263 



In this method the question of coefficient is entirely eliminated. 



The results of these tests are given in the preceding table. 



The variation in the coefficient w^ith different seasons, lo- 

 calities, and planktons is apparent upon the first glance at 

 the table. The greater straining capacity of a new net as com- 

 pared with one which had been used for some time may be seen 

 in the tests made June 16, and July 9, 11, and 21, 1896. The 

 new net — the silk in which had been shrunken by washing and 

 pressing several times prior to use — catches at least 50 per cent, 

 more than the old one which had done service since February 25. 



The rise in the coefficient as the net progressively clogs 

 by plankton is demonstrated by the tests of October 14, 1899, 

 and July 27, 1897. The latter test is graphically presented in 

 the accompanying figure. 



l^ 10 5 0-m. 



Fig. B. — Catches of plankton made on 30-meter haul by drawn net and pump 

 The upper, continuous line represents the pump catch; the middle, dotted line the 

 catch of the net measured by the settling method; the lower, heavy line the same 

 measured by the centrifuge. 



