vill 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. “as 
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 1s, 
that, at my age, it would be almost presumptuous m 
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 them power, 
