Perry.] 70 [December 21, 



found amongst the Alps; he would simply ask whether there were 

 conditions capable of producing the effects in question. 



On the one hand, then, are there any facts indicative of conditions 

 favorable to a sufficient supply of moisture ? In order to the forma- 

 tion of extensive ice-sheets, the water must have come mainly from 

 the ocean. Strange to say, there is the best proof that volcanic 

 agency was very active for some time, about the close of the ter- 

 tiary period. The extensive masses of erupted matter on the Pacific 

 coast and in Central France are, at once, instances and evidence. In 

 connection with these disturbances, submarine volcanoes were no 

 doubt prevalent. These must have heated the waters in the great 

 oceanic basins, and their action being for along time continued, the 

 evaporation would be immense and continuous, furnishing a supply 

 of moisture fully equal to the demand. 



On the other hand, it may be asked whether there be any facts 

 indicative of cold at the period in question. It must be admitted 

 that there is no positive evidence of an elevation of the northern part 

 of North America at that time, and that thus the condition of con- 

 gelation now existing in Switzerland did not probably prevail in this 

 region. But there are cosmical facts suggestive of a degree of cold 

 equal to that required in the production of the effects demanding an 

 explanation. Without dwelling on the supposition that the earth 

 may have been passing through a colder region of space, or on the 

 probability that the sun is a variable body, affording sometimes more 

 and sometimes less heat, he mentioned three points : — 



1 st. Variation in the obliquity of the earth's axis to the plane of 

 the ecliptic. 



2d. Variation caused by the absence of the perihelion in connec- 

 tion with the precession of the equinoxes ; and 



3d. Variation in the eccentricity of the earth's orbit. 



While no one of these variations alone may be sufficient to account 

 for the cold of the ice period, we should remember that they occur in 

 cycles, which maybe represented in round numbers by 10,500, 26,000 

 and 234,000 years each, and that in the course of many revolutions 

 all the tendencies suited to produce cold must have coincided, and 

 that thus, by the combination of intensities, there would result a great 

 winter of the ages. Now let evaporation take place at the same 

 time, and for a long while (and I have evidence bearing on both 

 these points), also let the vapors from the heated basins of the ocean 

 be borne over the cooling regions lying to the north, we have just the 



