PERMO-CARBONIFEROUS CLIMATIC CHANGES 631 
through about 35° of longitude. In South Africa glacial material 
has been found from 25° to 33°S. and through 11° east and west, 
while in South America it appears to occur as far north as 30°S. In 
_ Australia there is proof of a recurrence of glaciation with a thin 
interglacial series (Greta), 230 feet in thickness including coals, 
between the bowlder beds. 
Exaggerated temperature effects oj elevation—The occurrence of 
glacial phenomena within the tropics was presumably due in part to 
an extension of the southern cold with the favoring assistance of 
ocean currents and perpetual atmospheric ‘‘lows,’’ resulting in part 
from continental relations and topography. The writer is strongly 
disposed further to attribute a very important part in the refrigera- 
tion, and more particularly the singular localization of the latter, to 
the height of the land on which the glaciers developed. Mention has 
already been made of the fact that the great coal measures series of 
the Gondwanas, of South Africa, and of South America are vast 
fluviatile or lacustrine deposits many thousands of feet in thickness, 
resting unconformably on old erosion basin floors. The enormous 
accumulations of coarse conglomeratic material in the eastern regions 
testify to the steep gradient of the drainage systems. ‘The presence 
in nearly all regions of the great unconformity is itself evidence of the 
vigor of the post-Carboniferous uplift in the GANGAMOPTERIS prov- 
ince. In Africa and South America, at least, large portions of the 
land masses probably stood at a considerable elevation during glaci- 
ation. It is not clear that in Australia or India the source of the ice 
was near sea level, though on both the latter there is abundant evi- 
dence of the deposition of bowlders dropped from floating ice. Cur- 
rents of cold water sweeping along the Antarctic continent may well 
have carried icebergs for long distances to the north in the Australian 
region. 
A relatively high altitude for the areas of ice accumulation would 
not only enormously assist in explaining the peculiar geographical 
distribution of the ice phenomena, but it would seem to offer a satis- 
factory accounting for the differences in climate, as indicated by the 
floras, between the Northern and Southern regions. It has been urged 
by Chamberlin‘ that a diminution of the CO, of the atmosphere, with 
t Journal oj Geology, Vol. VII, 1899, pp. 545, 667, 751. 
