OF SEA-WATER IN THE DIFFERENT PARTS OF THE OCEAN. 
227 
If we take the mean numbers for the five regions of the Atlantic between the south- 
ernmost point of Greenland and that of South America, we find the mean quantity of 
salt for the whole Atlantic 35*833, while the sea between Africa and the East Indies 
has only 33-850, the sea between the East Indies and the Aleutic Islands 33*569, and 
the South Sea, between the Aleutic Islands and the Society Islands, 35-219 per 1000 salt. 
The Atlantic is thus that part of the ocean which contains the greatest proportion of 
salt, which result is rather surprising if we consider the vast quantity of fresh water 
which the rivers of Africa, America, and Europe pour into it : of Africa four-fifths are 
drained into the Atlantic either directly or through the Mediterranean ; it is most pro- 
bably nine-tenths of America which is drained into the Atlantic, since the Cordilleras 
run close to the western shore of the continent ; and of Europe, also, about nine-tenths 
of the surface sends its superfluous water to the Atlantic. This greater quantity of 
fresh water from the land, and the greater quantity of salts in the corresponding sea, 
seem to contradict each other, but can be explained by a higher temperature, and, as the 
result of this higher temperature, a greater evaporation. 
Some of the large bays of the ocean have in the tropical or subtropical zone a greater 
mean than the Atlantic: such are the Mediterranean, with 37-936 per 1000 salt (mean 
of eleven observations); the Caribbean Sea, with 36-104 per 1000 (one observation); 
the Eed Sea, 43-067 per 1000 (mean of two but little differing observations), which is 
the greatest salinity of the sea I know of. 
In approaching the shores the sea-water becomes less rich in salts, a fact which finds 
its explanation in the more or less great quantity of fresh water which runs into the 
sea. On such shores where only small rivers flow out, the effect produced is but very 
trifling, as, for instance, on the western shores of South America. The effect of large 
rivers in diluting the sea-water is much greater than is generally supposed ; thus the 
effect of the La Plata river, whose mouth lies in about 35° of S. latitude, was still 
observable in a sample of sea-water taken at 50° 31' S. lat., at a distance of 15° of lati- 
tude, or 900 English miles from the mouth of the river; at about the same distance, 
the water of the North -Atlantic Sea suffered a considerable depression in salinity, pro- 
bably owing to the water of the St. Lawrence. This influence is of a double kind, 
partly in diluting the sea-water, partly in mixing it up with organic substances that 
will occasion its decomposition by putrefaction. 
The polar currents contain less salt than the equatorial. I have determined the 
quantity and nature of the salts in two very well-defined polar currents, — the West- 
Greenland polar current, with 33-176 per 1000 salt, and the Antarctic polar or Pata- 
gonian current, on the west side of South America, which contains 33-966. It is highly 
interesting to observe that the East Greenland current, which according to its geogra- 
phical relations might be considered as a polar current, which in fact has been con- 
sidered in that way, has a very high mean quantity of salt, viz. 35*278 per 1000, while 
the sea to the north of Spitzbergen, according to one analysis, contains 33-623 per 1000 
salt. I think I shall afterwards, from other phenomena also, prove that the East 
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