viii PREFACE. 



that the deficiency occurring in one, is supplied in 

 some other island of analogous structure ; and it has 

 every where been attempted, so to refer and arrange 

 the several facts, as to enable the reader to supply 

 for himself whatever may be wanting towards a 

 minute account of each ; as far at least as they are 

 known to myself. 



In thus approximating the islands of analogous 

 structure, for the purpose of rescinding repetitions 

 or superfluities, an attempt has also been made to 

 unite them, as far as possible, into groups regulated 

 by their natural affinities. Thus they mutually assist 

 in explaining the structure of each other ; that which 

 is obscure in one, being elucidated by some other of 

 the group ; while the interest of the whole is increased 

 by the comparison. To aid the geological reader 

 in deducing from them those general conclusions 

 which are more interesting to him than a naked col- 

 lection of topographic details, an article is subjoined 

 to each division, in which it is attempted to bring the 

 principal facts into one condensed point of view. By 

 this it is hoped that his progress through the work 

 will be facilitated, and that a small portion at least of 

 that fatigue, which is always the result of a long 

 continued statement of details, will be removed. As 

 it is not however probable that the conclusions of the 

 reader will always coincide with those of the writer, 

 there is still abundant room left for his own reflec- 

 tions. 



Lastly, in examining the general relations of the 

 different individuals of each group, it has also been 

 attempted to connect them with the adjoining main- 

 land, wherever it appeared necessary to do so for their 



