46 Roosevelt Wild Life Bulletin 



down into contact with the bottom mud, the higher temperature of 

 the latter had been sufficient to mek it somewhat. This was shown 

 not onh- by the fact that the ice here was about three-fourths of an 

 inch thinner than on most parts of the drained bottom but also by 

 the spongy texture and the impressions of leaves, twigs, etc., which 

 characterized its lower surface. The bottom here, and to a less 

 degree in other shallow coves and basins, is a nearly black muck 

 filled with organic matter, the slow oxidation of which probably frees 

 a perceptible quantity of heat. It was also determined, especially in 

 the neighborhood of Globe and Brooklyn Industrial Camps that 

 much ground water from both exposed and subaqueous springs was 

 draining into these basins, the effect of which was to maintain a 

 higher temperature of the bottom even after exposure. 



Comparing the existing conditions with those postulated in the 

 recommendation of September 14 it will be seen that the temperature 

 of the bottom mud instead of being — 6" C. (21" F.j as desired was 

 about 10° C. (18° F.) warmer. While the air temperature had been 

 sufficiently low to effect the desired result under favorable condi- 

 tions it seems e^■ident that three factors were operating to prevent it. 

 First, the hea\y and continuing blanket of snow acted as an insulator 

 against the rapid radiation and conduction of ground heat; second, 

 the effects of the cold were greatly mitigated by the constant and 

 abundant flow of warmer ground water beneath the ice and snow 

 cover ; and, third, the slow decomposition of abundant organic matter 

 in certain places freed sufficient heat to somewhat elevate the 

 temperature. The effect of the first two conditions, if realized, were 

 anticipated and referred to in the memorandimi ; the possibility of the 

 third, though obvious enough, was overlooked. 



Concerning possible remedies it is obvious that corrective measures 

 on a scale sufficiently large to be of much value could scarcely be 

 taken against conditions i and 3. For experimental purposes it would 

 be practicable to keep limited areas free of snow, especially by the 

 use of a horse plow on the coves at Globe Camp and Herbert's. But 

 the effects of 2 might be mitigated by further lowering the water 

 level. This would expose a larger surface of the bottom to loss of 

 heat, drain off the warmer ground waters from the flats more effec- 

 tually, and remove the A\-intering areas of the greater number of the 

 leeches farther from the tempering influence of the body of water 

 of the lake. Accordingly, it was recommended to ]Mr. Welch that 

 the ^^•ater be lowered an additional eighteen inches as soon as 

 practicable. This would bring it to a point three inches lower than 

 had been proposed originally. 



The search for the leeches in their winter quarters was handi- 

 capped by the h&axx covering of snow and ice, but thanks to the 

 efforts of two men furnished by ]Mr. Welch a quantity of the mud 

 from the bottom of the Cove near Herbert's ^s-as shoveled on to the 

 ice and examined. Two leeches only were found, one each of 

 Macrobdclla decora and Erpohdella punctata, both alive and dormant. 



The winter of 1919-20 proved to be a long and severe one, with 



