



tions. He also asked whether the Kne representing the change in 

 the direction of the pole formed a reentering curve, and whether 

 the theory would account for the climate of Greenland in Miocene 

 times. He suggested changes in the form of the earth which must 

 have affected the direction of its axis. 



The President remarked upon the diflS.culty that arose from 

 astronomical theories differing so much among themselves. He 

 referred particularly to Adhemar's theory, and remarked that the 

 difficulty connected with it is, that it invokes a recurrent cause, 

 which must produce similar effects every 21,000 years, wbUst there 

 is very little evidence of glacial action during the whole long period 

 of the Tertiary epoch. 



The Author, in reply, stated that he could not go back beyond 

 30,000 years, but that he thought glacial conditions must recur. He 

 had not astronomical data beyond 2500 years ; and these were very 

 vague. The motion would be the same in kind, but uncertain in 

 degree. His theory was based entirely upon observed facts. In 

 laying down the curve, he considered it safe to go as far as the semi- 

 circle, as he had observations covering 40° ; but he could not say 

 whether the curve would be a reentering one, although it showed a 

 tendency that way, and would certainly be very nearly so. With 

 regard to the change of climate of Greenland, as evidenced by its 

 Miocene flora, he was not sufficiently versed in botany to pronounce 

 an opinion. He remarked, in conclusion, that the distance of the 

 earth from the sun did not seem to affect the climate of the Southern 

 Hemisphere, and stated that Venus is at present suffering under a 

 most severe glacial epoch. 



3. On Aliophane and an Allied Mineral found at Northampton. 

 By W. Douglas Herman, Esq., Student of the Royal College of 

 Chemistry. 



(Communicated by W. W. Smyth, Esq., F.E.S., V.P.G.S.) 



The only English localities at which, to my knowledge, allophane 

 has been shown to occur are the chalk-pits at Charlton, near Wool- 

 wich, the Purley downs, near Croydon, and a spot not far from 

 Tavistock, in Devonshire. Dr. Charles Berrill, however, shortly 

 before his death, discovered a mineral much resembling the Charlton 

 allophane in physical properties in a pit opened in the ironstones of 

 the Northampton Sand (beds of Inferior-Oolite age) in the grounds 

 of the Northampton General Lunatic Asylum. It occurs as an amor- 

 phous, translucent, somewhat hard and exceedingly brittle mineral, 

 of a yellowish colour inclining to red, and incrusting the surface of 

 a sandstone rock. 



The following analyses of a specimen of this mineral presented by 

 Mr. Sharp, of Dallington, to the Museum of Practical Geology fully 

 bear out, I think, its claim to be called allophane. I append, for 

 the sake of comparison, Mr. A. B. Northcote's analysis of a charac- 

 teristic sample from Charlton. 



