422 Notices of Memoirs—Dr. MW. Manson on Gilaciations. 
clearly established the fact that a solar control of climates similar 
to that at present existing did not prevail prior to the modern era,! 
or that some factor was active which did not admit of the zonally 
distributed climates of solar control. 
The distribution of ice and of fossil life during Huronian, Cambrian, 
and Permo-Carboniferous time, and during preceding and succeeding 
eras to the close of Pleistocene time, are so widely at variance with 
a solar-controlled distribution of temperatures like the present that it 
seems impossible to assign these phenomena merely to variations in 
solar radiation. Under solar control, for instance, what would become 
of Polar and mid-latitude life while tropical latitudes were glaciated 
nearly or quite to sea-level ? 
The phenomena of geological and present climates may be interpreted 
under the hypothesis that prior to the Recent or Human Epoch the 
earth was more continuously clouded, and thereby deprived of the 
zonal temperature control of solar radiation.’ 
When these evidences of ice-action and the phenomena of life are 
broadly compared, under this hypothesis, it appears to the writer— 
(1) That accordingly ice-fields were laid down generally without 
regard to latitude, although Pleistocene glaciation reached its maximum 
along the broadest land areas under the north temperate rain-belt, 
and this maximum may have been reached after the inauguration 
of solar control in tropical latitudes. (2) That the earlier glaciations 
were contemporaneous with tropical and temperate land and marine 
forms, and that the greater exposure of the continents to loss of heat, 
and their low specific heat and conductivity, caused them to cool more 
readily, thus frequently forcing land animals to seek warmer conditions 
in the oceans, and from these permanently marine forms of life haye 
descended. (8) That Pleistocene glaciation followed an extremely 
gradual although fluctuating refrigeration of the earth as a whole 
when its crustal condition became more stable than ever before and its 
oceans for the first time fully and completely chilled, and that the 
stress of cold was so general that the oceans did not then offer more 
congenial conditions to even the cold temperate land life of the 
immediately preceding period; that this stress was first relieved in 
regions of least cloudiness by the penetration of solar radiation to the 
surface, and that more moderate conditions spread thence into the 
solar-controlled, zonally distributed temperatures of to-day; that the 
accession of heat through continuous exposure and the trapping of 
solar radiation, converted into long wave-length rays, is a cumulative 
process which has recorded and is yet recording its gradual but 
irregular progressiveness by the removal of Pleistocene glacial 
conditions and the corresponding advance of life. (4) That only 
after the culmination of this marked and phenomenal glaciation did 
temperatures and life pass from a non-zonal to a zonal distribution, 
which manifests itself in zones of life and of climates, and marks 
1 There is an apparently zonal distribution of the very much mixed groups of 
Pliocene life which may have resulted from a similar distribution of temperatures, 
but exceptional conditions warn us against too implicit an acceptance of this conclusion. 
2 See Trans. Tenth Int. Geol. Cong., Mexico, vol. i, pp. 849-405, 1906. 
i. i sl 
