LEVELS AND TEMPERATURE OF LAKE OKOBOJI 91 



RECORDS OF OSCILLATIONS IN LAKE LEVEL AND 

 RECORDS OF LAKE TEMPERATURE, AND OF 

 METEOROLOGY, SECURED AT THE MACBRIDE 

 LAKESIDE LABORATORY, LAKE OKOBOJI, IOWA. 

 JULY, 1915. 



JOHN L. TILTON. 



At the Macbride Lakeside Laboratory, Milford, Iowa, the 

 writer began a series of observations last summer (1915) for his 

 own information to ascertain what the fluctuations were in the 

 level of the lake, and to determine the relative value of the 

 causes that operated to produce those fluctuations. It soon be- 

 came evident that the records sought were desired also by teach- 

 ers in other departments because of the bearing of such data on 

 life zones and conditions in the lake. Since then the government 

 has called for all data available on evaporation in Iowa. The 

 data are therefore here presented that they may be of immedi- 

 ate use and on file for future reference. 



To detect the oscillations in the level of the lake it first be- 

 came necessary to devise a piece of apparatus for that purpose. 

 A closed hollow cylinder two inches in diameter was placed as a 

 float in a larger cylinder three inches in diameter, closed at 

 the bottom. Through the sides of this outside tube a few nail- 

 holes were punched to let in the water slowly so that the 

 float inside of this tube would rise and fall gradually but not 

 move perceptibly for small waves. This was placed in a vertical 

 position in the water close to the boathouse where the water 

 was about four feet deep. It was found that waves five or six 

 feet from crest to crest and perhaps a foot from trough to 

 crest would move the float about the twentieth of an inch. When 

 a steamer made a landing the float would rise and fall about 

 three-eights of an inch. To an upright rod fastened to the float a 

 thin strip of brass was attached, on the end of which was a pen 

 which traced all vertical movements on a cylinder that revolved 

 once a week by clock work. The revolving cylinder, the pen 

 and penholder, were parts of a thermograph which was thus 

 made to serve present purposes. 



