and it is therefore fortunate that
artificial sea-water will answer every purpose.

The composition of natural sea-water is, in a thousand parts,
approximately, as follows: Water, 964 parts; Common Salt, 27; Chloride
of Magnesium, 3.6; Chloride of Potassium, 0.7; Sulphate of Magnesia,
(Epsom Salts,) 2; Sulphate of Lime, 1.4; Bromide of Magnesium, Carbonate
of Lime, etc., .02 to .03 parts. Now the Bromide of Magnesium, and
Sulphate and Carbonate of Lime, occur in such small quantities, that
they can be safely omitted in making artificial seawater; and besides,
river and spring water always contain a considerable proportion of lime.
Therefore, according to Mr. Gosse, we may use the following formula: In
every hundred parts of the solid ingredients, Common Salt, 81 parts;
Epsom Salts, 7 parts; Chloride of Magnesium, 10 parts; Chloride of
Potassium, 2 parts; and of Water about 2900 parts, although this must be
accurately determined by the specific gravity. The mixture had better
be allowed to stand several days before filling the tank; for thus the
impurities of the chemicals will settle, and the clear liquor can be
decanted off. The specific gravity should then be tested with the
hydrometer, and may safely range from 1026 to 1028,--fresh water being
1000. If a quart or two of real sea-water can be obtained, it is a very
useful addition to the mixture. It may now be introduced into the tank
through a filter. But no living creatures must be introduced until the
artificial water has been softened and prepared by the growth of the
marine plants in it for several weeks. Thus, too, it will be oxygenated,
and ready for the oxygen-using tenants.

It is a singular fact, that water which has been thus prepared, with
only four ingredients, will, after being a month or more in the
aquarium, acquire the other constituents which are normally present in
minute quantities in the natural sea-water. It must derive them from the
action of the plants or animals, or both. Bromine may come from sponges,
or sea-wrack, perhaps. Thus artificial water eventually rights itself.

The tank, having been prepared and seasoned with the same precaution
used for the river aquarium, and having a clear bottom and a supply of
good water, is now ready for planting. Many beautifully colored and
delicately fringed Algae and Sea-Wracks will be found on the rocks at
low tide, and will sadly tempt the enthusiast to consign their delicate
hues to the aquarium. Al