SPECIFIC GRAVITIES AND OCEANIC CIRCULATION. 



327 



In strong contrast with this region of low specific gravity is the specific gravity of 

 the Arabian Sea. The north-western part of this sea, together with the Red Sea and 

 Persian Gulf, is one of the driest regions of the world ; and since winds blow offshore 

 seawards, upwelling sets in there, bringing the cooler water of lower depths to the sur- 

 face, temperature is lower over the Arabian Sea than elsewhere. Consequently, from the 

 lower temperature thus brought about and the larger evaporation, owing to the prevailing 

 dry winds, the specific gravity is high. 



The Red Sea presents some interesting features. From the Monthly Charts of the 

 Red Sea # recently published by the Meteorological Council, the following annual 

 averages of surface temperature and specific gravity have been calculated : — 



Red Sea. — Mean Annual Temperature and Specific Gravity of the 

 surface of the Red Sea, 



Lat. N. 



Long 



. E. 



Temperature. 



Specific Gravity. 



At 60°. 



At obs. Temp. 



29 6 



33 



6 



72-0 



1-0313 



1-0297 



27 



34 



20 



76-1 



304 



281 



25 



35 



40 



78-4 



301 



274 



23 



37 







80-4 



299 



268 



21 



38 



10 



82-1 



295 



262 



19 



39 



30 



83-4 



291 



255 



17 



40 



40 



83-7 



288 



252 



15 



42 







83-4 



285 



249 



13 



43 



10 



81-9 



279 



246 



12 40 



45 







81-3 



276 



244 



12 45 



47 







81-6 



276 



243 



12 50 



49 







81-4 



275 



243 



Thus, the mean annual temperature of the surface is lowest, 72° '0, a little to south of 

 Suez; from which it gradually rises to the maximum 83°'7, near the centre of the sea 

 to the east of Massaua ; falls to 81 o, near the Strait of Bab-el-Mandeb ; and still 

 lower on advancing eastwards into the Arabian Sea. The approximate salinity is the 

 maximum, 1*0313, at the head of the sea near Suez, from which it steadily diminishes step 

 by step to 1 '0275 in lat. 12° 50' N. and long. 49° 0' E. Thus, the strong inflowing current 

 occasioned by the large evaporation from this sea indicates a salinity of 1*0275 as it 

 passes the Strait of Bab-el-Mandeb, which is equal to the maximum salinity of the North 

 and South Atlantic respectively. But, on advancing northwards, the salinity of the 

 surface rapidly increases till the maximum 1*0313 is reached in lat. 29° 0' N. and long. 

 33° 0' E. This is the highest mean annual salinity occurring anywhere on the globe 

 which is in communication with the open sea. 



The following temperatures and specific gravities have been observed in the Red 

 Sea by Admiral Makaroff : — 



* Meteorological Charts of the Red Sea. Published by the Authority of the Meteorological Council. London, 1895. 



