Schaw. —0/i the Last Glacial Epoch. 531 



well adopt the expression as regards the second rotation of the 

 earth. 



To sum up. It has been established by unassailable 

 evidence that the slow movement of the prolongation of the 

 earth's axis of daily rotation in the northern heavens, which 

 has long been known, is the result of a slow second rotation 

 of the earth on an axis the poles of which are 6° distant 

 from the poles of the ecliptic, and having a right ascension 

 of 18 hours ; that this slow second rotation is the cause also 

 of the precession of the equinoxes and the varying obliquity 

 of the ecliptic ; that this obliquity would have attained 

 gradually to its maximum of 35° 25' 47" about 15,448 years 

 ago, and then gradually declined again until the present time. 

 About 7,524 years ago, or 5626 B.C., the period of extreme 

 obliquity would have expired, after having endured for about 

 16,000 years. During that period the arctic and antarctic 

 circles would have approached the equator from 12° to 6° 

 nearer than at present, and consequently climatic condi- 

 tions would have been greatly changed, especially in the 

 zones south and north of the present arctic and antarctic 

 circles. The tropical regions would also have been similarly 

 extended. All this follows if we admit that the earth has 

 been rotating on its second axis during this period of the past 

 as it is now. The geological records of the Northern Hemi- 

 sphere show that during this period there was an ice age in the 

 above-mentioned zone extending farther south and being 

 more intense in its action in some places than in others, for 

 reasons which we can in a great measure discern. This ice 

 age, then, we must infer was the result of the increased obli- 

 quity mainly. 



In the Southern Hemisphere there are similar records of 

 an ice age, modified by local circumstances as in the Northern 

 Hemisphere. This ice age is also comparatively recent, and 

 its limits correspond with those in the Northern Hemisphere. 

 We are naturally led to suppose that its cause was the same 

 as that in the Northern Hemisphere, and that it occurred at 

 the same time. It remains for geologists to say, after full in- 

 vestigation and consideration, whether there are any reasons 

 which are insuperable, and which oblige us to disbelieve that 

 the great increase in the obliquity of the earth's axis which 

 occurred in both hemispheres at this time produced the effects 

 here which are comparable with those in the Northern 

 Hemisphere. 



Appendix A. 



In consequence of what was said in the short discussion 

 which I invited at the close of my address, I would add that, 

 although the astronomical facts which follow from the dis- 



