DEEP-SEA DREDGINGS. 5 
has been considered by geologists as a fixed fact, whatever may 
have been the discrepancies among them as to the extent of these 
continental masses of ice, their origin, and their mode of action. 
There is, however, one kind of evidence wanting to remove 
every possible doubt that the greatest extension of glaciers in for- 
mer ages was connected with cosmic changes in the physical con- 
dition of our globe. All the phenomena related to the glacial 
period must be found in the southern hemisphere with the same 
characteristic features as in the north, with this essential differ- 
ence, that everything must be reversed ; that is, the trend of the 
glacial abrasion must be from the south northward ; the lee side 
of abraded rocks must be on the north side of hills and mountain 
ranges, and the boulders must have been derived from rocky ex- 
posures lying to the south of their present position. Whether 
this is so or not, has not yet been ascertained by direct observa- 
tion. I expect to find it so throughout the temperate and cold 
zones of the southern hemisphere, with the sole exception of the 
present glaciers of Terra del Fuego and Patagonia, which may 
have transported boulders in every direction. Even in Europe, 
geologists have not yet sufficiently discriminated between local 
glaciers and the phenomena connected with their different degrees 
of successive retreat on one hand, and the facts indicating the ac- 
tion of an expansive and continuous sheet of ice moving over the 
whole continent from north to south. Unquestionably, the abra- 
sion of the summits of the mountains of Great Britain, espe- 
cially noticeable upon Schiehallion, is owing to the action of the 
great European ice-sheet during the maximum extension of the 
; glacial phenomena in Europe, and has nothing to do with the lo- 
cal glaciers of the British Isles. 
Among the'facts already known from the southern hemisphere 
are the so-called rivers of stone of the Falkland Islands, which 
attracted the attention of Darwin during his cruise with Captain 
Fitzroy, and which have remained an enigma to this day. I be- 
lieve it will not be difficult to explain their origin in the light of 
the glacial theory, and I fancy now they may turn out to be noth- 
ing but ground moraines, similar to the * Horsebacks” of 
You may ask what the question of drift has to do with paa 
sea dredging? The connection is closer than may at first appear. 
If drift is not of glacial origin, but tħe product of marine cur- 
rents, its formation at once becomes a matter for the Coast Survey 
