THE OBSERVATIONS OF AIR AND SEA MOTIONS. 21 



represents the isobaric sheet IX, the single lines giving the absolute topography 

 of the 900 m-bar surface and the double lines the relative topography of the 800 

 m-bar surface, and so on. 



On the charts representing thus the different isobaric sheets, we now introduce 

 the arrows and corresponding numbers representing the air-velocities given in table 

 D. These data regarding the air-motions in the higher strata, in connection with 

 the corresponding data for the ground which are given on plate LIU, will now form 

 the basis for the further diagnostic work regarding the air-motion above central 

 Europe, July 25, 1907, about 7 a. m. Greenwich. 



108. On the Observations of the Sea-Motions. If the observations of the air- 

 motions are too scarce, this is still more the case with those of oceanic motions. 

 Quantitative measurements are only to be had exceptionally. The motions of the 

 sea's surface is in many cases known qualitatively from the drift of floating objects 

 or of bottles thrown out for the purpose of investigation. Qualitative conclusions 

 as to the motions in the deeper sheets can be drawn from the measurements of 

 the salinity, this giving information as to the origin of the waters. Similar conclu- 

 sions can be made also on the basis of the examination of the organisms contained 

 in the water. But none of these observations are of the quantitative nature which 

 can give rise to a closer kinematic analysis. 



For this reason we can work out no example of a kinematic diagnosis of the 

 sea-motions. But the principle of the methods to be employed in the case of the 

 sea, as soon as serviceable material of observations is produced, will be sufficiently 

 illustrated by the example worked out for the case of the atmosphere. We shall 

 therefore only make occasional references to the sea. 



The most important point to emphasize is the necessity of producing sufficient 

 data of direct observations of the sea-motions from the surface as well as from all 

 depths. Suitable instruments for doing it have already been invented.* It remains 

 only to bring them into application on a sufficiently large scale and according to 

 rational principles. 



*V. W. Ekman: Kurze Beschreibung eines Propell-Strommessers. Conseil Permanent International pour 

 l'Exploration de la Mer. Publications de Circonstance No. 24. Copenhague, 1905. 



Otto Pettersson: Beschreibung des Bifilarstrommessers. Publications de Circonstance No. 25, Copenhague, 1905. 



A. M. van Roosendaal und C. H. Wind: Prtifung von Strommessern und Strommessungsversuche in der Nordsee. 

 Publications de Circonstance No. 26. Copenhague, 1905. 



Fridtjof Nansen: Methods for measuring Direction and Velocity of Currents in the Sea. With an Appendix by 

 V. W. Ekman: Current Measurements by means of buoy and releasing clock-work. Publications de Circonstance 

 No. 34. Copenhague, 1906. 



Helland-Hansen: Current Measurements in Norwegian fjords, the Norwegian Sea, and the North Sea in 1906. 

 Bergens Museums Aarbog No. 15. Bergen, 1907. 



Otto Pettersson: Stromstudier vid Ostersjons portar. Svenska hydrografisk-biologiska Kommissionens, Skrifter 

 III. Gotenburg, 1908. 



B. Helland-Hansen and Fridtjof Nansen: The Norwegian Sea. Report on Norwegian fishery and marine 

 investigations, Vol. II, No. 2. Christiania, 1909. 







