18 
PROFESSOR GRAHAM ON THE DIFFUSION OF LIQUIDS. 
by the diffusive process, which will bring up salts of the alkalies with more rapidity 
than salts of the earth, and chlorides, of either class, more rapidly than sulphates. 
The composition of water near the surface must therefore vary greatly, as this pro- 
cess is more or less advanced. 
(4.) I may be allowed to add another experiment which is curious for the pro- 
tracted immobility of a column of water which it exhibits, as well as for the separa- 
tion occurring, which last may be interesting also in a geological point of view. A 
plain glass cylinder with a foot, 1 1 inches in height, and of which the capacity was 
64 cubic inches, had 8 cubic inches poured into it of a saturated solution of carbonate 
of lime in carbonic acid water, containing also 200 grs. of chloride of sodium dis- 
solved. Distilled water was then carefully poured over the saline solution, so as to 
fill up the jar, a float being used and the liquid disturbed as little as possible in the 
operation. The mouth of the jar was lastly closed by a ground glass plate, and it 
was left undisturbed upon the mantelpiece of a room without a fire, from March 20 to 
September 24 of the present year, or for six months and four days. Afterwards, on 
removing the cover, the fluid was observed not to have evaporated sensibly, and it 
exhibited no visible deposit. This I was not surprised at, as no deposit appeared in 
a similar experiment with the jar uncovered, after the lapse of six weeks. The liquid 
in the former jar was now carefully drawn off by a small siphon with the extremity 
of both its limbs recurved so as to open upwards, in four equal portions, which may 
be numbered from above downwards. Equal quantities of the four strata of liquids 
gave the following proportions of chloride of sodium and carbonate of lime : — 
Chloride of sodium. 
Carbonate of lime. 
No. 1. 
21-91 
0-10 
No. 2. 
23-41 
0-22 
No. 3. 
23-55 
0-38 
No. 4. 
23-99 
0-42 
The diffusion of the chloride of sodium has therefore not yet reached complete uni- 
formity, although approaching it, the proportion of that salt obtained from the top 
and bottom strata being as 11 to 12. But the diffusion of the carbonate of lime ap- 
pears much less advanced, the proportion of that substance being as 1 to 4 at the 
top and bottom of the liquid column. The slight difference in density of the strata, 
it may be further remarked, must have been sufficient to preserve such a column of 
liquid entirely quiescent, as shown by the distribution of the carbonate of lime, during 
the considerable changes of temperature of the season. 
Chemical analysis, which gives with accuracy the proportions of acids and bases in 
a solution, furnishes no means of deciding how these acids and bases are combined, 
or what salts exist in solution. But it is possible that light may be thrown on the 
constitution of mixed salts, at least when they are of unequal diffusibility, by means 
of a diffusion experiment. With reference to sea-water, for instance, it has been a 
question in what form the magnesia exists, as chloride or as sulphate ; or how much 
