' 30 F. L. Ekman, 



current, which prefers to run deep, is rendered very diflficult by the 

 narrow passages between the Danish Isles, and because various circum- 

 stances sometimes faciUtate and sometimes render difficult the passage of 

 the mider-current through these apertures, the supply of that current's 

 water is necessarily very irregular. 



The southern part of the Baltic is comparatively shallow, seldom 

 below 56" N. Lat. exceeding 50 fathoms (89 mètres); between the 

 southern extremity of Sweden and the German coast the greatest depth 

 is only about half that amount. Farther north to the East and North of 

 Gotland we find depths of above 100 or even 200 fathoms (178 and 356 

 met.). From some experiments, which I made in the years 1870 and 

 1871 on the saltness of different depths in the Baltic ^)^ it appeared among 

 other things, that tlie saltness in samples taken at the bottom at depths 

 of 20 and 26 fathoms (36 and 46 mètres) in the shallow line between 

 Skåne and Rügen, that is to say at the entrance of the Baltic itself, was 

 only 0.73 to 0.91 7oi whereas 32 Engl, sea-miles to the East of Born- 

 holm there was water of 47 fathoms (84 met.) depth with 1.44 "/g, and 

 at 120 fathoms (214 met.) depth to the East of Gotland with 1.12 "/^ 

 salt, and at 160 fathoms depth (285 met.) 48 Engl, sea-miles N. of Got- 

 land with 1.00 7o ^^^^- These facts place it beyond doubt,- that the un- 

 der-current in the Baltic is not continuous, but passes with greater or 

 less strength and with longer or shorter interruptions over its bottom, 

 filling its hollows. 



Although the Baltic, the Botten-sea and the Gulf of Bothnia are 

 but slightly separated from eachother, yet their waters at the surface 

 differ largely in saltness, a clear proof that the superficial current, caused 

 by the river-water, sensibly affects even these large surfaces, although 

 it may be scarcely visible to ordinary observation. Samples, collected 

 from the surface of the Gulf of Bothnia, display a saltness of from 0.15 to 

 0.35 7o5 those from Bottenhaf from 0.48 to 0.51 7o- The surface-water 

 in the Baltic, according to the specimens I examined, contained from 

 0.72 to 0.79 "/o salt, the higher number belonging to the southern part; 

 clown to a depth of 20 fathoms (36 met.) the water showed scarcely 

 any change of saltness. In the Adcinity of the Danish islands the saltness 

 of the surface-current is, as many have observed, rapidly increased, be- 

 cause it here comes more nearly in contact with the under-current, 



•) The samples were collected by two younger scientific gentlemen Docent 

 Nauckhoff and Docent Öberg, who accompanied a Swedish deep-sounding expedition. 



