328 J.D. Dana on American Geological History. 
have been produced over Europe, partly at least, by a diversion 
of the Gulf Stream from its present position. He seems in his 
paper to attribute too much effect to the Gulf Stream, and too 
little to the prevailing currents of the atmosphere. But, setting 
this aside, it is unfortunate for the hypothesis, that there is no 
reason to suppose that America was not then as much in the wa 
of such a diversion as now. ‘The small changes of level whic 
the Tertiary and Post-tertiary beds of the Gulf have undergone, 
prove that the gate of Darien was early closed, and has since 
continued closed. America, as facts show, has not been sub- 
merged since the Tertiary to receive the stream over its surface. 
If it had been, it would have given other limits to her own drift 
phenomena; for it is an important fact that these limits in 
i urope show the very same difference in the eli- 
: : aa 
On the question of the drift, we therefore seem to be forced 
to conclude, whatever the difficulties we may encounter from the 
conclusion, that the continent was not submerged, and therefore 
that icebergs could not have been the main drift agents: that 
riod was a cold or glacial epoch, and the increase of cold was 
probably produced: by an increase in the extent and elevation of 
northern lands. Further than this, in the explanation of the 
drift, known facts hardly warrant our going. oh 
_ Tf, then, the Drift epoch was a period of elevation, it must 
have been followed by a deep submergence to bring about the 
depression of the continent already alluded to, when the ocean 
stood four hundred feet deep in Lake Champlain, and a whale— 
for his bones have been found by the Rev. Z. Thompson of Bur- 
lington—was actually stranded on its shores; and when the u 
terrace of the rivers was the lower river flat of the valleys. ‘Thi 
submergence, judging from the elevated sea-beaches and terraces, 
the great alluvial plain constituting the upper terrace, 80 1- 
mensely beyond the rE saad of the present streams? Perhaps, 
as has been suggested for the other continent, and by Agassiz 
* Moreover, the Gulf Stream i known to deep as to be 
turned around to the northward * the isduinrin! doves ct tin oom ne 
: t the age 
given the stream a chance over the land: and even then, if the West Indian Islands 
“a not also deeply sunk in the ocean, a large part of the current would still have 
