GASES IN WATERS OF WISCONSIN LAKES. 



1283 



GASES AND CARBONATES OF OTHER LAKES IN SOUTHEASTERN WISCONSIN. 



We may contrast the summer conditions in Lake Mendota with those that 

 obtain in the deepest inland body of water in Wisconsin, Green Lake. This 

 has a maximum depth of 72 meters, with length of about 12 kilometers and a 

 breadth of 4 kilometers. Figure 1 2 shows the conditions found in Green Lake 

 on October 4, 1906. The volume of water is so great that summer conditions 

 of temperature still remain, and cooling has proceeded to no great depth. The 

 water shows the characteristic summer condition of an alkaline upper stratum, 



Fig. 9. — Lake Mendota, August r, 1906. 



with the cooler water acid. The dissolved carbonates are low in the warmer 

 waters, rapidly increasing at the thermocline, and then remaining nearly con- 

 stant till the bottom of the lake is almost reached, where there is again an 

 increase. The oxygen shows a marked diminution in the thermocline (ii 

 meters to 1 6 meters) ; it then slowly increases in quantity with the depth until 

 a maximum is reached at about 40 meters, which remains for some 10 meters; 

 and the amount of the gas then declines until it is nearly or quite exhausted at 

 the bottom. The diagram shows plainly the effect of life and death on the 

 oxygen where it is found in abundance in a large voltune of water. The oxygen 



