North Sea, the Cattegat and the Skagerack. In 1893 and 1894 other 

 countries partook in this investigation and at the Stockholm Con- 

 ference 1899 these seasonal cruises were put as chief article on the 

 hydrographic program of research. 



A general view of the Atlantic surface-water, its salinity, tem- 

 perature and plankton-life was obtained in 1897—1898 by monthly 

 observations 1 . 



The synoptic method is valuable and necessary because through 

 it we- trace and locate the relationship of different groups of pheno- 

 mena, such as f. inst. the relationship of plankton- and fishlife to 

 the salinity, temperature and movement of the sea. This fact is 

 accentuated by the recommendation for the future reconnoitering 

 of the Atlantic of the three Geographical Congresses: of London, 

 Berlin and of Rome, and also by being taken up by the Austrian — 

 Italian investigation of the Adriatic whose program is based on the 

 pattern of the Stockholm Conference. It is all the more deplorable 

 that the seasonal cruises of the international Investigation have been 

 discontinued and that we have fallen back on a pedantic computation 

 of averages from observation-series far too defective to serve this pur- 

 pose. Fortunately the fish-biologic investigation which is carried 

 on in a less abstract manner has given so brilliant results that they 

 make up for the want of general interest in certain other fields 

 of research. 



From the beginning the oceanic periodicity and its causes has 

 been the problem of greatest interest to Swedish investigators. As 

 has been shown the cause of our present periodic phenomenen, the 

 moonwaves, is cosmic and must be ascribed to the changes in the 

 lunar constellations. Recent observations made by the Danish Com- 

 mission with the »Tor» and by the Michael Sars Expedition to the 



Strait of Gibraltar in 1910 show that waves similar to those we found 

 in the Belt and Skagerak, though far greater, appear on the sub- 

 oceanic ridges: the Wyviile Thomson ridge, the Faroe-Shetland a. o. 



They may be regarded as breakers of the oceanic tidal wave 

 impinging on submarine ridges. Their amplitude is very great and they 

 make the interchange of water between the Atlantic basins pulsate 

 in accord with the periods of the tidal wave. The submarine breakers 

 which enter into the Cattegat are forced to dissolve into irregular 

 eddies when the deep-channel shoals out, as at Anholt, or changes 

 into narrow grooves as in lat. 57°10 / , Here the border-layer in 

 which they travel thins out when meeting the solid seabottom. When 

 General Carp denies the existence of the moon-waves, because 

 they were not found in South Cattegat (and the Baltic!) he expects 

 too much from the transmitting power of the tidal phenomenon. 

 The localities where they can be observed are probably restricted 

 to Skagen, the Gullmarfjord and possibly the Christiania-fjord though 

 as yet we know nothing of the latter. They are only to be found 

 where the water is deep and stratified. In front of the great sub- 

 marine ridges they dissolve into breakers in the manner of surface- 

 waves. The herring-shoals travelling with thesecascades generally 

 stop fit the point in the Cattegat where the wave-motion breaks up. 

 Sometimes, if the undercurrent is very intense, the herring may pass 

 across the south plateau of the Cattegat and will then collect in 

 the sounds where the different current-branches unite. Later it 

 will be shown that this must have happened in the centuries 1,100 — 

 1,600 a. C. when the great Hanseatic herringfishery flourished and 

 the maximum of the tidegenerating force occurred. Of this lucra- 

 tive fishery only faint traces now remain in the years of good fishery 

 on the coast of Scania and in the Belt. 



II. 



Outbursts of polar ice from Arctic and Antarctic Seas. 



Submarine waves also enter the polar basin. They were first 

 traced by Nansen, who at a depth of some hundred meters found 

 irregular variations in the temperature of the Gulfstream branch 

 which enters the Polar Sea. In periods of maxima this influx will 

 be stronger and able to break up the ice, the effects of which will 

 be seen in an increase of the ice transported by the polar current. 

 In periods of minima the ice, no longer subject to the melting influence 

 of the undercurrent will increase in thickness by the cooling from 

 the atmosphere w T hich very slowly penetrates the icecover. It is 

 a wellknown fact that »outbursts» of drift-ice fom the polar seas 

 occur periodically and it is significant that the last great outburst 

 from the Antarctic which culminated in 1894 — 1895 occurred under 

 the constellation I have described as »perihelion-apside» (fig. 10). 



The following charts illustrate this great outburst of antarctic 

 icebergs. In 1888 no icebergs were reported by the Australian liners. 

 In the following years icebergs were sighted more and more frequently 



Fig. 11. Icebergs in the antarctic ocean. 

 The charts are compiled from H. C. Russels paper (Proc. R. Soc. Nw S. Wales 1896. The Signs A A denote groups of icebergs sighted. 



1 O. T. Cleve, G. Ekman and O. Pettersson: Les variations annuelles de l'eau de l'ocean Atlantique. Goteborg 1901. 



— 6 — 



