CHRISTIANIA, 1901. 401 



The same standard sea-water* shall be employed in all cases for 

 standardising the solutions used for chlorine determinations. 



The chemical analysis shall be controlled by physical methods, and 

 the physical determinations by chemical analysis in the following 

 manner: From every collection of samples examined at least three 

 shall be selected and sent to the Central Bureau. Standard samples 

 shall be sent in return. 



V. 



§ 11. Samples for gas analysis are to be collected in duplicate iu 

 sterilised vacuum tubes. 



It is desirable that the existing tables of absorption of nitrogen and 

 oxygen shall be revised. 



VI. 



§ 12. Qualitative plankton samples should be taken as frequently as 

 possible from the surface by approximate methods simultaneously with 

 the water samples, and also from deeper layers at the stations referred 

 to in § 2 (see below, B. VI., § 12). 



I 13. Observations of the transparency and colour of the water 

 should, when possible, be made at the same points. 



VII. 



§ 14. Observations on currents and tides should be carried out as 

 frequently as the circumstances allow. 



The currents should be examined, when possible, by direct current- 

 meters, and by surface and intermediate floats, and by bottom-rollers. 



The ship should be anchored occasionally in order to make frequent 

 observations during a complete period of tide. 



VIII. 



§ 15. It is desirable that a chart should be prepared, showing the 

 nature of the deposits on the sea-bottom. 



The description of the deposits is to be carried out on a definite plan, 

 to be afterwards settled by the Central Bureau. 



IX. 



§ 16. The normal observations are to be carried out along the lines 

 provisionally drawn on the annexed chart, where R denotes the Russian, 

 F the Finnish, *S' the Swedish, G the German, Da the Danish, Dn the 

 Dutch, N the Norwegian, and B the British lines ; but the Central 



* By standard Avater shall be understood samples of filtered sea-water, tlie 

 physical and chemical properties of which have been determined with all possible 

 accuracy by analysis, and statements of which are sent to the different laboratories, 

 together with samples. 



