6 NATURAL SCIENCE. July. 



Magazine for June, an important paper on Swedish Hydrographic 

 Research in the Baltic and the North Seas. Dr. Pettersson 

 commences by stating that "the system adopted by the Swedish 

 naturahsts at the present time, in their explorations of the sea which 

 surrounds the Scandinavian peninsula, is to despatch a number of 

 ships simultaneously from different ports across that part of the sea 

 which is to be explored, each ship being provided with a complete 

 set of hydrographic instruments, worked by assistants specially 

 trained for their task in the laboratories of Stockholm's Hogskola, the 

 Polytechnic Institute, etc. The route of each ship, and the position 

 of every sounding station, are determined beforehand, according to 

 previous experience. In every successive expedition the same 

 sounding-places are chosen, in order to ascertain the alterations 

 which have occurred in the arrangement of the water-strata. The 

 advantages of this method of research are obvious. All the observa- 

 tions being taken within a few days, the hydrographic state of a 

 certain part of the sea at all points is exhibited practically simul- 

 taneously, unaffected by changes of wind and weather." Surveys 

 of the Baltic have been undertaken in 1877, 1878, and 1879, but the 

 more systematic surveys of which this paper treats were taken 

 between 1890 and 1893. 



After treating in detail, and with illustrations, of the special 

 apparatus used, Pettersson gives specimen? of the results obtained 

 as regards temperature at various depths in the Gullmar Fjord, 

 the deepest depression of the Baltic (S.S.E. from Landsort), and the 

 deepest part of the Aaland Sea. In the Gullmar Fjord temperature 

 ranged steadily downward from 17*50 C. to 4*60 C. (60 metres), then 

 rose again gradually to 5-04 C. (120 metres, bottom). In the Lands- 

 ort series the temperature marked i3"o6 C. at the surface, 2*15 C. 

 (60 metres), rose again gradually to 4 C. at 280 metres, to sink again 

 to 3-95 C. at bottom (400 metres). In the Aaland Sea 8-05 C. was 

 registered at the surface, i-8o at 30 metres, 2-95 from 40-70 metres, 

 and then a steady fall to 1*65 at 265 metres (bottom). Full instruc- 

 tions are given for the method of obtaining analyses of gases 

 dissolved, and the determination of the total carbonic acid contained 

 in sea-water, as well as chlorine titrations, specific gravity, and 

 salinity. A description is then given of Pettersson's Plankton 

 apparatus, the results obtained with which showed that water-layers of 

 different origin and diiferent depths contained different and charac- 

 teristic forms of animal life. For instance, on 2nd August, 1893, the 

 biologists accompanying the expedition distinguished three strata of 

 water in the Gullmar Fjord, which showed marked differences with 

 regard to temperature and salinity, and marked differences in the 

 fauna. The detailed results are given in the pages, but space pre- 

 cludes our inserting them here. Dr. Aurivillius is now engaged on 

 an investigation of the animals obtained, and we await his results 

 with interest. The final paragraph of this interesting paper is 



