THE BEAVERS OF NORTH AMERICA 17 
spring when softened by the thaw, and the heavy 
rains wash it off, leaving the outside an untidy 
mound of sticks and poles. In evidence of this I 
have made photographs both in Newfoundland and 
Canada. Some of the houses found in the former 
country were made almost entirely of mud, sod, 
and grass, with only a few sticks used in the centre, 
probably with the idea of leaving the almost 
inevitable ventilation flue. The form of the lodges 
varies greatly and it is impossible to lay down any 
hard and fast rules. Several times I have found 
houses built surrounding a tree, either living or 
dead. In such cases the ventilation is afforded by 
the tree, as the earth and sticks do not adhere very 
closely to the rough bark. The very idea of making 
provisions for ventilation is one of the many 
exhibitions of the clever animals’ thoughtfulness. 
The existence of these ventilation flues has some- 
times been questioned, but it has been more or less 
clearly shown in all of the many scores of lodges 
which I have examined. It is even more notice- 
able in the winter, when the lodge appears as a 
mound of snow, a mound like many other irregu- 
larities in the landscape except that the snow is 
usually melted or partly melted at the highest point, 
and on very cold days a thin misty vapour may be 
seen rising from the place where the flue would 
naturally be situated. This tell-tale sign is a 
frequent cause of disaster for the beaver, as it 
reveals the presence of the lodge to the keen-eyed 
R.B. c 
