120 The American Geologist. February, i904. 
been, since Permian time, a great change in the borders of the 
Indian ocean, involving the disappearance of the land-formed 
tills. 
5. Total glaciation of the lands and the chilling of the 
oceans to the maximum density of water (32° F.) would cause 
the death of all land life and of nearly all marine life. Where- 
as the life of the present is paleontologically known to be a 
lineal descendant from pre-glacial ancestors. It may be urged, 
however, by Mr. Mason, that his presentation of his theory 
allows not only for non-glaciated regions where life may have 
been perpetuated, but that his plate (opposite page 68 j and 
statements on pages 74 and 85,* show that the zonal climates 
which were dependent on the full ingress of the sun's rays be- 
low the cloudy canopy, may have begun their action in early 
Quaternary time, and that the existence of solar warmth be- 
gan in the latitude of the tropics and progressed poleward 
through Tertiary and Pleistocene time. 
6. It has been assumed that exogenous trees, growing by 
annual rings added to the outside, prove the action of alternat- 
ing summer and winter and hence solar climates. Exogens are 
sparsely found in the rocks as early as Devonian time, and Dr. 
Sardesonf has called attention to a twisted form of stem ex- 
hibited by certain shallow-water monticuliporoids of the Lower 
Silurian, which he interprets as possibly due to heliotropism, 
and hence an indication of direct sunlight. If these indications 
of early solar climate can be explained conformably with Mr. 
Manson's theory, or a modification of it, certainly a most seri- 
ous obstacle will be overcome. 
Whatever may have been the condition of the immediate 
surface of the earth, if it was for ages covered by a cloudy 
canopy, the sun's light and warmth must have been exterior to 
the canopy and must have acted on the mists of that canopy in 
a manner similar to the sun's action on modern mists and 
clouds. Indeed, it may be assumed, reasonably, that the exter- 
ior of the canopy was subject to solar control, and probably 
passed annually through a succession of changes comparable to 
the solar climatic changes which now annually encompass the 
earth. The only effect of these climates in the clouds, which 
• See also under 2, p. 52, "Elevated continental areas," etc., and (d) pages 
67 and 68. 
t Ambrican Geologist, vol. xxvii, p. 388, "Meteorology of the Ordoviiian." 
