Vol. 58.] OF THE PLEISTOCENE EPOCH. 45 
according as the gradient became more or less steeply inclined ; an 
increase of the gradient would bring the mean path of cyclones over 
a line extending from the English Channel to the Kara Sea, and as 
one result of this an excessive precipitation of snow would take 
place on the eastern side of Scandinavia. Both the Author and 
Mr. Dickson seemed inclined to look for the cause of the change of 
gradient in variations of the obliquity of the ecliptic, or in the 
composition of the atmosphere. The speaker was inclined to think 
that a change in the rate of solar radiation might indirectly 
affect the gradient. The methods of Buchan were, by themselves, 
inadequate for a complete discussion of the subject, and the general 
circulation of the atmosphere, concerning which we are now be- 
ginning to attain a clearer understanding, must be taken into 
account, as it had been by Mr. Dickson and the Author. The 
co-operation of geologists in the Northern and Southern Hemispheres, 
and of meteorologists and geologists, was already leading to unex- 
pected progress, and it might be hoped that we were now on the eve 
of important discoveries. 
Mr. A. E. Satrer said that he had come to the conclusion, from 
his observations in Central-and Eastern England, that the data 
upon which ‘ Ice-Sheets’ and ‘ Interglacial Periods’ were based 
could be better explained in other ways. The phenomena due to. 
earth-movements, and those due to chemical and other denuding 
agents acting upon the calcareous and soft argillaceous strata of the 
Midlands, had not been sufficiently appreciated. The highest point. 
-in Central England (Arbury Hill, above 800 feet O.D.) consisted 
of Lias, and it was reasonable to suppose that when younger forma- 
tions, up to and including the Chalk, covered that area, the ground. 
was sufficiently high to affect the climate very considerably. 
Dr. Dv Ricue Pretier remarked that, while the Author had 
stated the annual rainfall at altitudes of 2000 metres to be 2 metres, 
and in lowlands 0-4 metre, it was a fact that in the Alps, on the 
north side, the rainfall of 2 metres was’the average at much lower 
altitudes, namely, of 1000 metres, and even in the Swiss lowlands 
(Zurich, Bale, etc.) it was 1 metre. On the south side of the Alps 
both averages were even higher. Again, the Author’s statement 
that trees required for their growth a mean temperature of 50° Fahr. 
hardly agreed with experience in the Alps, where, for instance in 
the Engadin, trees existed in lower average temperatures. These 
facts had an important bearing on the conditions under which 
glaciation might take place, and hence the data on which the 
Author based his conclusions might apply to Scandinavia, but they 
could not apply to the Alps. 
