326 
Glacial Period in the 
[July, 
we actually have, —nor more than 400,000,000 years ago, or 
we should not have so much as the least observed 
underground increment of temperature. That is to say, I 
conclude that Leibnitz’s epoch of ‘ emergence * of the ‘ com 
sistentur status ’ was probably within these dates* 5 ’* 
III. THE GLACIAL PERIOD IN THE SOUTHERN 
HEMISPHERE. 
By Thomas Belt, F.G.S. 
HE tablets on which the ice of the Glacial period left 
its record in the southern hemisphere are probably 
now mostly covered by the sea, and we cannot trace 
its progress and extent with the same facility and certainty 
as in the northern temperate regions. Yet notwithstanding 
this, and also that the land surfaces of the South that have 
been glaciated have not been studied to anything like the 
same extent as in Europe and North America, points of 
resemblance are apparent, and grounds exist for the belief 
that both hemispheres have passed through a somewhat 
similar glacial experience. 
In our hemisphere, I have sought to show in former 
papers, there were two ways in which the ice spread. One 
was an accumulation on mountain-chains, and a radiation 
from them over the surrounding country. The other, and I 
think by far the most important, was the gradual advance 
of a ridge of ice down the bed of the North Atlantic, and 
probably also of the North Pacific, which blocked up the 
drainage of the continents as far as it extended, and caused 
enormous lakes of fresh or brackish water and immense 
destruction of life amongst the animals that were caught on 
the plains by the rising floods. The marks left by the 
Atlantic ice are seen in Europe, as far as the southern ex- 
tremity of Ireland, and in America, to the south of New 
York, and beyond these points, its further progress can be 
traced by the evidence of the interruption of the drainage 
of the continents as far as the northern slopes of the 
Pyrenees on one side of the Atlantic, and to the coasts of 
* Trans. Roy. Soc. of Edinburgh, vol. xxiii., p. 161. 
