602 SCIENCE PROGRESS 



however, was stated to be negligible. 1 These planets are now 

 introduced in order to confound Drayson. This is not cricket, 

 nor is it mathematics. One cannot dissociate the action of 

 one component of a set of forces from the resultant in this 

 way. Two phrases call for remark — " roughly compounded " 

 and " for a few centuries." Mathematics are an exact science 

 and do not permit of " rough " treatment. Now Drayson's 

 exactness extends demonstrably over several hundred years, 

 and Dr. Hoist's geology unwittingly agrees with Drayson back 

 to 21,000 B.C. 



Are the " few centuries " behind us or still to come ? When 

 will the periodic change again change to make Drayson wrong 

 and the astronomers right ? Are not the planets always with 

 us, exercising their attractions compounded necessarily with 

 that of the sun and moon ? And if Drayson is right in his 

 different axis and different period " for a few centuries," who 

 or what is going to prove him wrong for his longer period ? I 

 regard this criticism as a direct confirmation of Drayson. 



The Position Reviewed 



In tracing the history of this question it will be seen how 

 from an assumption of Newton's, based on insufficient data, 

 and formed before there was any knowledge of geology or of 

 the want of symmetry of the earth, of present gyrodynamics, 

 or of the progressive decrease of the obliquity, astronomers 

 have been enabled by the help of Laplace, now partly dis- 

 credited even by them, to repel and discountenance for a 

 century such attempts as were made by the early geologists 

 to find a cause for a glacial epoch in a change of obliquity ; 

 and great changes of climate depend wholly and solely on the 

 only factor which is able to cause a universal change of climate 

 all over the temperate regions of the globe — namely, a pro- 

 nounced change in the angle between the earth's axis and its 

 orbit. 



The tracing of the circle of the precession movement in 

 accordance with the conclusions of Newton is shown under 



1 On this question Herschel in Outlines of Astronomy, Art. 642, says : "The 

 immense distance of the planets, however, compared with the size of the earth and 

 the smallness of their masses compared with that of the sun, puts their action out 

 of the question in the inquiry of its cause.' 



