COUNCIL - MARCH 1920 - APPENDIX — 66 ^ 



It is recommended that all surface routes to be sampled by each country- 

 be specified in the Hydrographical Resolutions, that the countries concerned should 

 send duplicate copies of all observations to the Bureau for permanent record, 

 that the Bureau should publish in the Hydrographical Bulletin a precis of the 

 number of samples received for each route, and that the Bureau should be recom- 

 mended to prepare for each International Meeting a summary showing the extent 

 to which each resolution has been carried out by each participating country. 



It is submitted that the presentation of the surface data in the form of 

 monthly charts in the Hydrographical Bulletin is a matter for discussion. 



(Signed) E. C. Jee. 



Appendix II. 



Hydrographical Memorandum for consideration at Hydrographical Section, 



International Council, 1920. 



Current Measurements. 



In considering the results of Mr. Edser's Statistical examination of certain 

 current measurements appended hereto the following factors must be reviewed: — 



The instruments used and their probable errors of measurement; the nature 

 of the observers; the conditions under which the instruments were employed; the 

 nature of the sea area in which the observations were made. 



The instruments employed on the English line were Ekman Meters; on 

 Lightships the Jacobsen Meter was used. Both meters are fair weather instruments 

 and cannot be employed in rough weather. It would be quite impossible to ensure 

 hourly observations except in fair weather and probably few observations could 

 be taken just when they would be most valuable i. e., in the winter months. 



All Ekman Meter observations were taken by skilled observers. The smoothing 

 necessary to get tidal ellipses must therefore be attributed to unperiodic swirls 

 of water influenced by meter experimental errors and the motion of the vessel. 

 The Jacobsen meter observations on the other hand have all been undertaken 

 by Lightship crews and although every precaution has been taken to inform the 

 observers fully of the method to be employed by demonstration on board ship 

 and by supervision of the installation of the meter, errors have undoubtedly crept 

 in which has necessitated extensive smoothing of the observations. It is impossible 

 to gauge the influence of this smoothing on the magnitude of the resultant current. 



According to the salinity observations in the English Channel the Atlantic 

 water normally makes its influence most felt in November or December. It is there- 

 fore at this period that current measurements are most needed to measure the 

 influx into the Southern North Sea of high salinity water. With Ekman or Jacobsen 

 Meters it would be impossible to undertake the collection of the necessary data. 



