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 



