5°4 



DISCOVERY REPORTS 



APPENDIX 



A test of the validity of the continuous plankton recorder method 

 By A. C. Hardy, M.A. and Nora Ennis, B.Sc. 



In April 1929 with the kind permission of Dr E. S. Russell, Director of Fisheries 

 Investigations, Ministry of Agriculture and Fisheries, one of the authors (A.C.H.) 

 carried out trials with the modified Type I Continuous Plankton Recorder from the 

 research ship ' George Bligh ' during a cruise in the southern North Sea. The object was 

 to test several modifications in the mechanism before embarking upon the construction 

 of the first of the Type II machines. 



MILLIONS 

 60- 



60- 



40 



20 



NAVICULA 



2000000f 

 i.ooooooj 



600000-! 



400000 



200000- 



E0QO00 



100000- 



200000 



1 00000- 



300000- 

 200000- 

 1 00000- 



50000- 



50000 -| 



* 



*-— * 



* 



BACILLARIA 

 LAUDERIA 



% 



%. 



* 



* 



% 



I 2 3 4- 5 6 7 6 9 10 II 12 13 [14] 15 IB 17 [lB] 19 20 21 22 23 24 25 26 

 CONSECUTIVE INDICATOR HAULS _ I mile each 

 Fig. 28. Histograms showing the relative quantities of phytoplankton taken in consecutive samples obtained 

 with the Plankton Indicator in the North Sea on April 8th, 1929. Samples 14 and 18, indicated by asterisks, 

 were unfortunately lost before analysis. For further details see text. 



