CHAP. X MEASUREMENT OF GEOLOGICAL TIME 237 



the surface of the earth. These studies will, it is believed, 

 place us in a condition to solve most of the problems 

 presented by the distribution of animals and plants, when- 

 ever the necessary facts, both as to their distribution and 

 their affinities, are sufficiently well known ; and we now 

 proceed to apply the principles we have established to the 

 interpretation of the phenomena presented by some of the 

 more important and best known of the islands of our globe, 

 limiting ourselves to these for reasons which have been 

 already sufficiently explained in our preface. 



