114 ^^^^^ America?i Geologist. August, i899 
of waves is accredited with triturating and depositing these 
materials on hills and valleys, and strewing them down the 
sides of hills, and in some unexplained way, these cobbles, 
gravels, and sands get mingled in bogs with the remains of 
extinct gigantic mammals. 
Had Prof. Branner been trying to prove the glaciation of 
the areas described, he could hardly have made the case strong- 
er than he has. It could only be made clearer by tracing the 
varieties of stone back to their sources; by showing that the 
deposits were thinner and more modified than similar deposits 
further'from equatorial regions by reason of the shorter dura- 
tion of glacial conditions, and the greater time and exposure to 
modifying agencies; by giving the species, food, and habits of 
the extinct mammals, comparing them with the corresponding 
animals elsewhere abundant during the cold temperate periods 
preceding the Ice age, and by showing that their extinction 
was caused at the same time and by the same agencies which 
are known to have rendered cotemporaneous life extinct else- 
where. 
But suppose we accept Prof. Branner's interpretations of 
the origin of Brazilian drift as correct, we are nevertheless 
confronted with glacial phenomena in other tropical countries 
which do not yield to a like line of argument, to say nothing 
of the enormous glacial action in the temperate zones, the ac- 
counting for which is only different in degree, and to account 
for which many able geologists reverse the order of upheaval? 
and depressions suggested by Prof. Branner.* 
The same laws and conditions which would arrest solar 
energy and permit the gradual chilling of our globe from ultra 
torrid temperatures at all latitudes, down successive gradations 
until the temperate and polar regions were gripped in ice 
thousands of feet thick, and until the oceans at all latitudes 
were intensely cold, would not except even tropical land areas. 
to have taken place elsewhere, and appealed to by many geolog-ists 
as the cause of a similar deposition of drift in temperate latitudes; 
it will be seen by examining any standard physical atlas that the 
coast of Brazil adjacent to the mouth of the Amazon is generally 
conceded to be gradually sinking. 
*When so close an observer as Dr. Branner has to resort to a 
reversion of the order of upheavals and depressions in Brazil to 
account for phenomena and facts corresponding to those found in an 
admittedly glaciated region in North America the homely Scotch 
verdict of "not proven" must be recorded against his conclusions. 
