The Mediterranean Sea 221 



1-0120 to 1-0140. It will thus be seen that the water of the 

 Mediterranean proper is very much salter than either the 

 Atlantic on the west or the Black Sea on the east, and this 

 great density of the water affords a useful means of recognising 

 it when investigating the interchange of waters which takes 

 place at the two extremities of the sea. Both the temperature 

 and the specific gravity of the water are evidences of the local 

 climate. The great concentration of the water shows how dry 

 the atmosphere at the surface must be, and how insignificant 

 the contributions of fresh water. With regard to the balance 

 existing between the two factors, evaporation and precipitation, 

 it would be impossible to give figures with any claim to accuracy, 

 but a rough estimate may be formed by taking such data as 

 Fischer has given. He puts the rainfall over the whole Medi- 

 terranean drainage area at 759-4 millimetres, or almost exactly 

 30 inches. If we remember that the average rainfall of the 

 eastern slopes of Great Britain is less than 30 inches, and that 

 therefore this may be taken as the maximum yearly supply to 

 the North Sea, we may be sure that the Mediterranean does 

 not receive more than 30 inches of fresh water in the year 

 With regard to the rate of evaporation over the area of the 

 Mediterranean there is but very meagre information, but 

 wherever it has been observed it has been found to exceed the 

 rainfall, even as much as three times. Thus at Madrid it is 

 65 inches, or more than four times the rainfall, at Rome 105 

 inches, and at Cairo 92 inches. It may therefore without 

 exaggeration be assumed that the evaporation is at least twice 

 as great as the precipitation. Putting the latter at 30 inches, 

 we should have 60 inches for the yearly evaporation, and a 

 balance of 30 inches evaporation over precipitation. Were 

 tin TC no provision for making good this deficiency, the level 

 of the Mediterranean would sink until its surface was so far 

 contracted as to lose no more by evaporation than would be 

 supplied by rain and rivers, ThU condition would probably not 

 be fulfilled before all the ^gean and Adriatic and the whole of 

 the western basin west of tin- isl.md of Sardinia were laid dry, 

 no-A the Medit ' would he reduced to two 



"Dead Seas," one between Sardinia and Naples and the other 



