162 Dr Horner on the Specie Gramty (^Sea-Water, <%"€, 
able naturalist of the expedition, and arranged according ta 
the degrees of latitude. This table evidently shows the fact, 
which is also proved by the experiments on Krusenstern’s voy- 
age, that the sea on the surface, between the tropics, is spe- 
cifically heavier, and that it contains more salt, than in higher lati- 
tudes. If we take together the statements from 25th degree 
south, as far as 25th degree north latitude ; and, in the same 
manner, from 50° to 65° degree of north latitude, the mean of 
the first is 1.0288, that of the latter 1.0245, which gives the 
difference of 0.0043 or But this by no means proves 
an absolute inequality in the saltness of the water in gene- 
ral. To give a decided opinion on it, the sfea-water must 
be fetched u]) from considerable depths, and weighed. Pro- 
bably the greater saltness arises from the rapid decrease of 
the fresh water, in consequence of evaporation. From the 
well known slowness of the transition of chemical elements 
in undisturbed compounds, this decrease is but slowly re- 
paired ; and as the upper layers are also the warmer, they 
may, notwithstanding their greater specific density, in conse- 
quence of their extent, be maintained by the warm swimming 
above the lower cooler layers, by which a principal agent of 
commixture, the difference of weight, is rendered of no effect. 
This slowness of change, and the condensation of the saline so- 
lution at the surface, which results from it, has the advantage, 
that the acceleration of the evaporation sets bounds to itself, 
because, with the increasing condensation, the attraction of the 
salt to the parts of the water is greater, and, consequently, the 
diminution of the latter less. Without this arrangement, the 
tropical seas would perhaps be covered like the frozen seas of 
the north, with constant fogs. Subsequent experiments will 
show how far our explanation of this inequality is correct ; of 
which we have now more hopes, as convenient accurate appara- 
tus have been discovered to fetch up water from any depth, at 
pleasure, and immixed. 
The considerable number of observations (there are one hun- 
dred and sixteen of them) on the temperature of the sea below 
Discovery under Baron Krusenstern. See this Journal, Vol. II. p. 356. Vol. IIL 
p. 247., Vol. IV, p. 185, — 268, VoL V. p. 206, 220, ; and Kotzebvie’s- Voya^Cy 
Vol. III. p. 425.— Ed. 
