NATURE 



n 



THURSDAY, NOVEMBER 25, i5 



EXPLORATION OF THE NORTH SEA 

 Die Ergebnisse dcr Unfcrsuchtingsfahrten S.M.Knbt. 

 "Drache" {Kinnmandant Korvette?!- Kapitdn Holz- 

 hauer) in der Nordsee in den Sommern 1881, 1882, imd 

 1884. Veroffentlicht von clem Hydrographischen Amt 

 der Admiralitat. (Berlin : Ernst Siegfried Mittler und 

 Sohn, 1886.) 

 /^UR knowledge of the physical conditions of the 

 ^-^ North Sea has just been enriched by the publica- 

 tion of the results of the expeditions of the Prussian ship 

 D>-ache during the summer months of the years 1881, 

 1S82, and 1 884. The expeditions and the publication 

 liave been carried out under the direction and with the 

 authority of the Hydrographic Office of the German 

 Admiralty. 



Prof. Mobius, who has examined the organisms col- 

 lected by the Drache, reports that he has found nothing 

 worthy of special mention among the biological collec- 

 tions. It is otherwise with the physical and chemical 

 observations, for the whole of the volume before us is 

 devoted to these observations, their analysis and dis- 

 cussion. The publication is accompanied by synoptic 

 tables showing the positions of the observing stations 

 and the scientific results, as well as by fourteen charts 

 setting forth graphically the currents, the depths, the 

 salinity, specific gravity, and the quantity of oxygen in 

 the surface, intermediate, and bottom water, and sections 

 illustrating the distribution of temperature. 



The temperature and salinity are first examined. The 

 observations confirm the view that the salt heavy water 

 of the Atlantic enters the North Sea by the north of 

 Scotland, and, on being cooled, sinks to the bottom, and 

 fills all the deeper parts of the basin, including the 

 Norwegian Gut. The observations of the Norwegians 

 and those on board the Triton showed that, in like man- 

 ner, the deep water of the Norwegian Sea was largely 

 made up of the salt Atlantic water, which sank to the 

 bottom on reaching a colder latitude — probably mixing 

 much with deep colder Polar and fresher water. The Drache 

 traced this salt Atlantic water to the centre of the North 

 Sea. It would be a matter of very great interest to have 

 the temperature of the water taken at stated intervals 

 throughout the year in the Norwegian Gut, in a similar 

 manner to the observations now being carried on in the 

 deep lochs of the west of Scotland. The observations 

 on the currents of fresher water running to the north 

 along the coasts of Britain and Jutland — the latter eventu- 

 ally meeting and mixing with that of the Baltic — are very 

 interesting. Indeed, the extensive current and tidal ob- 

 servations are valuable additions to knowledge ; but, as 

 the author remarks, both they and the temperature ob- 

 servations are incomplete, being confined to the summer 

 months, and he indicates the regions where observations 

 are much required. Still, combined with the winter 

 observations which w'e possess at certain points, the 

 Drache' s observations greatly augment our knowledge of 

 the physical conditions of the North -Sea, and of the 

 modifying influences produced by the seasons. 



The chemical work has been intrusted to Dr. Neu- 

 VCL. XXXV.— No. 891 



meister, under the direction of Prof. Jacobsen, and the 

 geological part is by Dr. Gtimbel. The chemical work 

 includes the determination of the oxygen and nitrogen 

 in water from different depths. Dr. Neumeister found in 

 surface-water (mean of twenty-five analyses) the o.xygen 

 to be 33'95 per cent., the volume of the sum of the 

 oxygen and nitrogen equalling 100. In deep water (200 

 metres) the oxygen descended to 25^20 per cent, of the 

 volume of the two gases. 



For carbonic acid cotiibined as neutral salts, he found 

 for surface-waters 52'66 milligrammes per litre (mean 

 of sixty-seven determinations) ; the partially combined 

 acid was found to be 4378 milligrammes (mean of 

 thirty-nine determinations). 



As appendix to these researches, the results are given 

 of the determinations of the carbonic acid in the waters 

 of the Atlantic, Indian, and Pacific Oceans, collected by 

 the Gazelle in 1874-76. The carbonic acid combined as 

 neutral salts in the surface-waters reaches to 525 miUi- 

 grammes per litre (mean of thirty-one observations). At 

 183 metres of depth, the mean is 53*2. For greater 

 depths, down to 5000 metres, fourteen determinations 

 gave 50'6 to 56'8 milligrammes. Four determinations 

 gave 59 to 70 milligrammes, and one gave S27 milli- 

 grammes. No attempt is made to compare these with 

 the Challenger results. 



The author explains the presence of the large quantity 

 of carbonic acid in deep water by the fact that the 

 water dissolves the carbonate of lime, which is found 

 in great quantity on the bottom in all moderate depths. 

 The carbonic acid which effects this dissolution is pro- 

 bably furnished by the oxidation of organic substances. 

 The author refers to the fact that carbonic acid is not 

 necessary in order that carbonate of lime may be dis- 

 solved by sea-water, and has, in this respect, confirmed 

 Dittmar's observations. Different waters, however, com- 

 port themselves very differently in this respect. The 

 water of great rivers, adds the writer, at their embou- 

 chure contains less acid combined as neutral salts than 

 ocean water, and the mixture of salt and river water, along 

 coasts,less carbonic acid than the water in the great oceans ; 

 but the difference is not in proportion to the quantity of salts 

 present. It is shown by analyses of Baltic water that 

 while this water contains only about one-half of the salts 

 present in pure ocean water, it contains nearly nine-tenths 

 of the carbonic acid present in the neutral salts of pure 

 ocean water. 



Gumbel's work consists in an examination of the de- 

 posits collected from depths ranging from 18 to 317 

 metres. The forty samples, of which an excellent descrip- 

 tion is given, all belong to littoral, sub-littoral, or terri- 

 genous deposits. None of them present the essential 

 characters of truly deep-sea or pelagic sediments. The 

 author divides them into quartz sands and sandy clays, 

 the latter being of a much darker colour than the former. 

 Giimbel has followed in his descriptions the methods indi- 

 cated in the preliminary notices of the Challenger 

 deposits. Gijmbel attributes the absence of Globigerina 

 ooze from the samples to the relatively shallow depths 

 from which they were procured, and he adds that the 

 depth determines the nature of the deposit. This is quite 

 a mistake : it is, rather, distance from land that deter- 

 mines the kind of deposit. Deposits not unlike those 



