28 o 
The Glacial Epoch . 
[May, 
V. THE GLACIAL EPOCH. 
By D. Yewdall Cliff. 
f jjS the Glacial theory as set forth in the “Origin of 
L Species ” generally acceptable ? To me it is not satis- 
fying. The final impression left on the memory is 
this : that Darwin supposed the Earth’s polar axis to have 
always been pretty much at the same inclination to the 
plane of its orbit as it is now, and that during the Glacial 
Epoch the whole Earth was at the same time clothed with 
ice and snow, — that the cold gradually crept down to the 
Equator in a “ circumpolar ” direction. The survival of 
Tropical vegetation, &c., or the crossing the Equator of the 
Temperate forms, is alone a very great obstacle, and his 
explanations are still less assuring. They were before and 
after, which would effectually silence any fancy as to their 
anterior evolution or hereditary revertance ; the fossil record, 
incomplete though it be, tells us plainly to the contrary. 
But there is another supposition, which has doubtless 
often been suggested before, which falls in much more natu- 
rally with Darwin’s theory in general, viz ., that the inclina- 
tion of the polar axis has varied to a far greater degree than 
it does at present ; nay, it may positively have been situate 
in the plane of the Earth’s orbit. Thus there has always been 
a polar region , though probably nothing like as cold as in re- 
cent geological time. I write “ region ” in the singular, 
because, as we can see, if the polar axis ever lay in the 
orbit’s plane radially with the Sun, there would only be one 
climatic pole, and that on the side opposite to the Sun, — as 
the Moon in relation to Earth. This would be the nearest 
approach seemingly to Darwin’s Glacial Epoch, and it the 
severest possible, extending to the present Equator; and the 
South Pole would be the torrid region. A more remote 
contingency would be solar or firmamental disturbances, 
before the present equilibrium was established. 
With a widely, though assuredly slowly, oscillating axis, 
it is easy to see — as its poles travelled all over the world — 
they would carry in a moving patch, as it were, the ArCtic 
flora and fauna, which would still exist where the temper- 
ature allowed, — e.g., mountain-tops; whilst the patch swept 
on, driving the temperate (and the temperate though tro- 
