26 2 
THE MEDITERRANEAN NAT IRA LIST 
the two seas was made, the water from the Medi- 
terranean would make its way as it does at pre- 
sent into the disappearance of the ancient fauna. 
Thus the sulphuretted hydrogen is one of the pro- 
ducts formed by the decomposition of the older 
life, and as the water in the great depth is practi- 
cally stagnant, i.e . , quite motionless, it follows 
that the decay is an exceedingly slow process. 
Assuming that the water which annually flows 
through the Bosphorus into the Black Sea forms 
a one-thousandth part of the total contents of the 
sea, it will take 1000 years to completely' renew 
the whole contents of the basin. It will be thus 
easily seen to what small extent the deep waters 
participate in the scheme of circulation. The 
>Sea of Azov is merely the expanded mouth of 
the River Don, its waters being shallow, having 
no greater depth than fathoms, and being 
thoroughly mixed by each storm that visits it. 
The Sea of Azov, too, shares in the disturbing 
influences of the surface current which sweeps 
round the shores of the Crimea to the north-west 
and then follows the trend of western shores past 
the mouths of the Danube towards the Bosphorus 
The dimensions and velocity of this current are 
augmented when the melting of the snow in the 
Black Sea basin is more rapid than usual. 
We have mentioned above that a decided influx 
of Mediterranean water takes place into the Black 
Sea. Were it not for this saline water the Black 
Sea would be much fresher than it is, and were 
the connection between it and the Mediterranean 
destroyed then the sea would become fresher, as 
there is a surplus of river and rain supply over 
evaporation. Throughout the whole length of the 
Bosphorus, the Sea of Marmora; and the Helles- 
pont, two distinct currents can be traced, the 
heavier Mediterranean v tier forming the under- 
lying stratum, moving slowly into superincumbent 
and moving in the opposite direction. There ap- 
pears to be very little mixing of the two currents, 
the layer of demarcation between the two being 
easily detected by the difference in the specific 
gravities of the two aqueous masses. 
The comparatively fresh water that the Black 
Sea contributes to the waters of the Mediterra- 
nean produces but little effect, so large is the area 
of the basin into which it pours itself and so small 
relatively is the volume of water so contributed. 
The greatest depth of the Sea of Marmora is 
found along the line connecting the Hellespont 
with the Bosphorus, and ranges betv een 266 and 
355 fathoms. 
The Hellespont itself has a depth of 50 fathoms, 
while the mean depth of the Bosphorus varies 
from 30 to 40 fathoms. 
The Aegean Sea has not its specific gravity- 
reduced as might be expected below that of the 
whole Mediterranean by the influx of the Black 
Sea water. In fact its specific gravity is greater 
than that of any other section of the Mediterra- 
nean basin. 
The accompanying table bears out the truth of 
this. The figures quoted are the result of many 
observations, and are derived from samples of 
water taken from 50 miles to the w*estward of 
Gibraltar to the easternmost section of the Black 
Sea. 
Mediterranean Water ousidel 
Gibraltar / 
Mean specific gravity fori 
W estern ejection j' 
Mean specific gravity for | 
Eastern j 
Mean specific gravity for 1 
Black Sea / 
1-0260 — — 1 -0-270 
1-0280 1-0290 
1-0290 1-0300 
1-0120 1-0140 
In each case the results are derived from ana- 
lyses of surface water. 
In round numbers the area of the Mediterranean 
basin is one million square miles, and the average 
rain fail over the whole area that drains into it 
has been assessed as being equivalent to an annual 
rain -fall of 30 inches upon the sea itself. The 
amount of water removed by evaporation is greatlv 
in excess of this, probably 2i times as great. At 
Rome the evaporation is represented at some 105 
inches per annum, at Madrid it is 65 inches, and 
at Cairo 92 inches, It does not require much 
speculation to determine what would happen if 
the waters of the Mediterranean were not reple- 
nished from some external source. A shrinkage 
of the basin by a diminution of the water area 
would continue until the evaporation from the 
reduced surface would equal the amount of aque- 
ous precipieation. But before that condition 
would be reached, the shrinkage would have re- 
sulted in the drying of the bank between Africa, 
and between Africa and Gibraltar, with the result 
that two “dead seas would be formed. 
Happily, there is not much probabilityof such a 
