LICHENS. 159 
half-a-foot in diameter ; and with its grey blisters 
rising above the dark charred-looking thallus, it 
imparted a weird aspect to the grim shores of 
that lake of Avernus. Though the Gyrophoras 
contain a considerable quantity of starch, they 
are exceedingly bitter and astringent, and pro- 
duce intolerable griping pains when eaten. No 
one would have recourse to them for food except 
in a case of dire necessity. The Canadian 
hunters, who are often reduced to the last 
extremity, during their long and toilsome excur- 
sions in search of furs, through the desolate 
regions of Arctic America, often allay the pangs 
of hunger with this nauseous diet. And some- 
times in my own wanderings among the almost 
unknown solitudes of the Scottish mountains, 
when my stock of provisions was exhausted, and 
a renewal was not to be expected, the nearest 
shepherd’s sheiling being perhaps many miles 
distant, I have been compelled to satisfy my 
cravings by eating small portions of the tripe de 
roche, which I found blackening the dreary rocks 
around. In such situations, I have felt deeply 
how weak and helpless is man, when thrown forth 
from the social scenes and comforts of civilized 
life, left to his own unaided resources, and 
exposed to the merciless energies of physical 
nature, and how, without some ultimate trust in 
