David Milne-Home on Ancient Glaciers. 59 
This conclusion is also arrived at by comparing the mean 
annual temperature of Geneva with that of the localities where 
the glaciers now melt. Thus (as has been shown by Princi- 
pal Forbes) the mean annual temperature of the Arveiron, 
where the Mer de Glace terminates, is 383° Fahr., whilst 
that of Geneva is 48°, being a difference of about 10°; and 
assuming the usual rate of 1° Fahr. for every 300 feet, these 
10° correspond roughly to a height of 3000 feet. 
I am quite aware that the view which I have adopted, of 
supposing this part of Europe to have stood 3000 feet higher 
above the sea than at present, is rejected by De Charpentier, 
who, I believe, is the latest Swiss geologist who has gone 
deeply into this subject ; and it seems rather presumptuous to 
offer an opinion at variance with so great an authority. His 
way of accounting for the lower temperature necessary for the 
production of extended glaciers is by supposing (I quote his 
words) ‘‘a long series of seasons, similar to the rainy and 
cold seasons which succeeded one another from the year 1812 to 
1818” (Charpentier “‘ Sur les Glaciers,” p. 319). And he adds, 
that a very long continuance of such ungenial seasons should 
be no objection, considering that in the explanation of any 
geological phenomenon, it is allowable to assume as much time 
as may be necessary. I confess, however, that the reason 
thus assigned by De Charpentier for his theory is not satis- 
factory to my mind; for during the cold and rainy years re- 
ferred to none of the alpine glaciers extended more than a 
few hundred feet beyond their usual limits; and therefore, 
to cause a glacier to grow to the length of 80 to 100 miles 
beyond its present dimensions, it would require ages of 
unfavourable years, which cannot be adopted without admit- 
ting a permanent change of climate, and of course such a 
permanent change in the earth’s surface as would cause that 
result. 
No doubt it is at first sight startling to suppose that this 
part of Europe stood 3000 feet higher than now. But it 
should be remembered that there is conclusive proof from 
other sources, that Switzerland, even in comparatively recent 
times, underwent several movements both of elevation and 
depression. ‘The period immediately preceding the transpor- 
