Royal Society. 397 



0-000271 for 1° C. For distilled water Halstrb'm had found 0-000219. 

 Another set of more direct experiments, made at Bombay, gave for 

 the expansion of sea-water 0-000337. The difference between this 

 value and the preceding the authors refer to a change of volume of 

 the voluminometer itself, and they prefer the latter, which accord- 

 ingly they use in their reductions. 



The authors then give tables of the results of their observations, 

 which are followed by some general remarks. 



Atlantic. — The temperature of the Atlantic was found to be 



From lat. 46° to 41° N l7°-5 to 18°-5 C 



From lat. 39° to 37° 20° to 21° C. 



Mean specific gravity reduced to 17°-5 C.= 1-0277. 



The temperature and specific gravity showed very little variation 

 in the open sea, so long as no currents were met with, but in the 

 vicinity of land, disturbances of various kinds were noticed. In 

 harbours and in small bays the temperature of the water was found 

 to diminish sensibly at a depth of from 15 to 20 metres, but in the 

 open sea the temperature at the very surface was generally found 

 somewhat lower than at a depth of 30 metres, which no doubt was 

 due to evaporation. 



Straits of Gibraltar.— A current with a mean velocity of from 

 three to six miles an hour usually flows through the Straits from the 

 Atlantic into the Mediterranean. A counter current is supposed to 

 exist underneath, but the great depth of the Straits prevented the 

 authors from reaching any such current with their dipping- appa- 

 ratus, rr e rr 



East of the Straits the water of the Atlantic was met with in 

 several places, in close proximity with water of the Mediterranean, 

 from which it was distinguished by its temperature and colour. The" 

 stream from the Atlantic on passing the Straits seems to divide itself 

 into several branches. 



In connexion with the variability of the currents in the Straits, it 

 is worthy of remark that the unreduced specific gravity of the water 

 of the Mediterranean and of the Atlantic is nearly the same. 

 Mediterranean : — 

 From the Straits of Gibraltar to Malta — 



Temperature of the water 21°-7 to 22° C. 



Specific gravity reduced to 17°"5 C. . 1-0287. 

 From Malta to Alexandria— 



Temperature 23° to 24° C. 



Reduced specific gravity T0298. 



Red Sea.— The maximum of specific gravity found during the 

 voyage was in the northern end of the Gulf of Suez, 1-0393 (re- 

 duced). 



From lat. 27° to 23° N., temperature 24° to 28° C. : reduced sp. gr. 1-0315. 

 From lat. 22° to 11° temperature 30° to 31°-5 C. : reduced sp. gr. 1-0306. 

 Straits of Bab-el.Mandeb.— The water of the Gulf of Aden being 



