596 SCIENCE PROGRESS 



reviews. In reality he was merely engaged in helping astrono- 

 mers to define the true circle and period of precession by 

 supplying information which they evidently lacked. In doing 

 so he removes a paradox, and his views, instead of being re- 

 garded with disfavour, should, be welcomed as a revelation. 

 It must be remembered that Drayson had no primary interest 

 in geology to make it his aim to prove great changes in obliquity 

 to produce an Ice Age, but he was an astronomer to whom 

 this aspect of the question came as an after-thought, and was 

 considered by him as a side issue. 



The opinion of European astronomers has not been unani- 

 mous on this subject. The late Astronomer Royal of Sweden, 

 for instance, held the opinion that there were no limits to 

 possible changes of obliquity ; and since Drayson first an- 

 nounced his discovery, a significant change of attitude towards 

 this question of obliquity is observable, though astronomers 

 may not be conscious of its consequences. In fact they have 

 drifted into a position which scarcely leaves any course open 

 to them other than to accept Drayson. 



It is instructive to trace the development of the dogma for 

 which Newton is chiefly responsible, and thus to grasp the 

 inherent weakness of the astronomical position. Newton, after 

 discovering the Laws of Motion, found himself called upon to 

 explain the Precession of the Equinoxes, which Copernicus was 

 the first to state to be a motion centred on the pole of the 

 ecliptic. This Newton attributed to the gravitation pull of 

 the moon, sun, and planets on the belt of protuberant matter 

 round the earth's equator. Knowing no other play of forces 

 such as modern gyrodynamics have disclosed, and judging the 

 earth to be symmetrical in shape, this was the best solution 

 he could give, though it was scarcely in accord with one of 

 the corollaries of his Laws of Motion, which demonstrates that 

 one body may be considered to act on another body at its 

 centre of gravity, irrespective of figure. Newton in his Prin- 

 cipia states regarding the above corollary that with an oblate 

 spheroid this is not " exactly true." Why exactly, one may 

 ask? I only wish, however, to emphasise the fact that Newton 

 was wrong in his assumed centre for the reason given below. 

 From gyrodynamics we know that a similar precession movement 

 can be induced by the friction of the tides on a rotating earth 

 or by a slight alteration in the centre of gravity of a revolving 



