224 
PROFESSOR FORCHHAMMER ON THE COMPOSITION 
Kaidaik, and 6-236 per 1000. The proportion between chlorine, sulphuric acid, lime, 
and magnesia, is 
100 : 44-91 : 9-34 : 21-48. 
It is quite evident that the Caspian Sea, if it ever had any connexion with the Black 
Sea, must have changed its character entirely since that time, and this change might either 
be occasioned by the different salts which the rivers brought into the lake, and which 
accumulated there by evaporation of the water, or it might be caused by the deposition 
of different salts in the basin of the Caspian Sea itself. If we now compare the abnormal 
proportions in the Caspian Sea, 
Chlorine 100, Sulphuric acid 44-91, Lime 9-34, Magnesia 21*48, 
with the normal proportions in the ocean, 
Chlorine 100, Sulphuric acid 11*89, Lime 2-96, Magnesia 11-07, 
we find that the excess of lime and magnesia will nearly neutralize the excess of sulphuric 
acid, and leave only a small quantity of sulphuric acid (3-72), which may be neutralized 
by alkalies. Thus rivers which brought sulphate of lime and of magnesia into the Cas- 
pian Sea, might in the lapse of 100 and 1000 years certainly change the composition of 
its water in the direction which it now has. Its mean coefficient is 2-434. 
Eleventh Region. The Atlantic Ocean between the Equator and 30° 8. lat. — The mean 
quantity of salts in this region, deduced from seven observations, is 36‘553, the maximum 
37-155, the minimum 35-930. The relative quantity of chlorine, sulphuric acid, lime, 
and magnesia is 100: 12-03:2-91: 10-96. The water of this region is richer in salt 
than the corresponding region in the North Atlantic Sea. Its coefficient is 1-814. 
Twelfth Region. The Atlantic Ocean between 30° S. lat. and a line from Cape Horn 
to the Cape of Good Hope. — Mean salinity 35-038, maximum 35-907, minimum 34-151; 
the maximum not far from the Cape of Good Hope, the minimum not far from the 
Falkland Islands. Its salinity is less than the corresponding region in the North 
Atlantic (Region 2), which is 35-932, even less than the third and fourth regions (the 
East Greenland current), whose salinity is 35-278. This seems partly to depend upon 
the Gulf-stream, which causes a considerable evaporation in the northern part of the 
Atlantic, partly upon the River Plata in the South Atlantic, which carries an enormous 
quantity of fresh water into the southern sea. I have analyzed four samples of sea- 
water taken under the influence of that large river. One, taken by Captain Pkevost 
in 35° 46' S. lat. and 52° 57' W. long., almost at the mouth of the Plata, contained so 
much organic matter that a great part of its sulphuric acid was decomposed, so that the 
original quantity of salt could not be ascertained, but the quantity of chlorine, which, 
as far as we know, is not affected by the fermentation of the water, was only 17-721, 
which, multiplied by 1-808, the coefficient of this region, gives a quantity of salts 
— 32-040 ; the other three samples, taken between 40° 30' and 50° 31' S. lat., and 40° 50' 
and 52° 15' W. long., are all far below the mean salinity of this region. It deserves to 
be remarked, that all the samples from the western part of this region have a less 
