267 



point of collection the run of driftwood in the stream exhibited 

 no marked difference in current in the channel for an extent 

 of fully 400 feet. Approximately uniform conditions thus pre- 

 vail over a considerable extent of the river channel at this 

 point. At high water (PI. III. ) the banks are submerged, but 

 aside from increased rapidity and some lateral extension there 

 is no noticeable difference in the conditions of the current. 



MODIFICATIONS OF METHODS AT THIS STATION. 



Collections made by the oblique-haul method were always 

 taken on the western side of the stream, across the current 

 from a point in deep water, the surface end of the haul being 

 completed in shoaler water. At times of high water it was 

 necessary, both on account of the strength of the current 

 and the depth, to shift the apparatus still more towards the 

 shore, and, finally, in the flood of December, 1895, to abandon 

 the method and substitute temporarily a series of four to six 

 vertical hauls, amounting to about 30 meters — the usual dis- 

 tance of the oblique haul. These were made in midstream 

 from a floating or anchored boat, and were continued from De- 

 cember 27, 1895, to May 20, 1896. After the adoption of the 

 pumping method on the latter date the boat or launch was at 

 first allowed to drift with the current while the collection was 

 made. Owing to frequent difficulty caused by the drifting of 

 the boat into shallow water by the wind before the catch was 

 completed, we finally adopted the plan of anchoring the boat 

 or launch in or near the mid-channel while the collections were 

 being made. 



During the winter season, owing to air-holes and weak 

 places caused by the irregular melting of the ice upon the low- 

 er surface, the ice on the river channel was rarely firm enough 

 to permit safe transit of our plankton outfit, whose total 

 weight was over 800 pounds. Steel runners were placed upon 

 the bottom of the boat, and by the aid of ice hooks it was pos- 

 sible to run over or to break one's way through thin or 

 rotten ice to the mid-channel station, where open stretches of 



