An 
‘ 
Bs 
- hemisphere and to warm the other, toaccumu 
bring about any important alteration—-the geo- 
graphical causes of glaciation remaining unchanged?” If the 
question is put thus, and it is the only form in which it can be 
pat to be consistent with the theory which Mr. Wallace him- 
self advocates, then my reply is, that the change from the 
distant sun in winter and near sun in summer to the near sun 
in winter and distant sun in summer, aided by the change in 
the physical causes which this would necessarily bring about, 
would certainly be sufficient to cause the snow and ice to dis- 
appear without any change in the geographical condition of 
things. The combined influence of the astronomical and phys- 
ical causes, when the winter solsticé is in perihelion, is perfectly 
sufficient to undo all that they had previously done when the 
solstice was in aphelion. When the action of the causes is 
simply due to an elevation of the land, as some have argued, 
sai it would not likely have disappeared till the land became 
Owered. But it was the result of no such cause. It was due, 
hot to an elevation of the land, but to a number of physical 
sauses, brought into operation by a-high state of eccentricity. 
This Mr. Wallace fully admits and maintains. A certain geo- 
and this was really all that geographical conditions had to doin. 
the matter, Let this be observed, however, that the same geo- 
of the cooling of the other. It is the transference of heat by 
ion to the one in 
€ latter warm. Hence a change in geographical conditions is” 
‘Northern or the southern. 
€ tendency of the combined influence of all the causes— 
astronomical, physical, and geographical—is to cool the one 
el 
late the ice on the 
