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POPULAR SCIENCE REVIEW. 
tendency to vary from their types both in Europe and in Arabia, while the 
rest remained persistent in form. 
The Glacial Period in America. — Mr. Thomas Belt has sent us a reprint 
of a memoir published in the Transactions of the Nova Scotian Institute of 
N'atural Sciences [Vol. I. Part 4]. It is upon the above subject, and ex- 
presses the views of the author, who is evidently well acquainted with the 
.glacial geology of North America. The following are the principal conclu- 
sions which Mr. Belt has drawn : — 1. The arrangement of the heaps of granite 
in the flanks of hills, and the distribution in them of grain gold in Nova 
Scotia, are opposed to the theory of the submergence of the country, either 
during or since the Glacial period. 2. The submergence of part of eastern 
North America, during which the marine beds of the Champlain period 
were formed, was not participated in by the southern coast of Nova Scotia. 
3. To explain the movement of land ice from the Arctic regions southwards, 
it is not necessary to suppose that the continent to the north must have 
been greatly elevated, nor do the facts connected with the distribution of 
the drift agree with such a supposition. 4. That there was some elevation 
of northern lands during the Glacial period is, however, probable : — Firstly , 
because all the oscillations of level of the lands in the Northern Hemisphere 
since the Glacial period, with which we are acquainted, have been greatest 
towards the pole ; and secondly , because a rise of land sufficient to prevent 
the entrance of heated currents to the polar basin, would occasion a great 
accumulation of ice in the circumpolar regions, by the heat of the tropical 
and sub-tropical waters being spent in evaporation instead of, as at present, 
in melting the ice within the Arctic circle. 5. The drift-beds were formed 
during the retreat of the ice, and not during its greatest development. 6. 
Terraces and stratified beds in lateral valleys, were formed when these were 
filled with water, dammed back by the glaciers that still flowed down the 
main valleys. 
The Glacial period , in its relation to the eccentricity of the" earth’s orbit, 
is the subject of a highly philosophical essay, which appeared in the Philo- 
sophical Magazine for February. The paper should be carefully studied by 
those of our readers who are interested in the point it deals with. The fol- 
lowing paragraph will give an idea of the author’s views. u When the ex- 
-centricity reaches a high value and one of the solstice points is in podhelion, 
the difference between the temperatures of the two hemispheres must be 
very great. The hemisphere which has its winter in aphelion , and mider a 
condition of glaciation, is much colder than the opposite hemisphere, which 
has its winter in perihelion and enjoying an equable climate ; and the con- 
sequence is, the aerial currents from the pole to the equator must be much 
stronger on the colder hemisphere than on the warmer, because the dif- 
ference between the temperature of the pole and the equator is greater on 
the former hemisphere than on the latter. When the northern hemisphere, 
for example, is under glaciation, the north-east trade-winds will be much 
stronger than the south-east. The medial line between the trades will con- 
sequently lie a considerable distance to the south of the equator. The effect 
of the northern trades blowing across the equator to a great distance will be 
to impel the warm water of the tropics over into the Southern Ocean. And 
this, to an enormous extent, will tend to exaggerate the difference between 
