9 



On PI. 4, will be seen two hydrographical sections made in 

 the middle of May 1896 and 1897, on board the cruiser "Heimdal". 

 Both were made on the same line from about 61 N. lat., 4 E. 

 long., to 67 N. lat., 8 W. long. The difference between the two 

 is perceptible. In 1896, the Gulf Stream was twice as broad on 

 the surface as in 1897, and, in the deep, it is met with on great 

 areas beneath the shallow Polar current at a depth of 100 to 150 

 metres. In 1897, on the other hand, the Polar current is at least 

 200 metres in depth, down as far as 64 N. lat., on the meridian 

 of Greenwich. The consequence of this was, that the temperature 

 throughout, was 2 lower in 1897 than in 1896. 



Comparisons shew that the condititions can vary greatly at 

 like seasons in different years. The cause of this may be due 

 to the derangement of the seasons, or also to the Gulf Stream 

 and Polar current not having a like development in different years. 



Several points favour the latter hypothesis. If one lays down 

 the track of the "Heimdal" in May 1897, on the chart for March 

 of that year, it will be seen that the boundary of the Polar cur- 

 rent on that line is pretty well unchanged between March and May. 

 On the other hand, it may happen in certain years that the surface 

 temperature in March, can be so distributed that the Heimdal line 

 could be marked down to represent it. 



Professor Mom? has been so kind as to allow us to make use 

 of the original observations from which he constructed his Chart of 

 Temperature for March. It appears that in some years, for instance 

 1867, that the 5 curve of temperature, which may be looked upon 

 as the boundary of the Atlantic water, makes a great turn towards 

 the northwest, in the direction of Jan Mayen, up to 63 N. lat., 

 5 W. long., and that the 8 curve can pass many miles to the 

 north east of the Shetlands (for instance in 1867, 1883). 



It thus appears as if the Polar current were differently deve- 

 loped in different winters, and in 1897, it seems to have been of 

 an unusually great thickness. This is also confirmed by comparing 

 the curves of temperature on PI. 3, with MOHN'S Chart of Tempe- 

 rature for March [87, pi. XXVIII], which was constructed on the 

 average temperature from the observations of 19 years (1867 85). 



In the southern portion of the Northern Ocean the curves 

 (especially those for 3, 4 and 5), in 1897, are further towards 

 the south and east than in average years, but as a counterbalance 

 to this, unusually high temperatures will be found along the south 

 coast of Iceland. 



The ice-conditions too, can, according to RTDEB'S investigations 

 vary greatly from one year to the other*). 



As will be seen from the Danish Ice Charts, the boundary of 

 the ice remains somewhat unchanged throughout the months of 

 March, April and May. RYDEB likewise states [96, p. 24] "The 

 boundary of the ice, under the influence of prevailing winds may 

 change, somewhat, backwards and forwards, but, in the main, retains 



*) RTDEB [96]. See also the Reports of the Danish Meteorological Insti- 

 tute on the Ice-conditions in the waters east of Greenland, and in Davis Straits 

 [189397]. 



its position until the end of May. On the other hand, in June, 

 the boundary of the ice commences to retire in a westerly direc- 

 tion with a growing speed, which increases very considerably in 

 July and August." 



We have above shewn that also the distribution of the layers 

 probably remains somewhat unaltered from March to May. 



If now a comparison is made between the spread of the ice, 

 and the conditions of the current in the spring of the two years 

 1896 and 1897, it will be seen that there was more ice to the 

 north and east of Iceland in 1896 than in 1897, which was an 

 unusually open (ice-free) year. In 1883, when the conditions of 

 the current were somewhat similar to those of 1896, there was 

 likewise much ice. 



From the results already obtained, it thus appears that the 

 Polar current, east of Iceland, is strongest .in those years when 

 there is least ice in those parts. But it must be left to future 

 investigations to discover the regular connection between those 

 phenomena, 



In their latest report [98], PETTEESSON and EKMAN give an 

 account of some observations on the distribution of the Gulf Stream, 

 between Spitzbergen and Norway, during the summers of 1896 and 

 1897. They have discovered that the Gulf Stream, in those parts, 

 was unusually thick in 1897; while in 1896 it did not extend so 

 far, but, nevertheless, still further than noted in the observations of 

 the Northern Ocean Expedition during 1876 78. 



Whilst thus, in 1897, the Atlantic water, between Iceland and 

 Norway, had withdrawn unusually far back until the first half of 

 May, in the latter days of the same month it was of unusual 

 thickness between Norway and Spitzbergen. 



These facts are, however, still too isolated to allow of our 

 coming to any definite conclusions from them. The conditions 

 are complicated, and systematic investigations must be made at 

 all seasons, for many years, if any complete knowledge of the 

 system of currents is to be gained. 



The observations that have already been carried out but shew 

 the hydrographical variations in the Northern Ocean to be so 

 great, that they may be presumed to have an important influence 

 on the changes which both the migration of the fishes, and the 

 meteorological conditions prove to exist from one year to another. 

 The connection between the hydrographical conditions and the 

 meteorological, has already been indicated by 0. PETTERSSON [96], 

 and still further reported on by MEINHARDUS [98]. 



By means of the International co-operation now being carried 

 on, the question will undoubtedly be solved, though craving much 

 labour, and it can hardly be expected that any great results will 

 be arrived at until the investigators have a sea-going steamer at 

 their disposal throughout the entire year. Up to the present they 

 have been dependent on the goodwill of private individuals, and 

 observations in the open sea have only been carried out, when 

 opportunity offered, during those seasons of the year in which the 

 sealing vessels sail to the Arctic Ocean. 



