and perhaps one hundred feet above, trickled 

 down and in due time formed a pond. The fol- 

 lowing year this pond was enlarged, and an- 

 other one built upon a terrace about one hun- 

 dred feet up the slope. From year to year there 

 were enlargements of the old pond and the build- 

 ing of new pondlets, until there were seven on 

 the terraces of this moraine. These, together 

 with the connecting slides and canals, required 

 more water than the spring supplied, especially 

 in the autumn when the beaver were floating 

 their winter supplies from pond to pond. Within 

 the colony area, too, were many water-filled un- 

 derground passages or subway tunnels. One of 

 these penetrated the turf beneath the willows for 

 more than two hundred feet. 



While watching the autumnal activities of this 

 colony, as described in another chapter, I broke 

 through the surface and plunged my leg into an 

 underground channel or subway that .was half 

 filled with water. Taking pains to trace this 

 stream downward, I found that it emptied into 

 the uppermost of the ponds along with the waters 

 from a small spring. Then, tracing the channel 



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