224 THE AMERICAN BEAVER. 



stream, and with the large ends facing the current. 

 It is begun literally at the surface of the water, and 

 the first courses are sunk to the bottom by successive 

 deposits upon them. I have seen such dams when 

 first commenced, and when the brush filled but a 

 small part of the channel. 



At first the brush makes a loose dam, through 

 which the water flows without sensible obstruction; 

 but when the materials, by their increase in quantity, 

 begin to check the flow of the water and to experi- 

 ence, in consequence, an increase of pressure, they 

 commence carrying in and depositing upon them 

 earth, sods, and stones, for down-weight to anchor 

 them, as well as to fill up the interstices. The first 

 season the beavers content themselves with a low 

 dam, rising about a foot above the original level of the 

 water, and afterward raise it from year to year until 

 it reaches its natural limitations. In this manner the 

 small dams on the main branch of the Esconauba, 

 near its sources, were constructed. For several miles 

 this stream passes through comparatively level land, 

 with a channel about thirty feet wide and from one to 

 two feet deep, and with defined banks about three feet 

 high. Dams are found at short intervals upon its entire 

 course, and also upon its small tributaries; but those 

 upon the former are short, low, and inferior struc- 

 tures. Beaver meadows border this river continu- 

 ously for miles. As places of concealment, they are 

 equivalent to thousands of burrows. These meadows 

 show of themselves how completely the stream has been 

 appropriated, in past times, for beaver habitation. 



The persevering industry of beavers in repairing 

 their dams is well established. Many successive 



