viii PREFACE. 



veries of others, but simply to markeither that we have 

 made some alteration in the nomenclature of the species, 

 or that we have included under the name forms hitherto 

 regarded as distinct. 



Many of the memoirs have been admitted into the 

 ' Annals of Natural History,' but as it would occupy 

 about four years to have the remainder of them inserted 

 in that excellent work, I have determined to print the 

 whole at once in a collective form, and the Editors of 

 the ' Annals ' have liberally accorded me permission to 

 reprint those which have appeared in the pages of their 

 journal. My reason for making this arrangement is, 

 that, at my age, it would be almost presumptuous in 

 me to calculate upon being able to watch the publi- 

 cation of my observations during such a long period 

 as four years. 



I can entertain no doubt that my work is very de- 

 fective, and, on such a subject, it would still be so, if 

 I were to bestow the labour of another half century 

 upon it. Were it at all probable that I might re- 

 examine the whole matter, with the advantage of having 

 first impressions defined and corrected by intermediate 

 study, I should probably not have chosen this desultory 

 form of publication ; but if any justification of such a 

 course be required, I have at least the opinion of Pro- 

 fessor James Forbes to support me. That eminent 

 philosopher, in his excellent ' History of Norway and 

 its Glaciers,' well observes, 



"But a pretty long experience in such matters has 

 convinced me that they act wisely and well, who, having 

 used their opportunities to the best of their power, 



