BEAVER CANALS. 



581 



ground, and throughout this distance, being level with 

 the pond, it is supplied with water from this source. 

 Where the rise begins a dam is made, and the canal is 

 then continued for 25 feet at a level of one foot 

 higher than before. This higher level reach is supplied 

 with water collected from still higher levels by another 

 dam, extending for 75 feet 'upon one side of the 

 canal and 25 feet on the other, in the form of a 

 crescent with its concavity directed towards the high- 

 lands, so as to collect all the drainage water, and concen- 



trate it into the second reach of the canal. Beyond this 

 larger dam there is another abrupt rise of a foot, and the 

 canal is there continued for 47 feet more, where a third 

 dam is built resembling the second in construction, only 

 having a still wider span on either side of the canal (142 

 feet), so as to catch a still larger quantity of drainage 

 water to supply the third or uppermost reach of the canal. 

 We have, therefore, here presented, not only a perfect 

 application of the principle of ' locks,' which are used in 

 canals of human construction, but also the principle of 

 collecting water to supply the reaches situated on the 

 slope by means of elaborately constructed dams of wide 



