revealed a torn-up condition as though the starv- 

 ing winter inmates had dug out for food every 

 root and rootstock to be found in the bottom. 



While visiting ponds at the beginning of win- 

 ter, I have many times noticed that, shortly after 

 the pond was solidly frozen over, a hole was made 

 through the dam just below the water-surface of 

 the pond. This lowered the water-level two inches 

 or more. Did this slight lowering of the water 

 have to do with the ventilation of the ice-covered 

 pond, or was it to put a check on deep freezing, 

 or for both purposes ? 



In the majority of cases these holes were made 

 from ponds which, during the winter, received 

 but a meagre inflow of fresh water. Naturally, 

 ponds receiving a strong inflow of water would 

 be better ventilated, and would freeze less swiftly 

 and deeply than those whose waters became 

 stagnant. This drawing-off of water after a few 

 inches of ice had formed, would, in some places, 

 despite the settling of the ice, form an air blanket 

 that would delay freezing, and thus possibly pre- 

 vent the ice from forming so thickly. The air 

 admitted by drawing off the water would be in- 



202 



