254 W. Hopkins on Changes of Climate. 
The present mean annual temperature of Snowdon is about 
49°'5 F., or 17°95 above the freezing temperature. Assuming 
the general elevation of western Europe, Snowdon would stand 
on a wide elevated table-land, and we may take the decrease of 
temperature at 1° F. for about 450 feet.* This would give the 
height of the line of 32° equal to rather more than 7800 feet, 
and, supposing the snow-line 2200 feet higher, we have 10,000 
feet for the height of this latter line. Now to produce glaciers 
of considerable magnitude on Snowdon, its summit must proba- 
bly rise some 1000 feet above the snow-line, or to the height of 
11,000 feet. Hence the whole region must be elevated between 
In higher latitudes the required elevation would be smaller; but 
speaking generally, in order that glaciers should exist on our pres 
ent mountains of sufficient magnitude to descend down to thet 
present bases, in consequence of a general elevation of western 
Europe, it would be necessary that that region should © raised 
into an elevated range from the polar circle to the south of the 
ture from January to July, would be 619 F. instead of wir 
present, and the quantity of snow falling during the year in 
doubtless be much diminished by the entire absence of seal 
the surrounding region. It would seem probable that the pos 
tion of the snow-line would be as much raised by these causes, 
as it would be lowered by the diminution of temperature. “a 
over, it is probable, that the glaciers would not descend so far 
low the snow-line as at present, on account of the diminution I 
ir mass, arising from the diminished quantity of a 
conceive it probable, therefore, that the Alpine glaciers wou rer 
end, in the case now contemplated, to points less ¢© 
* I take this num e the elevati 9 of the oy 
rounding region sem og swing oma Sg fabloland than that eae hs 
around the Alps. 
