82 



Types of Aquatic Environment 



minute icicles are forming and their tips are being broken 

 off by the oscillations of the current. These broken 

 tips constitute 

 the rubble. 

 They are some- 

 times remark- 

 ably uniform in 

 size— those form- 

 ing when this 

 picture was 

 taken were 

 about the size 

 of peas — and 

 though small 

 they are the 

 tools with which 

 the current does 

 its winter clean- 

 ing. In the 

 ponds formed by 

 damming rapid 

 streams this rub- 

 ble accumulates 

 under the solid 

 ice. 



"Anchor ice" 

 forms in the 

 beds of rapid 

 streams, and 

 adds another 

 peril to their in- 

 habitants. The 

 water, cooled 

 below the freez- 

 ing point by con- 

 tact with the air, 



.«Uit ii.ik^c 





Fig. 23. The ice veil on Triphammer Falls, Cornell 

 University Campus. The fall is at the left, the 

 Laboratory of Hydraulic Engineering at the right 

 in the picture, the only open water seen is in the 

 foaming pool at the foot of the fall. 



