Page:The Book of the Aquarium and Water Cabinet.djvu/17

Rh kinds hitherto the least studied by naturalists, displaying to our close gaze their natural forms, and colours, and instincts, and economy, as freely and as happily as if they were still hidden from us in their native depths. In this sense, the aquarium remunerates for any trouble it may cost, in the lessons it affords of the workings of Almighty Wisdom, in those regions of life and wonder to which it introduces us.

The Philosophy of the Aquarium must be clearly understood by those who purpose to cultivate it. It is a self-supporting, self-renovating collection, in which the various influences of animal and vegetable life balance each other, and maintain without the vessel a correspondence of action which preserves the whole. A mere globe of fish is not an aquarium in the sense here indicated; because, to preserve the fish for any length of time, the water must be frequently changed; and even then the excess of light to which they are exposed, and the confinement in a small space, in which they quickly exhaust the vital properties of the water, are circumstances at variance with their nature, and sooner or later prove fatal to their lives.

In an aquarium, the water is not changed at all, or at least only at long intervals, as we shall explain hereafter; and besides the enclosure of fishes in a vessel of water, growing plants of a suitable kind, always form a feature of the collection. Formed on this plan, an aquarium is an imitation of Nature on a small scale. The tank is a lake containing aquatic plants and animals, and these maintain each other in the water in the same way as terrestrial