158 
PHYSICAL HISTORY OF THE 
are unquestionably drift phenomena, they pre¬ 
sent in their wider extension, and especially 
in the northern part of Brazil, as will hereafter 
be seen, some phases of glacial action hitherto 
unobserved. Just as the investigation of the 
ice-period in the United States has shown us 
that ice-fields may move over open level plains, 
as well as along the slopes of mountain valleys, 
so does a study of the same class of facts in 
South America reveal new and unlooked-for 
features in the history of the ice-period. Some 
will say, that the fact of the advance of ice¬ 
fields over an open country is by no means es¬ 
tablished, inasmuch as many geologists believe 
all the so-called glacial traces, namely, strias, 
furrows, polish, etc., found in the United States, 
to have been made by floating icebergs at a 
time when the continent was submerged. To 
this I can only answer, that in the State of 
Maine I have followed, compass in hand, the 
same set of furrows, running from north to 
south in one unvarying line, over a surface of 
one hundred and thirty miles from the Katali- 
din Iron Range to the sea-shore. These fur¬ 
rows follow all the inequalities of the country, 
ascending ranges of hills varying from twelve 
