132 



THE AMERICAN MIDLAND NATURALIST 



boat. The turbidimiter was lowered in a horizontal position and 

 the depth at which it entirely disappeared from view was noted. 

 It was then slowly raised again and the depth at which it reappear- 

 ed noted. The mean of these two measurements was taken as 

 the depth of its visibility beneath the surface. This turbidimiter 

 was used at each station. 



For collecting 'purposes towing nets, made of fine silk bolting- 

 cloth were used. These nets were i8 inches long and conical, the 

 base or entrance being 8 inches in diameter and held open by a 

 wooden hoop. Three cords were attached by the same method 

 used on the turbidimiter. The apex or outlet of the net was ^ inch 

 in diameter and to this end was tied a small vial 2 inches long and 

 14. inch in diameter. On the neck of each vial there was a flange 

 which facilitated the tying on of the net. Fifteen of these collecting 

 vials were used on each trip and were carried in a box specially made 

 for them. New corks were always used and at each station the date, 

 number of towing, and a letter representing the kind of towing was 

 written with water proof ink on each cork which was then inserted 

 into a corresponding vial. See chart number i for method of 

 keeping this data. 



Field notes were kept in a water-proof covered notebook and 

 the form on the following page was used in recording observations 

 at each station. 



Date.. ., 1916. Time of day Air temperature 



Wind: Direction Velocity Water Temperature: Surface 



K distance to bottom Bottom Sky Tur- 

 bidity Carbon dioxide per 1000 c. c. Bottom condition 



The followirg terms were; used for d'^^scription ot : 



Wind. Sky. 



Not perceptible N. P. Clear CI. 



Calm C. Hazy H. 



Moderate M. Cloudy , Cd. 



Light Breeze. L. B. Foggy F. 



Strong Breeze S. B. 



Plant Life 



Abundant A. 



Sparse ...S. 



Absent Abs. 



Character of Botiom. 



Sandy Sn. 



Mucky.... .My. 



Clayey ..Cly. 



On each trip it was necessary for one man to row the boat and 

 keep notes while the other made the ol serrations. To avoid 



