Notices of Memoirs—Dr. M. Manson on Glaciations. 421 
slowly brought into effect from cooling lava and radio-active substances 
by subsequent denudation, would tend to raise the temperature of the 
air, from which it could escape only by slow processes’ under the 
powerful conservative influences of solar radiation. The widespread 
geniality of the succeeding period may be, in part at least, attributed 
to this accession of heat—the geniality compared with that of the 
preceding period, when tropical life flourished at all latitudes. Taking 
the three epochs in succession, Carboniferous, Permian, and Triassic, 
it appears that the Permian was a period of marked temperature 
depression in a series of non-zonal climates.’ 
Pleistocene Glaciation and Conditions.—Pleistocene glaciation followed 
a period during which cold temperate forms of life were for the first 
time distinctly developed over wide ranges of latitude, which, during 
the immediately preceding period, were occupied by temperate forms. 
For the first time also marine life of Arctic habit took possession of 
oceans previously supporting more temperate forms only. The cold 
became so general as to be ‘ worldwide’ in its effects. 
A Review and Comparison of these Glaciations and of Life-—When 
the distribution in latitude of the evidences of early glaciations and of 
life are compared with Pleistocene glaciations and the distributions of 
modern life, it is observed— 
1. That both early and late glaciations and all life prior to the 
modern era were distributed over extreme ranges of latitude and 
apparently without regard to exposure to solar radiation. 
Pleistocene glaciation may have reached its maxima progressively at 
different latitudes, that is, whatever may have been the maximum 
extension of glaciation in the latitude of the tropics, this maximum 
was apparently reached prior to the maximum in, say, latitudes 45 to 
55 degrees; similarly, glacial maxima in these latitudes may have 
preceded maximum glaciations in Polar latitudes. But taken as 
a whole, Pleistocene glaciations were not laid down in accordance with 
present zonally distributed climates. 
2. That early glaciations were preceded, accompanied, and followed 
by a widespread distribution of tropical and temperate forms of life 
and by warm oceans, while Pleistocene glaciation was ‘ phenomenal’, 
was preceded by a period of widespread cold temperate life, and 
accompanied by colder oceans than had previously prevailed. 
3. That the earlier glaciations were followed by periods of wide- 
spread tropical or temperate life, while Pleistocene glaciation was 
followed by a period in which life and temperatures were restricted 
to zones distinctly dependent upon solar radiation for their establish- 
ment and maintenance. 
A deduction which seems fully justified is that up to the culmination 
of Pleistocene glaciation zones of temperature were scarcely perceptible, 
if at all, which deduction is confirmed by both the wide distributions 
of life and the evidences of glacial action in low latitudes in the pre- 
Pleistocene eras. 
The absence of distinct zones of climate is highly significant, and 
' Chamberlin & Salisbury, ii, p. 672. 
2 Neumayr held that there were climatic zones in Jurassic and Cretaceous times ; 
see W. T. Blanford, Address to Geol. Soc., 1890, p. 55.—Ep. Grou. Mac. 
