236 Rustic Adornments. 
prises, it is less easily accomplished, and calls for a larger exercise of judgment, 
and a more complete knowledge of first principles. 
As it is not intended to treat any subject scientifically in this volume, the 
reader is desired to dispense with discourses on the reciprocity of influences, 
chemical, mechanical, and vital, concerned in the maintenance of “ the 
balance ” which it is the first object of the manager of an aquarium to secure. 
Neither shall we attempt to trace the history of the experiments by which this 
valuable auxiliary to scientific study has been established on so firm a basis 
that the aquarium has become a public institution • and no one interested in 
the subject would willingly forego the pleasure of visiting Paris, Hamburg, 
and Berlin, expressly to see what has been accomplished in this respect in 
those cities. A good public aquarium is a thing as yet unknown in the 
British Islands, but we may, at all events, learn how it should be constructed 
and managed by the examples afforded in continental cities. The aquarium 
is to be regarded here as a recreation, and though we must be practical, we 
need not be dry, and we do not intend to indulge in technicalities or scientific 
disquisition beyond the most obvious necessity of the practical treatment 
required. 
An aquarium, whether filled with fresh or salt water, and no matter whether 
large or small, is a prison; and as birds in cages require special care to 
compensate them for confinement, so gold-fishes and sea-anemones must be 
looked after, with love of course, for there can be no success without that, 
but also with skill, for the merely putting so many creatures into a tank is 
not to establish an aquarium. A few fundamental principles must be borne 
in mind at every stage of the enterprise. These may be explained in few 
words. In the first place, then, all the inhabitants of the waters, the lively 
fishes, the sleepy actiniae, the awkward crabs, all without exception, breathe 
at7nospheric air. It is true they do not gulp in dry air as we do, but they 
sift out, as it were, from the water, the air contained in it, and if it so 
happens that it contains none they die, and there is an end of them. It is 
usually said in the books that it is absolutely necessary to keep healthy 
vegetation in an aquarium for the purpose of generating oxygen to supply 
the animals with the means of breathing. It will be shown further on that 
this is not absolutely necessary, and in some cases not even desirable. Never¬ 
theless, oxygen the animals must have, and to secure its constant presence in 
the tank must be the first care of the keeper of an aquarium. 
Remembering that the tank is a prison, we must remember also that prisons 
