Schaw. — On the Last Glacial Epoch. 523 



at any date ; it fixes the apparent motion of the north pole of 

 the axis of daily rotation with accuracy, and also the corre- 

 sponding motion of the south pole ; it explains and enables us 

 to calculate easily and certainly the true apparent position of 

 every star hundreds of years ago and hundreds of years hence ; 

 and it shows us that, under the present conditions of the globe, 

 the period required for a complete second rotation is 31,686 

 years (Plate XLV., fig. 4), and that during this period the 

 obliquity of the axis of daily rotation to the axis of the plane 

 of the ecliptic would have attained a maximum of 35° 25' 47" 

 in the year 13,544 B.C. The obliquity would have been about 

 30° in the year 21,460 B.C., and would have returned to 30° 

 again in 5,624 B.C. Between those dates — that is, for 15,866 

 years — glacial conditions, more or less accentuated, would 

 have prevailed in both hemispheres : that is, the arctic and 

 antarctic circles would have been brought from 12° to 6° nearer 

 to the equator than at present, the tropical zone having been 

 also proportionately widened, and thus much greater extremes 

 of temperature would have been experienced, especially in 

 what are now temperate zones. What the precise results of 

 this great increase in the obliquity of the ecliptic would be 

 no one probably would have been able to predict ; but that 

 such a great change in that element of the earth's position, 

 with reference to its orbit round the sun, on which our 

 climatic conditions mainly depend, would accomplish immense 

 alterations in existing conditions no one can doubt. An in- 

 cident recounted in General Drayson's book is so suggestive 

 that it is worth reproducing here. He says, " Some years 

 ago, when standing on the banks of a lake in Nova Scotia (a 

 locality well suited to the study of the evidence of the Glacial 

 period), I observed that the hard rocky shore was cut and 

 marked by the glaciers and icebergs of the boulder period. In 

 various inland localities were enormous boulders, which had 

 been carried many miles from the parent rocks, and deposited 

 in what was now a vast forest. My only companion was Paul, a 

 Micmac Indian. Pointing to the boulders and the marks on the 

 rocks I said, 'Paul, how do you account for all this?' Paul, 

 without any hesitation, replied, 'Longtime ago more winter 

 in winter, more summer in summer. More winter make more 

 snow, more icebergs ; more summer melt snow quicker, float 

 icebergs more than now. That what I think." I have no doubt 

 that the Indian, a careful observer of the natural effects and 

 their causes in the climatic conditions in which he lived, was 

 right in his conclusion. There was more winter, but there was 

 also more summer, and, as Professor Tyndall states, heat is as 

 necessary as cold to produce glaciers and to develope their full 

 effects. Sir Eobert Ball has calculated that, with the present 

 obliquity of the ecliptic, each hemisphere of our globe receives 



