Trans. N. Y. Ac. Sci. 92 April 14, 
amount of the gas or vapor, a very great number of decrements will 
be needed to produce any sensible effect ; then a less number, and so 
on, until toward the end, when the decrement needed will be small 
and the effect comparatively large. Hence temperature changes 
should have been at first, and for a long time, very slow, and after- 
ward much more rapid. All we know about what did occur is de- 
rived from the study of the plants and animals and noting what 
changes occurred among them ; the results of such study appear to 
be in harmony with what we should expect. The peculiar life of the 
Paleozoic lasted several times as long as that of the Mesozoic, and 
that several times as long as the peculiar life of the Tertiary, and 
in the Tertiary itself the changes were most rapid of all. 
It is also very suggestive that while the changes in the plants and 
animals in the earlier periods were world-wide, the changes in the 
Tertiary were more and more confined to high latitudes, as if the cold 
were settling down from the poles toward the equator. This was to 
have been expected if the early polar warmth was due to that ‘‘ warm 
blanket.” If this was growing thinner, it might be long before any 
sensible effect was produced ; but when*it did appear, it would first 
manifest itself near the poles, where so much depended upon the 
heat’s being retained. 
With this in view, there is no difficulty in seeing why the flora of 
temperate America and of Europe and Asia should have their origin 
in very high latitudes, since, while light and actinic force were always 
fitted for them, it was there a temperature first appeared which was 
adapted to their needs. 
The amount of carbonic acid possible in the atmosphere without 
destroying life is not known, but according to Prof. REMSEN of Johns 
Hopkins University, present animals can breathe an atmosphere 
containing five per cent. of that gas, ‘‘ without experiencing serious or 
even disagreeable effects.” This is one hundred and fifty times, and 
more, the present amount. With animals specially adapted to it, I 
see no reason why the quantity might not in those days have been 
very much greater than five per cent. 
“The Glacial Epoch, and the subsequent Warmth. 
The ‘‘ warm blanket” having been so greatly reduced, the per- 
pendicular axis was permitted to produce its natural effect, and the 
climate ‘‘ became less genial than now.” The cold, moreover, was 
intensified by high latitude uplifts)s We may get some idea of the 
result if we imagine New York State, for example, elevated to a con- 
siderable height, and if the sun never rose any higher than it now 
does on the 21st of March. All present vegetation would die out, and 
