502 DISCOVERY REPORTS 



ACKNOWLEDGEMENTS 



There are many people to whom I am indebted for help in the development of the 

 Continuous Plankton Recorder. First and foremost I wish to express my great sense of 

 gratitude to Dr Kemp, who gave such sympathetic support to the initiation of the 

 project, followed by never-failing encouragement during the often disappointing trials 

 of the first machine, and to the Discovery Committee who so generously made possible 

 the realization of the idea. 



The working drawings of the original Type I machine were prepared from my 

 sketches by Mr M. T. Denne, who made a number of valuable suggestions regarding 

 the details of construction. The working drawings for the Type II machine were made 

 by Messrs R. W. Munro, Ltd., of South Tottenham, London, who have built all the 

 machines to date and to whom I am also indebted for suggestions as to methods of 



construction. 



I have already recounted how the system of diving planes I had designed from 

 experiments with models failed to give stability to the full-sized machine. The con- 

 version of this failure to success I owe to the kindness of the Officer Commanding the 

 Department of Mine Design, H.M.S. 'Vernon', Portsmouth, and his staff, who carried 

 out stability tests, designed the present system of planes and weighting of the machine, 

 and furnished me with the data regarding the depth to which it will descend for a given 

 length of towing rope. 



During the 1925-7 voyage of the ' Discovery ' much of the successful performance of 

 the first machine was due to the mechanical skill of my former colleague, Mr H. F. P. 

 Herdman, who performed many an operation on its internal mechanism to improve 

 its working. Similarly at Hull in the running of the Type II machine and its improved 

 efficiency in the field we owe much to the mechanical knowledge of our present colleague, 

 Dr G. T. D. Henderson. 



The excellent drawings of the machine which illustrate the present report have been 

 made by Messrs Garrett and Campbell, Ltd., 88 Chancery Lane, London, W.C. 2. 



SUMMARY 

 The Continuous Plankton Recorder has two main functions : firstly, it enables one to 

 study in detail the changes in the abundance of different plankton organisms along a 

 continuous line of observation through the sea, and secondly, if several are used 

 simultaneously they enable one to carry out broad periodic surveys using commercial 

 ships. It renders possible the introduction of meteorological-like methods into the 

 treatment of planktological problems concerning wide areas of sea. Other uses are 



discussed. 



The instrument is provided with diving planes and, when towed like a paravane 

 behind a ship at the required depth, continually samples the plankton in the water 

 traversed. A propeller turned by the passing water causes a long banding of gauze to be 

 wound across a flow of water through the machine, where it sieves out the plankton ; 

 immediately after leaving the water tunnel this gauze banding is joined by another so 



