THE DRIFT-DEPOSITS OF THE NORTHWEST. 289 



This theory, so novel, so startling, met with various acceptance. 

 By some it was loudly scouted as the product of the imagination solely ; 

 and was classed by Prof. B. Studer, a savant of the Continent of Eu- 

 rope, with the poetical Indian legends, wherein the periods of heat and 

 life are made to alternate with periods of freezing and death. But its 

 force lay in the inherent evidence of candor, and honesty in the state- 

 ment of facts about which there could be no dispute. By the most 

 enlightened geologists, both of the Old World and the New, it was re- 

 ceived as a flood of light cast on what had befox - e been dark and un- 

 explained ; and it was accepted with some caution and exceptions by 

 such men as Prof. Buckland, Sir Charles Lyell, and Prof. Edward 

 Hitchcock. At the present day but few geologists can be found in 

 this country who do not admit the reality of the glacial epoch. 



But, while it is true that but few geologists can be found in this 

 country who do not admit the truth of the glacier theory of Prof. 

 Agassiz, it is also true that a great many, perhaps the majority, also 

 adhere to the iceberg theory of Peter Dobson. The two theories at 

 first came in violent conflict. They diverged at the outset. One re- 

 quired the continent below the ocean, and the transportation of bowl- 

 ders and other drift by floating ice ; the other required it elevated 

 high above the ocean, and the transportation of the drift by ice in the 

 form of continental glaciers. How, then, can the same person hold to 

 both theories ? 



Soon after the promulgation of the glacier theory by Prof. Louis 

 Agassiz, Mr. Charles McLaren attempted to make it harmonize with 

 the iceberg theory. He was seconded in the effort by Prof. Edward 

 Hitchcock, who invented the term aqueo-glacial, to express the force, 

 or forces, that operated to disperse the materials of the drift. In ex- 

 plaining the meaning of that term, he says, however, he cannot admit 

 the glacier theory of Prof. Agassiz, and apply it unqualifiedly to this 

 country ; but, while acknowledging himself greatly indebted to Agas- 

 siz, he thinks that icebergs were the principal agents in transporting 

 the drift. In the years 1841 and 1842 Sir Charles Lyell visited this 

 country. His observations on the drift, published in various scientific 

 journals, and repeated in his book of " Travels in North America," in 

 1845, furnish the basis for the most plausible union of these two 

 theories. He divides the drift epoch into four parts : 



1. The period of emergence of the land, during which some of the 

 bold, rocky escarpments of the continent were formed. 



2. A gradual subsidence and moderate submergence of the interior 

 portions of the continent, during which icebergs floated over the sur- 

 face of the ocean, grinding and marking the rocks. 



3. The deposition of the clay, gravel, and sand, of the drift, with 

 occasional fragments of rock, the last through floating ice. 



4. Period of reelevation and formation of lake-terraces. 

 Although not professedly aiming to reconcile the iceberg theory 



VOL. III. 19 



