55° Notices of Books. [October, 
where it might now be sought in vain. Perhaps, however, the 
decrease of our choicer native ferns may be due not so much to 
the rapacity of cultivators as to the increasing pollution of the 
atmosphere in many parts of the country. Air fraught with 
coal-smoke is very uncongenial to many ferns and mosses, and 
checks their fructification. 
In recommending this book to all who are interested in the 
study and in the cultivation of ferns, we must beg to express 
t Our sympathy with the author, who has been deprived of that 
sense which to all observers of Nature is dearer than life itself. 
Narrative of the North Polar Expedition. U.S. Ship Polaris, 
Capt, C. F. Hall commanding. Edited by Rear-Admiral 
C. H. Davis, U.S.N. Washington : Government Printing- 
Office. 
Polar exploration excites in men of different tastes and pursuits 
a widely different amount of interest. The biologist looks on 
almost with indifference, well knowing that a year’s labour in the 
far north would yield fewer results of value than might be met 
with in a single day in climates more genial. The geologist and 
mineralogist, though well aware that important portions of the 
“ great stone book ” have been, in all probability, deposited 
around the poles, still fear that accumulations of ice and snow 
may for ever hide them from human perusal. On the other hand, 
the geographer, the meteorologist, and the student of terrestrial 
physics turn their gaze northwards with eager curiosity, and will 
doubtless never desist from their endeavours to solve the mystery 
of the poles till their efforts are crowned with success, or till 
many future adventurers, like Franklin and Hall, have found a 
glorious death. Nor can the risk and the possible sacrifice be 
considered to outweigh the prize that remains to be won. 
Material benefit, indeed, is out of the question. No one now 
explores the icy regions in the hope of finding an available 
passage from Europe, or from the eastern shores of North 
America to the Pacific ; nor is the prospedt of mineral wealth a 
temptation, for though valuable ores doubtless lie hid in these 
regions, the cost and difficulty of bringing them to daylight and 
transporting them to a market would be scarcely surmountable. 
But from a speculative point of view the inducements to polar 
investigations are tempting indeed. Setting aside the extrava- 
gant dreams of earlier days, such as the notion of an aperture 
leading down to beautiful and habitable regions in the interior of 
our globe, it remains to be decided whether the poles are covered, 
according to the theories of Adhemar and others, with massive 
caps of ice miles in thickness ; whether they are, as some sup- 
pose, covered by open sea, enjoying a milder climate than the 
