ARTICLES 599 



vinced on astronomical grounds that this must have been the 

 actual state of things." 



Now nothing is more certain than that the glaciation was 

 simultaneous at both poles, and not alternate, as established 

 by researches in America previous to the South Polar Expe- 

 dition. The discovery made subsequently in the Antarctic of 

 the retreat of the ice there — and we know it is retreating at 

 the North Pole — settles the matter once and for all, that 

 glaciation and its converse in the two hemispheres proceeded 

 simultaneously, so that the foregoing astronomical theory there- 

 fore must perforce be abandoned. 



How far these failures have influenced astronomers in 

 general to take stock of the position can only be surmised, 

 though it is evident that their attention has been turned to 

 the question of the invariable plane, because in the Ency. Brit. 

 of 1906 we have the following : 



" Attempts have been made by Laplace and his successors 

 to fix certain limits within which the obliquity of the ecliptic 

 shall always be confined. The results thus derived are, how- 

 ever, based on imperfect formulae. When the problem is con- 

 sidered in a more rigorous form, it is found that no absolute 

 limits can be set. It can, however, be shown that the obliquity 

 cannot vary more than two or three degrees within a million 

 years of our epoch." 



As no cycle of precession under the circumstances could 

 be more than tens of thousands of years, it will be seen that 

 this last statement regarding a million years being required 

 is not founded on any known fact, and may be regarded as 

 merely a step in the process of climbing down from an insecure 

 position, and as a concession to pious belief. 



Thus one of the main supports for the fiction of a prac- 

 tically fixed obliquity, which barred the way to geologists, 

 is now removed, and the next investigation in a more " rigor- 

 ous " form will cause the collapse of the whole structure. 



In the efforts of astronomers working with a wrong centre 

 to meet the difficulties arising therefrom, and to standardise 

 them, so to speak, they have unconsciously produced a most 

 significant corroboration of Drayson's discovery. 



An empirical formula for finding the obliquity of the Ecliptic 



