o, must be of slate, as cement
will not stick to glass. The frame should be iron, zinc, or well-turned
wood; the joints closed with white-lead putty; the front and back of
glass. There is one objection to having the side which faces the light
of transparent glass, and that is that it transmits too much glare of
sunlight for the health of the animals. In Nature's aquarium the light
enters only from above; and the fish and delicate creatures have always,
even then, the shady fronds of aquatic plants or the shelter of the
rocks,--as well as the power of seeking greater depths of water, where
the light is less,--to protect themselves from too intense a sunshine.
It is, therefore, sometimes advisable to have the window side of the
aquarium made of glass stained of a green color. It is desirable that
all aquarial tanks should have a movable glass cover to protect them
from dust, impure gases, and smoke.

When we speak of an aquarium, we mean a vessel holding from eight to
thirty gallons of water. Mr. Gosse describes his larger tank as being
two feet long by eighteen inches wide and eighteen inches deep, and
holding some twenty gallons. Smaller and very pretty tanks may be
made fifteen inches long by twelve inches wide and twelve deep. Great
varieties in form and elegance may be adapted to various situations.

There are two kinds of aquaria, the fresh- and the salt-water: the one
fitted for the plants and animals of ponds and rivers; the other for the
less known tenants of the sea. They are best described as the River and
the Marine Aquarium, and they differ somewhat from each other. We shall
speak first of the fresh-water aquarium.

The tank being prepared, and well-seasoned, by being kept several weeks
alternately full and empty, and exposed to the sun and air, so that all
paint, oil, varnish, tannin, etc., may be wholly removed, the next thing
is to arrange the bottom and to plant it. Some rough fragments of rock,
free from iron or other metals that stain the water, may be built into
an arch with cement, or piled up in any shape to suit the fancy. The
bottom should be composed entirely of shingle or small pebbles, well
washed. Common silver sand, washed until the water can be poured through
it quite clear, is also suitable.

Mould, or soil adapted to ordinary vegetation, is not necessary to
the aquatic plants, and is, moreover, worse than useless; since it
necessitates the frequent changing of the water for some time, in