Geological Society of London. 185 



Epoch of Geology." By Lieutenant-Colonel Drayson, E.A., F.K. A.S. 



Communicated by Alfred Tylor, Esq., F.G.S. 



In this paper the author started from the fact that the pole of the 

 ecliptic could not be the centre of polar motion, as the pole varied 

 its distance from that centre. He indicated the curve which the 

 pole did trace, and this curve was such as to give for the date 

 13,000 B.C. a climate very cold in winter, and very hot in summer 

 for each hemisphere. The duration of the glacial epoch he fixed at 

 about 16,000 years. The calculations resulting from this movement 

 were stated to agree accurately with observation. 



Discussion.— Professor Eamsay inquired whether the author's theory involved 

 the recurrence of glacial epochs, and whether he considered the course of phenomena 

 to be constant in early astronomical epochs. ■ ♦ 



Eev. Osmond Fisher inquired whether the theory was founded on observed facts,_ or 

 whether it was a purely physical theory. He also asked whether the line representing 

 the change in the direction of the pole formed a re-entering 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 difficulty that arose from astronomical theories 

 differing so much among themselves. He referred particularly to Adhemar's theory, 

 and remarked that the diflSculty connected with it is, that it invokes a recurrent 

 cause, which must produce similar effects every 21,000 years, whilst 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 semicircle, as he had observa- 

 tions covering 40° ; but he could not say whether the curve would be a re-entering 

 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 pronoimce an opinion. _ He remarked, 

 in conclusion, that the distance of a planetary body from the sun did not seem to 

 affect climate, and stated that Yenus is at present suffering under a most severe glacial 

 epoch. 



3. " On Allophane and an allied Mineral found at Northampton." 

 By W. D. Herman, Esq. Communicated by Warington W. Smyth, 

 Esq., F.E.S., F.G.S. 



In this paper the author gave analyses of an amorphous, trans- 

 lucent, reddish-yellow mineral, foimd incrusting sandstone in the 

 Ironstones of the Northampton sands, the comparison of which with 

 Mr. Northcote's analysis of allophane from Charlton leads him to 

 infer the identity of the two minerals. He also noticed a soft white 

 substance found in certain joints of a section of the Northampton 

 sand, likewise referred to allophane by the late Dr. Berrell, who 

 analyzed it. This substance was said to occur not unfrequently in 

 the inferior Oolite of the Midland Counties. By analysis, it was 

 shown to agree nearly with Samoite and Halloysite. 



Discussion. — Mr. David Forbes stated that he had found phosphoric acid in the 

 first-mentioned mineral, which was perhaps the cause of its lustre. The mineral was 

 probably not pui'e allophane. 



Professor Morris suggested a chemical and microsocopical examination of the strata 

 above the places in which these minerals occur, which would probably reveal the con- 

 ditions under which they have been formed. They were probably produced by the 

 decomposition of silicates in the overlying rocks during the percolation of water. 

 This applied also to the Charlton locality. 



