176 THE AMERICAN BEAVER. 



an assortment of them, some of which measure three 

 and a half inches in length, from an inch to an inch 

 and a half in width, and about a quarter of an inch 

 in thickness. 



Fig. 20. 



Beaver Chip. Natural size. 



The above representation (Fig. 20) shows the inner 

 face of one of these chips. Upon the end to the right 

 are six distinct cuts, the first two of which are but half 

 the width of a single tooth ; while on the other, which 

 is the thickest end, there are eight, some of which are, 

 in like manner, but half the width of a single tooth. It 

 is made evident by running the inferior incisive teeth 

 in a beaver's skull over these several cuts, that the 

 upper incisors are used for holding, while the cutting 

 is done by the inferior; and more than this, that but 

 a single tooth is used at a time, the other following 

 in the space made by the previous bite. There is 

 another fact which tends to confirm this explanation 

 of the manner of cutting, which is that the chip is 

 split inward toward the centre with each cut. If 

 both of the inferior incisors were cutting at the same 

 time, the split would occur with each alternate cut; 

 otherwise one of the teeth would be sprung. These 

 chips also show that the gnawing process is one of 

 splitting as well as cutting. The crowning surface of 



