5' 



NATURE 



[November lo, 1910 



TH£ -MICHAEL SARS'' NORTH ATLANTIC 

 DEEP-SEA EXPEDITION, 1910. 



TN the month of August last year, Sir John Murray 

 approached me with the liberal offer of defraying the 

 expenses of a deep-sea expedition to the Atlantic Ocean, 

 provided the Norwegian Government were willing to lend 

 their research-vessel, Michael Sars, for the purpose. Sir 

 John Murray wished lo ascertain whether the appliances 

 and instruments used by the Michael Sars for her work in 

 the Norwegian Seas would yield new information in the 

 Atlantic. It was, besides, considered desirable to examine 

 parts of the Atlantic that had previously been only very 

 slightly explored. The Norwegian Government at once 

 signified its willingness to accept this proposal, and 1 

 accordingly employed the past winter in making prepara- 

 tions for the expedition, assisted by the captain of the 

 vessel, Mr. Thor Iversen, Prof. H. H. Gran, who agreed 

 to lead the investigation of phytoplankton, and Mr. Helland 

 Hansen, who took charge of the hydrographical researches. 

 For my own part, I decided to cooperate with Mr. E. 

 Koefoed, and to devote myself especially to zooplankton and 

 the study of the bottom-fauna. 



The expedition left Bergen at the end of March, arrived 

 at Plymouth — where it was joined by 

 Sir .John Murray — and then followed 

 the coasts of Europe and Africa down 

 to Cape Bogador, carrying out special 

 investigations in the Bay of Biscay, the 

 Bay of Cadiz, and the waters between 

 the Canary Islands and .'Africa — thirty- 

 four stations in all. It next undertook 

 ■a section into the Sargasso Sea, and 

 after touching at the Azores, proceeded 

 right across the Atlantic to St. John's, 

 Newfoundland (forty stations). From 

 there a section was taken to the south 

 coast of Ireland (twenty-two stations), 

 and, finally, we concluded our investiga- 

 tions bv examining the waters between 

 Scotland and Rockall and between 

 Scotland and the Faroes — that is to 

 say, north and south of the Wyville 

 Thomson ridge — so as to study the in- 

 fluence exerted by the Atlantic Ocean 

 upon the Norwegian Sea. The route 

 of the expedition will be seen on the 

 accompanying sketch (Fig. i). 



During this cruise we endeavoured, 

 ■so far as time permitted, to undertake 

 hydrographical and plankton investiga- 

 tions simultaneously, and we further 

 carried out a considerable number of 

 hauls with the trawl. 



The large number of observations 

 and specimens thus secured can, natur- 

 ally, not be fittingly described before 

 being systematically studied, and it is 

 accordingly only possible as yet to furnish mformation 

 regarding their nature and extent. 



Hydrographical Investigations. 



Hydrographical investigations have been carried out at 

 about 110 stations. The temperature readings were taken 

 with Richter's reversing thermometer and Nansen's thermo- 

 meter, while the water-samples were collected by means of 

 Ekman's water-bottle and the Petterson-Nansen isolated 

 ■water-bottle. At most of the stations the temperatures 

 have been recorded by two thermometers simultaneously at 

 each depth, no fewer than 519 simultaneous readings being 

 taken with the same two thermometers. The corrected 

 temperatures gave an average difference of o"oi° Centi- 

 grade. 



The difference between the two thermometers was : — 



In 168 cases o'oo° 



In 231 , o'oi° 



In 84 o-o2° 



In 36 ,, o'o3° or over. 



A fair number of simultaneous observations have been 

 made with the reversing thermometer and Nansen's thermo- 



NO. 2 141, VOL. 85] 



meter in the isolated water-bottle, with the view <> 

 observing the adiabatic effect by means of the difference i 

 pressure. Besides the temperature readings, we have tak< 

 water-samples from all depths to determine the salinity ai 

 specific gravity, and we have endeavoured to get a 

 exactitude in the determinations of salinity of o'oi-oo2 p' 

 mille, and in the density in situ an exactitude of 1-2 ; 

 the fifth place of decimals. On these lines the investigatioi 

 have been carried out along the whole route of the cxped 

 tion. We have, further, procured about 100 large water 

 samples from different stations and depths, for the purpo^ 

 of determining the quantitative occurrence of nitrogenou.-, 

 substances, particularly ammonia. 



The determinations from the deepest layers (down to 4950 

 metres) have given very uniform results, with a tempera- 

 ture of 248 C. It has been found that there is a very faint 

 increase of temperature near the bottom at great depths, 

 due, possibly, to the conduction of heat from the interior of 

 the earth or a radium effect. In the upper layers conditions 

 have varied considerably at times, especially in the neigh- 

 bourhood of the Gulf Stream area and in the western 

 portion of the North Atlantic. Here our investigations 

 furnish apparently a number of new and interesting 

 results, which, however, it is impossible to do more than 



Fig. I. 



allude to before the water-samples have been thoroughly 

 examined. 



Surface temperatures have been recorded every hour 

 during nearly the whole cruise, while every two hours a 

 water-sample has been taken from the surface with par- 

 ticulars of the different meteorological conditions (wind, 

 barometer, temperature of the air, humidity, and cloudi- 

 ness). Altogether we have about 2500 water-samples and 

 about 3000 temperature readings. 



Several series of direct-current measurements have been 

 made with Ekman's propeller current measurer. In the 

 Straits of Gibraltar the current was so strong that we 

 encountered no small difficulty in regard to anchoring. 

 However, we succeeded in the course of a day in 

 obtaining altogether seventy good measurements from 

 eight different depths between the surface and the 

 bottom. There were considerable tidal fluctuations both 

 in the west-going surface current and in the deep east- 

 going current ; simultaneously with the fluctuations in the 

 strength of the current the boundary between the two 

 streams shifted upwards and downwards, as clearly 

 appears from repeated series of temperatures and water- 

 samples. The boundary lay at a depth between 50 and 

 100 fathoms below the surface. Velocities of four knots or 



