BEAVER — CANALS. 
381 
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 c 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 
