GEOLOGY. 2G9 



pean ocean from the more -westerly portion of that region. Fossil 

 plants also, belonging to a comparatively warm climate, have been 

 found east of the Rocky Mountains, on the coast of the North Sea ; 

 and extensive beds of lignite exist along the eastern flank of those 

 mountains. So far as these phenomena may be of Pleistocene origin, 

 they may be at once accounted for by this theory. 



Before the depression of the North American continent was suffi- 

 cient to admit the gulf stream to flow freely to the Arctic Ocean, the 

 northern part of that continent would be converted into an Arctic sea, 

 and this would correspond to the first part of the glacial drift period 

 in that region. On the gradual elevation of the land after its greatest 

 depression the north-western course of the gulf stream would be again 

 arrested, and the northern portion of the American continent would 

 be again converted into an Arctic sea. The temperature of the region 

 of the eastern portion of North America would probably not be much 

 affected by the alteration in the course of the gulf stream, nor would 

 it probably be very different from that which obtains at present along 

 its eastern coasts. It may also be added, that the continued course of 

 the gulf stream into the Arctic Ocean would very probably generate 

 a cold counter-current from the North Sea across the submerged por- 

 tion of Europe, such as has been above alluded to. The author is 

 anxious to direct the attention of geologists to this view of the subject, 

 in the hope that it may be tested by such further observations as may 

 bear more immediately upon it. It appears to him to satisfy better 

 than any other theory the present known conditions of the great 

 problem which the glacial epoch presents to us. 



DRIFT OF THE NORTHERN AND WESTERN STATES. 



M. DESOR, who has devoted much time to the examination of the 

 drift, or quarternary deposits of the Northern States, recently pre- 

 sented an abstract of his observations to the Geological Society of 

 France. M. Desor classifies the superficial and non-indurated rocks of 

 the waters of the St. Lawrence, and the Upper Mississippi, as follows; 



1st, Alluvium; 2d, marine drift; 3d, fresh- water drift; 4th, drift 

 proper, or diluvium. M. Desor proceeds as follows : 



Alluvium is here, as everywhere, the least developed member ; com- 

 prising the deltas of rivers, sand banks, shallows, and dunes. The 

 marine drift passed at first among the American geologists, under the 

 name of Tertiary, and comprises deposites of clay, sand and gravel, 

 containing marine shells. 



I propose to call them by the name of Laurentian, because these 

 deposites are largely developed in the littoral valleys of the Atlantic ; 

 and principally in the great valley of the River " St. Laurent," (Law- 

 rence,) and its affluents. It is thus I distinguished them from the 

 similar deposites, that contain any fresh water fossils. Along the 

 side of the Laurentian beds, and almost in contact with them, but at 

 a little higher level, is found a series of deposites, externally very 

 much like them, but without marine shells. This formation has no 



