io THE POPULAR SCIENCE MONTHLY. 



ing the interval represented by peat-beds between the first and second 

 bowlder clays, was that of a cool climate, and the interglacial beds 

 have not been traced beyond Scarboro Heights, on Lake Ontario.* 



Facts similar to those from which we have sketched the history of 

 the Ice period in North America, observed in Europe and Asia, afford 

 abundant evidence that the conditions which existed here prevailed 

 over all the northern hemisphere. In South America also similar phe- 

 nomena have been observed and reported by many geologists. Hence, 

 any explanation offered of the records of the glacial period found 

 here must be comprehensive enough to include the whole great field ; 

 and the difficulties which here oppose the acceptance of a theory that 

 is only local in its scope, grow until they become insurmountable. 

 That the conditions which prevailed simultaneously in different parts 

 of the northern hemisphere during the Ice age were synchronous with 

 similar conditions in the southern hemisphere is not proved, nor is it 

 probable that it is susceptible of proof. By many, perhaps most geolo- 

 gists these conditions are supposed to have alternated at the north 

 and south. This much, however, we are justified in asserting, that 

 at an epoch holding the same relative position in geological history 

 north and south of the equator, either simultaneously or alternately, 

 cold climatic conditions prevailed in both hemispheres and left records 

 that are alike in character and import. 



An inquiry into the nature of the cosmical influence which we 

 must credit with the phenomena of the Ice period would lead beyond 

 the scope of this paper, and open questions too broad and suggestive 

 to be settled or even adequately discussed in the space at our com- 

 mand. I shall, however, have accomplished the end I had proposed to 

 myself if I have shown — 1. That the Ice period was a cold period. 2. 

 That the record of the Ice period on our continent is more complete 

 and impressive than it has been represented to be. 3. That it is the 

 product of general and not of local causes. 4. That these causes were 

 not topographical or even telluric, but extraneous and cosmical. 



The question here passes rather into the hands of the astronomer and 

 physicist. The work of the geologist is done when he has shown that 

 the complete solution of the problem does not lie within his domain ; 

 that no telluric agency is adequate to produce the phenomena ; and that 

 some cosmical cause, such as a variation in the heat radiated by the 

 sun, as suggested by Newcomb, changes in the eccentricity of the 

 earth's orbit, as advocated by Croll, or some other general and all-pow- 

 erful influence, must be credited with effects as wide-spread and stu- 

 pendous as those the Ice period has left behind it. 



* .Although this paper is limited in its scope to a consideration of the glacial phenom 

 ena of North America in the Quaternary age, and to certain erroneous notions which 

 are entertained in regard to it, it may not be out of place to say that it is believed by 

 many geologists that there have been several ice periods, and one at least as far back as 

 the Permian epoch. 



