DR ALEXANDER BUCHAN ON 



Outside Strait of Babel-Mandeb, 

 In Strait of ,, ,, 



In Red Sea, .... 



Lat. N. 



12 48 

 12 30 



21 30 



)) 



26 37 



Lona'. E. 



M 



45 55 

 43 32 



38 5 



34 35 



Depth. 

 Fathoms. 



109 

 219 

 437 

 109 



109 



219 

 328 



109 



219 

 328 



Tempera- 

 ture. 



Salinity 

 at 60°. 



Specific 

 Gravity at 

 ob. Temp. 



603 



1-0262 



1-0262 



58-6 



1-0264 



1-0266 



53-1 



1-0266 



1-0273 



74-5 



1-0281 



1-0260 



71-6 



1-0301 



1-0284 



71-2 



1-0302 



1-0285 



70-9 



10301 



1-0285 



71-2 



10302 



1-0286 



70-5 



1-0303 



1-0288 



70-5 



1-0302 



1-0287 



Thus the salinity of the Red Sea at these two stations near the Strait of Bab-el-Mandeb 

 is substantially the same from 109 to 328 fathoms, and this is virtually the mean 

 annual salinity of the surface from lat. 25° to 27° N. ; and probably it is the same at all 

 depths lower than the ridge separating the Red Sea from the Arabian Sea, which is about 

 200 fathoms. 



On the other hand, the specific gravity near Suez is 1*0297, but from this point it 

 steadily diminishes, owing to the decrease of the salinity and the increase of temperature, 

 to 1'0246 in the Strait of Bab-el-Mandeb, and, still further, 1*0243 to the south-east of 

 Aden. 



But the most important consideration is the enormous difference between the salinity 

 and specific gravity in the Red Sea itself and in the Arabian Sea adjoining. Thus, while 

 at depth of 109 fathoms the salinity at the above two stations in the Red Sea is 

 1-0302 and 1-0301, it is 1-0281 in the Strait of Bab-el-Mandeb, and only 1-0262 to the 

 south-east of Aden; but, as regards the specific gravities, the figures are 1*0286 and 

 1 -0284 in the Red Sea; in the strait, 1-0260 ; and off Aden, 1-0262. It follows that the 

 mean annual salinity of the inflowing surface current is 1*0279 in the strait; but the 

 outflowing under-current at the same place at depth of 109 fathoms is 1-0281, and at a 

 depth of about 200 fathoms, being the depth of the ridge separating the Red Sea from the 

 Arabian Sea, it is in all probability 1 *0302. In brief, the mean annual temperature, 

 .salinity, and specific gravity of the inflowing surface current and outflowing current at 

 depth of about 200 fathoms are these : — 





Temperature. 



Salinity. 



Specific Gravity. 



Inflowing surface water, 

 Outflowing current over ridge, 

 Differences, ..... 



82-0 

 71-0 

 11-0 



1-0279 

 1-0302 

 0-0023 



10246 

 1-0285 

 0-0039 



