86 TRANSACTIONS. 
lasting for thousands of years must have alternated with equally 
prolonged periods of genial conditions, for the latter no less than 
the former are a necessary consequence of extreme ellipticity com- 
bined with the precession of the equinoxes.” 
That the position of the earth in relation to the sun has been 
the great originating cause of the extraordinary climatal conditions 
which prevailed during the glacial epoch is now universally 
admitted, but considerable difference of opinion prevails as to the 
right interpretation of the testimony of the rocks; what the vast 
relics of the “ Ice Age” really tell us as to the physical conditions 
which then prevailed over the surface of our planet. It is 
certainly known that the ice attained to a very great thickness, 
for marks of its presence are to be found on the tops of mountains 
in Canada from 3000 to 5000 feet high. It is certain that our 
own country and part of England was in the same condition as 
Greenland is now, and also that a large part of Northern Europe 
and America, at a comparatively recent period, geologically 
speaking, lay deep buried under a vast sheet of “thick ribbed 
ice,” so thick that only the peaks of the highest mountains stood 
up unburied. It is held by Croll and other eminent geologists and 
physicists that a great ice cap would gather during long thousands 
of years, reaching far down into what is now the temperate zone, 
and that such conditions would prevail for thousands of years 
alternately in northern and southern hemispheres. But there are 
other eminent physicists who maintain that glacial conditions 
during the period of high eccentricity were simultaneous in both 
hemispheres. Able men differ on the matter, and for the present 
we can but regard their various and conflicting opinions as only 
“the guesses of the wise.” While there are differences of opinion 
as to the nature and extent of glacial conditions, there is general 
agreement that the primary cause of such conditions was the posi- 
tion of the earth in relation to the sun. 
Local Notes.—A remarkable example of the work of the great 
ice sheet came under my notice when the railway bridge below 
Dalbeattie was built a few years ago. The foundation for the 
piers of the bridge were laid at a depth of twenty or twenty-five 
feet below the surface, or bed of the stream. The material gone 
through was entirely boulder clay, and at the bottom, strange to 
say, indications of an earlier earth surface and soil were found, 
with fragments of wood and hazel-nuts. 
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