Depth and Temperature of Green Lake. 



217 



I have made no attempt at systematic soundings, but, in connection 

 with dredging, have always taken the depth at the time of the haul, and 

 my figures agree in all respects with those of Prof. Kenaston, except 

 that they are uniformly somewhat less; this is easily explained by the fact 

 that the level of the lake has been lower than usual for the past two or 

 three years. 



In the western part of the lake but few soundings have been made by 

 any one. Capt. Pierce tells me that the greatest depth he has found is 

 172 feet. It is popularly supposed that the deepest place is between 

 Sugar Loaf and the south shore, as that is the last place to freeze. I 

 have found there, however, only 189 feet. 



It will be noticed that the littoral zone, in most parts of the lake, is 

 very narrow, considerable depths being reached quite near the shore. 



When dredging in deep water, I also took surface and bottom tem- 

 peratures. This work was done in Aug., Sept., and Oct. 1890, and July, 

 1891. As, so far as I know, very little work of this kind has been done 

 in our lakes, I have thought the results worth recording, although my 

 observations were too few to form a basis for any general inferences. 



For bottom temperatures, I used a Miller-Casella deep sea thermom- 

 eter, loaned by the United States Commissioner of Fish and Fisheries, 

 and for surface temperatures a common chemical thermometer. As the 

 thermometers were not tested, the results may not be absolutely accur- 

 ate. The deep sea thermometer was attached about two meters from the 

 sounding lead, giving the " bottom temperature." 



The following tables give the temperatures arranged by depths: 



August, 1890. 



Depth. 



Surface tern. 



Bottom tern. 



17 meters. 



25° C. 



10.25° C. 



24.5 



25. 



7.7 



31. 



26. 



7.45 



33. 



24. 



7.2 



36. 



25.5 



7.2 



40.5 



26. 



7. 



40.85 



25. 



7. 



41.5 



24. 



7. 



42. 



24.5 



rr 



i. 



42.2 



24. 



7. 



43. 



24. 



7. 



45.25 



46.75 





6.6 

 6.6 



24. 



48.45 



22. 



6.6 



