Preface 



IF asked unexpectedly for an explanation of this 

 volume, I can conceive myself replying that it is 

 " a fortuitous concourse," but on reflexion it appears to 

 have come together through a natural process of evolution. 

 The majority of the articles were originally delivered as 

 lectures or addresses, and some have already been published 

 in scientific journals. On receiving an invitation to 

 render these more generally accessible I very willingly 

 accepted it, and took advantage of the opportunity thus 

 presented for revision and expansion. The introduction 

 of new matter once begun continued till three or four 

 entirely new essays were the result. 



The first article, on the " Age of the Earth," was 

 originally delivered as a Presidential Address to the 

 Geological Section of the British Association at its 

 meeting in Bradford, and the subject-matter is a good 

 deal more extensive than the title indicates ; the next, on 

 the " Figure of the Earth," may be regarded as a con- 

 tinuation of the preceding one, amplifying it in some 

 directions, amending it in others, and at the same time 

 presenting a fresh conception of the form of the earth, 

 which was arrived at independently by two investigators, 

 one following the legitimate but strenuous path of the 

 higher mathematics, and the other snatching at a result 



