58 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



charged into its basin by the Danube, the Dnieper, the Don, 

 and other rivers. This inflow, being greatly in excess of the 

 evaporation from the surface of the Black Sea, keeps down 

 the salinity of its water to an average of about two fifths 

 that of ordinary sea-water. 



It is, therefore, evident that, as the outer current is con- 

 tinually carrying away a portion of its salt, the basin would 

 in time become entirely filled with fresh water but for some 

 return of salt water from the iEgean, and he maintained that 

 this is supplied most probably by an under-current flowing 

 inward. The truth of this prediction on the part of Dr. Car- 

 penter was contested by Captain Spratt, on the ground of 

 experiments made by him during the survey of these straits, 

 this officer maintaining that, on the contrary, the water of the 

 Dardanelles below twenty fathoms is motionless, and that the 

 salt water finds its way back into the Euxine as a surface 

 current when the rivers are low and the wind sets alone: the 

 straits from the -^Egean. 



Quite recently 9 the controversy has been decisively settled 

 by experiments conducted by the surveying staff of the Shear- 

 water with a large current drag. This was suspended in the 

 deeper stratum of the Dardanelles from a boat, which was 

 carried along by it in opposition to the surface current, which 

 is said to have been even stronger than the steam-power of 

 the launch of the Shearwater. This under-current was found 

 to be flowing at twenty fathoms from the surface, precisely 

 the depth assigned to it by Dr. Carpenter, as deduced from 

 the discussion of Captain Spratt's own experiments. \5 A, 

 October 26, 1872, 534. 



CARBONIC ACID IN SEA-WATER. 



Oscar Jacobsen, of Kiel, has made a communication to 

 Nature in reference to the carbonic acid in sea-water, the de- 

 termination of the amount of this gas being considered a 

 matter of much importance in deep-sea researches. He states 

 that the complete expulsion of oxygen and nitrogen from sea- 

 water presents no difficulty, the comparative proportion of 

 the two gases not being 'sensibly different in the first and 

 last portions of the gas expelled. Carbonic acid is only par- 

 tially driven off by boiling the sea-water for hours in a va- 

 cuum, and the proportion of acid found in the expelled gas 



