OF SEA-WATER IN THE DIFFERENT PARTS OF THE OCEAN. 
239 
origin. Observation, however, shows the reverse ; near the shores the water is either 
uniform throughout its whole depth, or the quantity of salt increases with the depth. 
The next question is whether we can find a similar distribution in the other parts of the 
ocean. As to the southern portion of the Atlantic, there occurs such a confused distri- 
bution of the quantity of salt in the different depths at the same place, that we are not 
able as yet to draw any conclusions from it, but must wait for more copious observations. 
, As to the other parts of the ocean, I have only very few observations from the sea 
between Africa and the Aleutic Islands; but these few observations do not show any 
regularity, or at all events seem more to incline to an increase of the quantity of salt 
with the increasing depth. The geographical distribution between land and sea is, how- 
ever, quite different in this large part of the ocean. While a strong polar current from 
Baffin’s Bay pours its cold and less saline waters into the North Atlantic Sea, the large 
mass of Asia prevents any north polar current from reaching the south Asiatic sea, into 
which the numerous great rivers of Asia send vast quantities of warm fresh water. 
As to the south polar currents, we know very little about their influence upon the 
salinity of the southern ocean; but in Sir James Ross’s ‘Voyage’ (vol. ii. p. 133) there 
is an observation upon the different specific gravity in different depths, which indicates a 
state of things similar to that in the North Atlantic Ocean. His observations are these : 
— “At 39° 16' S. lat., 177° 2' W. long., the specific gravity of the surface-water 1-0274, 
at 150 fathoms 1-0272, and at 450 fathoms 1-0268, all tried at the temperature of 60° F., 
and showing that the water beneath was specifically lighter than that of the surface when 
brought to the same temperature ; our almost daily experiments confirmed these results ” *. 
The ’principal currents of the Atlantic , the Equatorial current , the Gulf -stream , 
and the East Greenland current. 
These three currents are in fact only the same ; they begin, as is well known, in the 
Bay of Benin, under the Equator, and the main current runs straight to the west over 
the Atlantic to Cape Roque, on the east coast of South America. I certainly shall not 
try to lessen the weight of the arguments which assign the cause of this equatorial 
current to the rotatory motion of the earth, but I will only give some remarks as to 
other influences that act to the same effect. 
If we compare the quantity of salt which is found in sea-water in the region between 
* To compare these observations of specific gravity with the quantity of salt in different depths, which I 
have mentioned in the former part of this paper, I shall here refer to some experiments which I have made to 
obtain a ratio by which I could compute the quantity of salts in the sea-water from the specific gravity, and 
vice versa. I have compared, in thirteen specimens of sea-water, the specific gravity with the quantity of 
chlorine which the water contained, between 13°-75 C. (56°-75 F.) and 18°-8 C. (65°-8 F.). It was found that 
a unit in the fourth decimal place of the specific gravity of sea-water, measured by the hydrometer, is equal to 
l.ooY.ooo chlorine, the minimum being 66, the maximum 76. To find what quantity of salt corresponds to 
the specific gravity of the surface-water, as determined by Sir James Ross to he 1-0274, we must multiply 274 
by 71, which gives 19-454 chlorine in the sea-water, and that number being multiplied by the general coefft-' 
cient 1-812, gives 35-251 per 1000 salt for the water from the surface. According to the same computation the 
sea-water from 150 fathoms contained 34-993 per 1000 salt, and that from 450 fathoms 34-478 per 1000 salt. 
