and becoming concentrated, it is only necessary
to prevent that concentration by pouring
in again, as pure water, whatever is poured
out as watery vapour. When the tank, pan,
or bottle, is first filled with water from the
sea, and stocked with animals, let the sea-
level on the side of the vessel be marked and
afterwards maintained by pouring in, when
necessary, distilled water, or river water—
which will generally do as well. Of course,
the use of a little hygrometer, to keep the
density always at about tiie density of the
Atlantic—one thousand and twenty-seven—
would ensure greater accuracy and a more
complete success.

So constant is the pleasure furnished even
by a small amateur aquarium, that we think
we may as well give all the information
necessary to enable any of our readers to
establish one. When we have done that, we
will touch briefly on one or two of the
charming sights that may be seen by the
possessor of a saucerful of stars, sea-worms,
periwinkles, prawns, and little fishes.

The first consideration, when one sets
practically to work, is, shall the aquarium be
small or large, and how much shall be spent
upon it? An old quinine bottle—a wide-
mouthed glass bottle, able to contain a few
ounces of water—a thing like a small glass
blacking-bottle—may be had for a few pence
of almost any chemist, and will hold several
sprays of growing sea-weed and two or three
animals most worthy to be diligently watched;
or a common tumbler, a white finger glass, a
shallow pan of any kind, may be put to the like
excellent use. Over whatever vessel is employed
a plate of glass should be laid, to retard
evaporation and to keep out dust and dirt; this
plate being occasionally lifted to renew the
air below it, and not fitting on the vessel with
a very suffocating closeness.

The orthodox aquarium is a tank or cistern,
with glass sides and a slate bottom, perhaps
also with two or three sides of slate, and
made of any convenient size or shape, to fit,
perhaps, into a window-seat, or into some
nook in a hall or greenhouse. It should be
placed where the sun's light penetrates it
freely; but, by help of a muslin shade, or some
other defence, it should be protected, if necessary,
from the sun's excessive heat. Light is
the great vivifying influence; were too much
heat, however, to strike with it upon a little tank
of sea water, the temperature of the mimicocean
would be raised unduly, and most of the
living creatures in it would be killed. The
sides of the aquarium should be set together
in a stout framework of zinc, and joined with
Scott's cement. However joined, care should
be taken that it is well soaked and seasoned
before any animals are introduced into it; for
it is marvellous how small a chemical infusion
in the water is enough to kill an entire stock
of animals. Artificial rock work has to be
made in the tank, not only for ornament, but
to provide dens and holes for those creatures
who are constituted with a taste for lying
snug. This rockwork may be fixed upon
a layer of Roman or Portland cement, which
hardens under water; but all free lime must
be soaked out, after the building of the
premises is finished. The rockwork must lie
under water, and the water must be
frequently renewed, for at least a month before
the sea water is poured in, and the sea plants
and animals are introduced.

The absolute necessity of having the sea-
water free from alloy has also to be borne in
mind when it is first collected. The captain
of a Thames steamer plying into open sea,
will for a trifle fill the vessel entrusted to
him for that purpose by any Londoner; but
however the sea-water is got, it must be
dipped up into a vessel or vessels that
communicate no taint. Perfectly clean stone jars
should be used, or a cask perfectly new; oak
casks give out tannin, and ought to be filled
with fresh water every day, for weeks before
such use is made of them; but casks of fir-
wood are less likely to do mischief; and
clean stone jars are safest of all. The bungs
or corks employed ought to be new. "I
knew," says Mr. Gosse, whose book on "The
Aquarium" is our authority for nearly all
that is said in this paper; "I knew an
instance in which a consignment of animals
was lost, from no traceable cause, except that
the water-cask, which was quite new, had
been stopped with a bung, which had been
previously used in a jar of some chemical
solution; yet the bung had been, as was
supposed, thoroughly soaked and cleansed."

The receptacle duly prepared, rockwork
and mimic sands laid down, and a small
ocean of pure sea-water poured in, the sea is
ready to be stocked with plants and
animals. Sea-weeds that have a habit of
dying off into slime and filth, or that do not
endure captivity, are to be avoided. The red
and green weeds are found to be those best
suited for the purposes of an aquarium. They
must be gathered carefully with a chisel and
hammer while growing under water, and
carried away with the fragments of rock to
which they are found attached. All pieces of
rock should be carefully cleaned before they
are introduced with attached sea-weeds, into
the aquarium; otherwise, there are things
on their surface that will die and spoil the
water. Living sea-weeds may be sent from
the sea-side carefully packed in tin boxes
between wet refuse weed. Actiniae, molluscs,
some Crustacea, and other animals, may be
sent in the same way; others in water, with
of course due and tolerably obvious precautions.
If sent far inland, they should always
go by a fast train, and be met at the last
station, or directed to be forwarded to
their destination instantly by special
messenger. They cannot be too soon let loose in
a fresh pan of sea-water at their future home.
However and wherever the change from the
great sea to the little sea may be made, some