274 SCIENCE PROGRESS 



The main facts are : 



1. The continuous decrease of the obliquity of the ecliptic during the 

 last 3,000 years. 



2. The steady reduction of the O.E. by half a degree during that period, 

 and the increasing rate of secular change as we go back in time. 



3. The past and present retreat of the polar ice-caps accompanying the 

 diminishing obliquity. 



The diverse statements made regarding the O.E. from time to time by 

 astronomers are : — 



(a) The O.E. is constant at 23° 28', though it varies some 48" per century 

 (Herschel's Outlines of A stronomy) . 



(6) That only a change of O.E. to the extent of 1° 41' on either side of the 

 " invariable plane " is possible (Laplace). 



(c) Some years after Laplace's researches, Leverrier found that the 

 possible change on either side of the " invariable plane " must be increased 

 to 4° 52' (Leverrier). 



(d) It has since been found that Laplace and Leverrier are both wrong, 

 and that there are no limits to changes in the obliquity (Encyclopedia Brit- 

 annica, igo6). 



(e) But the above authority says that to bring about a change of two or 

 three degrees would take a million years of our epoch. (See fact (2) above.) 



(/) That to accept Drayson, i.e . not to accept the pole of the ecliptic as the 

 centre of the polar movement, was equivalent to throwing overboard the 

 laws of gravity (Astronomer Royal and others). 



(g) But in order to explain why there is a decrease in O.E. which, if the 

 text-books are right, should not occur, astronomers have to admit, in spite 

 of gravity laws, that " for a few centuries " the ecliptic pole is not the centre 

 of the circle made by the pole of the heavens. Now to make all these state- 

 ments appear to agree, we want primarily an explanation, not of the " few 

 centuries," but of the at least thirty centuries during which the O.E. is 

 known by the records to have been decreasing. (See fact (i) above.) 



The geological deduction to be drawn from all that I have written is as 

 sound as any other geological fact which has been accepted as conclusive 

 in geology, and it is my hope that geologists will see the force of all the evidence 

 in favour of a recent glaciation and will accept the deduction as a working 

 theory without waiting for a mandate from astronomers, who, as is made 

 very evident by the above tabulated statements, are groping amongst diffi- 

 culties, which have only been created by their own adhesion to paradox, 

 difficulties which will entirely disappear when the question is openly handled 

 on Drayson's lines. 



That astronomers are unconsciously drifting into the Drayson position 

 is apparent from the quotation referred to under {g) from Sir Oliver Lodge's 

 Pioneers of Science, in which he says that the path of the pole " for a few 

 centuries may without error be regarded as a conical revolution about a 

 different axis with a different period," and adds that " Lieut .-Col. Drayson 

 writes books emphasising this simple fact under the impression that it is a 

 discovery" ! 



The dilemma of orthodoxy is sufficiently obvious. 



In this letter I have endeavoured to keep the geological evidences apart 

 from the more technical astronomical data as far as possible. I maintain 

 that the former establish a reasoned and reasonable conviction quite as 

 worthy of forming part of the geological structure as the assumption of the 

 gradual evolution of organic existence in the fossils of the rocks ; while the 

 latter invite attack by the paradox involved by a changing length of radius, 

 during a long period, to a movement which is regarded by astronomers as 

 describing a circle. 



Convinced that in the material universe paradox should have no place. 



