the Ocean at Different Depths. 13 
observations. Leaving out this latter observation, we may conclude 
that from the equator to 45° N. lat. the water of the sea to the depth 
of one thousand fathoms possesses the same degree of saltness. © 
M. Lenz gives also two tables exhibiting the results of 258 ob- 
servations made on the saltness of the sea at the surface, 105 of them . 
made in the Atlantic Ocean, between 56° 41’ S., and 50° 25’ N. lat., 
and 153 in the South Sea and Indian Ocean, between 57° 27’ S. 
56° 22’ N. Lat. From these tables he deduces the following re- 
sults :— 
4. The Atlantic Ocean is salter than the South Sea; and the In- 
dian Ocean, being the transition from the one to the other, is salter 
towards the Atlantic on the west than towards the South Sea on 
the east. 
2. Ineach of these great oceans there exists a maximum of saltness 
towards the north, and another towards the south,—the first is far- 
ther from the equator than the. second. The minimum between 
these two points is a few degrees south of the equator m the Atlan- 
tic Ocean, and probably also in the South Sea, though Mr. Lenz’s ob- 
servations do not extend to latitudes sufficiently low in the South Sea. 
3. In the Atlantic Ocean the western portion is more salt than 
the eastern,—in the South Sea the saltness does not appear to differ 
with the longitude. 
4, The greatest specific gravity is found in the Atlantic at the 
maximum point above alluded to, at 40° W. Long—t.02856. : 
In the South Sea at 11° 9’ eee: 1.028084. 
This last is the only one in the South Sea giving a specific gravity 
reaching 1.028. 
_ 5. In going north from the northern maximum, and south from 
the southern maximum, the specific gravity diminishes constantly as 
" “Whence then, says M. Lenz, come these maxima towards the 
north and south, why is the maximum not rather at the equator ? To 
answer this question, we must inquire what chiefly determines the 
saliness of the surface. Evaporation exercises the greatest influence, 
and by this evaporation the occurrence of these maxima may be 
explained. In fact, evaporation is influenced both by the heat of the 
sun, and by the more or Jess rapid motion of the currents of air. The 
solar heat is greatest on the equator, but there, on the other hand, 
the motion of the air is least. It is remarkable that in the Atjantic 
Ocean the minimum coincides precisely with the locality of almost con- 
