154 PETTERSSON OCH EKMAN, SKAGERACKS OCH KATTEGATS HYDROGRAFI. 



Plate v, section 7, Fjellbacka — Fredriksvsern. 

 » 8, FredriksvEern — Strömstad. 

 F. L. Ekman's section, Koster — Fredriksvajrn from July 1877. 

 » » » » Hållö— Ö. Fvisör from July 1877. 



section 9, Hållö — Öster-Risör Feb. 1890. 

 Plate VI, section lOA, The Gullmarefjord in Feb. 1890. 



» 10 B, » » » June & July 1890. 



Plate VII, » 10 C, » » » August 1890. 



» 10 D, » » » February 1891. 



Plate VIII, G. Ekman's section, Skagen — Vinga from June 1876. 



» » » Skagen — Pater Noster from June 1876. 



F. L. Ekmans section, along tlie estuary of the river Göta Elf from Aug. 1875. 

 Section 11, our section along the estuary of Göta Elf Feb. 1890. 



In all these sections the isosalinic lines denoting a saltness of 35 Voo; 34 Voo» 33 

 Voo etc. are drawn blue and the isothermic lines or lines of equal temperature are red. 



The State of the superficial strata is represented on the three maps in plate II, IX 

 and X. 



The salinity of the surface-water in the dififerent parts of the North Sea, the Ska- 

 gerack and the Kattegat is represented by blue, green, and yellow (see the index of co- 

 lours on pl. IX). The sections 1 — 3 on plate IX represent the saltness in the deeper 

 strata of the North Sea according to the observations of the Drache-cxpedition in the sum- 

 mers of 1882 and 1884. Figs 4 and 5 are identical with our sections from Feb. 1890 

 (1 on pl. III and 9 on plate V) and fig. 6 with F. L. Ekman's section between Hållö — 

 O. Risör in July 1877 (see pl. V). Fig. 7 is a section made by G. Ekman and A. Cro- 

 nander from Fredriksvsern to the Skaw in June 1876. The coloration of the deep strata 

 in section 1 — 7 shews the same scale of saltness as that of the maps. The maps in plate 

 IX and plate X represent the relation of the waters of the Baltic stream in summer (plate 

 IX) and in Avinter, i. e. February and March (plate X) to the surrounding saltwater of 

 the Atlantic and the North Sea. 



Plate II is a map of the Skagerack and Kattegat, on which the saltness of the sur- 

 face water is represented by the same colours as in plates IX and X. It must be ex- 

 pressly noted that this map represents the state of the surface from Feb. 13 — 19, 1890. 



The reader will easily realise the hydrographic conditions which prevailed during 

 the time of the expedition, if he compare the sections on plates III — VIII with the position 

 of the stations as given on the map in pl. I and the coloured areas on the maps and 

 sections in pl. II, IX and X. 



It Avill be seen from section 1 on plate III, which follows a line crossing the en- 

 trance to the Skagerack from the Skaw to Christiansand that the water strata of dififerent 

 saltness, which are represented by six different coloui"s in maps IX and II, are superposed 

 upon each other in the basin of the Skagerack. A closer inspection of section 1 shows 

 that the limits of temperature represented by the isothermic (red) lines almost coincide 

 with the limits of saltness (isosalinic or blue lines). 



