186 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY. 



Suez to the Straits of Babelmandeb, which were afterwards ex- 

 amined by Dr. Giraud, who reported the following results :* 



No. 1. Sea of Suez 



2. Gulf of Suez 



3. Ked Sea 



4. Ditto 



5. Ditto 



6. Ditto 



7. Ditto 



These observations agree with the theoretical deductions just 

 announced, and show that the surface waters at the head are 

 heavier and Salter than the surface waters at the mouth of the 

 Eed Sea. 



382. Evaporation from. — In the same paper, the temperature of 

 the air between Suez and Aden often rises, it is said, to 90'', 

 " and probably averages little less than 75° day and night all 

 the year round. The surface of this sea varies in heat from 65° 

 to 85°, and the dijfference between the wet and dry bulb ther- 

 mometers often amounts to 25° — in the kamsin, or desert winds 

 to from 30° to 40° ; the average evaporation at Aden is about 

 eight feet for the year." " Now assuming," says Dr. Buist, 

 " the evaporation of the Eed Sea to be no greater than that ot 

 Aden, a sheet of water eight feet thick, equal in area to the 

 whole expanse of that sea, will be carried off annually in vapour ; 

 or, assuming the Eed Sea to be eight hundred feet in depth at 

 an average — and this, most assuredly, is more than double the 

 fact — the whole of it would be dried up, were no water to enter 

 from the ocean, in one hundred years. The waters of the Eed 

 Sea, throughout, contain some four per cent, of salt by weight — 

 or, as salt is a half heavier than water, some 2.7 per cent, in 

 bulk — or, in round numbers, say three per cent. In the course 

 of three thousand years, on the assumptions just made, the Eed 

 Sea ought to have been one mass of solid salt, if there were no 

 current running out." Now we know the Eed Sea is more than 

 three thousand years old, and that it is not filled with salt ; and 

 the reason is, that as fast as the upper currents bring the salt in 

 at the top, the under currents carry it out at the bottom. 



383. The Mediterranean Currents. — With regard to an 

 * Transact, of the Bombay Geograph. Sec. vol. ix., May, 1849, to August, 1850. 



