143 



which it is built is still more astonishing than 

 its size. The part of the river over which this 

 dam is usually built is where it is most shallow, 

 and where some great tree is found growing by 

 the side of the stream. This they pitch upon 

 as proper for forming the principal part of their 

 building ; and althouglj it is often thicker than 

 a man's body, they instantly set about cutting 

 it down. For this operation they have no other 

 instrument than their teeth, which soon lay it 

 level ; and that also on the side they wish it to 

 fall, which is always across the stream. They 

 then set about cutting off the top branches, to 

 make it lie close and even, and serve as the 

 principal beam of their fabric.* 



This dyke or causeway, is sometimes ten and 

 sometimes twelve feet thick at the foundation. 

 It descends in a declivity, or slope, on that side 

 next the water, which gravitates upon the work 

 in proportion to the height, and presses it with 

 a prodigious force towards the earth. The op- 

 posite side is erected perpendicular, like our 

 walls ; and that declivity, which, at the bottom, 

 or basis, h about twelve feet broad, diminishes 

 towards the top, where it is no more than two 

 * Spectacle de la Nature. 



