ocojsroMowoc lake, etc. 33 



water is popularly believed to be much colder than that at the 

 surface. 



WIND 



The strong wind blowing over the lake causes a surface current 

 which must be balanced by a counter current below, and thus by a 

 constant interchange of Avater equalizes the temperature. If the 

 day is warm with but little wind, the surface water will become 

 the warmest; at night the surface cools down so that in the early 

 morning it is colder than at the bottom. 



The deep-water fishes do not, therefore, seek that locality on ac- 

 count of diminished temperature. 



One lake is said to have remained open nearly all winter; the 

 cold weather having been accompanied by high wind, which pre- 

 vented the water from freezing. 



When the surface is once covered with ice the currents cease, 

 and ice is formed of great depth and of crystal transparency and 

 purity. 



The temperature of the spring-water along the shores remain 

 nearly uniform throughout the year, varying from 47 to -19 degrees, 

 which is not far from the mean temperature of this locality. 



The currents caused by the wind blowing over the surface of the 

 lake, act upon the bottom and shores, causing abrasions at some 

 places and accumulations at others, very much as by the larger 

 currents of the ocean. This is quite apparent at tAvo points on the 

 channel between the lake and the large bay at the northeast angle. 

 The current flowing into the bay from the lake causes an eddy at 

 these points from which are deposited long narrow bars projecting 

 from the shore. This channel it will be seen is quite narrow and 

 the water in it shallow. 



These currents also cause accumulations of beach sand and 

 gravel at certain points along the shore; separating and assorting 

 the material upon a small scale, precisely as is done on a larger 

 scale by the currents in the great lakes, and in the ocean. 



While white shell marl is accumulating in some portions of the 

 3 w A s 



