W. Hopkins on Changes of Climate. 257 
line with the level to which the glaciers descend. . All we seem 
to know is, that glaciers descend to the margin of the sea; but 
before we can reason conclusively on this, as a case analogous to 
that of Snowdon or of other mountains in our own islands, it. is 
hecessary to know more than I have at present been able to as- 
certain, respecting the height and configuration of the mountains 
from which the glaciers descend. Mr. Darwin in his. Journal 
quotes Cook’s description of the island, but it contains no accu- 
rate information on the points in question, although it would lead 
tothe inference that the snow-line must be considerably below 
the line of 32° F, 
‘ It would seem very possible then, that the snow-line on Snow- 
don in the present hypothetical case might not be higher than 
the line of 32° F., the height of which is above estimated at 
00 feet. Glaciers might thus descend from a snow-line little 
More than 2000 feet high to the level of the sea. 
_27. If, in addition to the hypothesis of the absence of the 
Gulf. ream, we adopt that of a cold current from the north, 
‘Weeping over the submerged portions of northern and western 
Europe, we shall have an additional cause which might probably 
"lower the mean annual temperature of Snowdon and the neigh- 
§ Tegion by 3° or 4° below that above assumed. Such a 
current would also tend to equalize the summer and winter tem- 
Peratures, since its effect would there be principally or entirely 
ced on the summer temperature, which might possibly be 
ered 6° or 8°. The snow-line would thus be brought at 
least 1000 or 1200 feet lower than above supposed. This would 
be sufficient to account for glaciers descending to the sea, not 
ouly on Snowdon, but also on the lower mountains of the west 
of Treland / 
28, Conclusions, but somewhat vague, have been drawn re- 
SPecting the former possible existence of glaciers in western Eu- 
the two regions has been frequently, I think, overlooked. In the 
“ase we have been discussing, the mean annual temperatures in 
~~ sponding latitudes in the two hemispheres would be almost 
®xactly the same, and probably the quantity of moisture in the 
peuosPhere and the quantity of snow in similar positions might 
+ lng the same; but the greater extent of land which must 
© €Xisted in the northern hemisphere, as compared with the 
Southern, in the more recent geological periods, must have ren- 
But in this comparison the relative heights of the mountains in 
