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218 AQUARIUM and opportunity for skilled naturalists pursuing delicate scientific investigations. The modern aquarium is essentially different from the vivaria or fish-stews of ancient times. These were con structed for every day kitchen use, for the purpose of sup plying the tables of their wealthy possessors with various kinds of fish ; some of those kept being of great value. Wonderful stories are told by ancient authors of the pains taken to procure fine breeds of fish, and the care with which they were fed and fattened for use. Fish were bor rowed and returned ; the keeping of them became a fashion, and extravagant sums of money were expended on the pur chase of rare kinds. The remains of vivaria and fish-stews are still to be found in the neighbourhood of Naples, and at other places in Italy. The dimensions of the great aquarium at Brighton are as follows: Its area is 715 feet in length by 100 feet in breadth. It contains many tanks, some of them being of SIDE FACING THE SEA Ground Plan of Brighton Aquarium. A, entrance court ; B, entrance-hall and reading-room ; C, restaurant ; D, D, western corridor ; E, E, eastern corridor ; F, F, tanks (all shaded in plan) ; F G, the large tank, No. 6; G, conservatory; H, rockwork, fernery, and cascade; I, I, space with tanks on table ; J, J, engine, stores, Ac.; K, rockwork with ponds for seal, &c. ; L, grotto ; M, heating apparatus. vast capacity ; there is one in particular (No. G) which con tains 11 0,000 gallons of water, and has a plate-glass front 130 feet long, through which the habits of very large fish may be studied. The rock-work of the tanks is entirely artificial, and admirably adapted to afford shelter to the fish and crustaceans which disport in them. The management of a large aquarium, such as that at the Crystal Palace or at Brighton, involves constant anxiety and daily trouble : the fish must of course be fed so that they may enjoy good health, and to ensure this they must live under condi tions as nearly as possible the same as they have been accustomed to in the waters from *vhich they have been taken. At one time much difficulty was experienced in keeping the inhabitants of sweet-water tanks in good health; in numerous instances the fish died in a day or two after their places of residence had been changed ; and it was not till after many different plans had been tried, that safe modes of keeping them in a healthy state were found out. Thousands of fish died in ornamental fresh- water tanks from over- attention, from a too frequent changing of the water, and from lack of a supply of those elements of growth which are essential to all animated nature. The aquariums at Brighton and the Crystal Palace exemplify two distinct systems of construction and manage ment. At the former there is no actual circulation of water from one tank to another but it can, if necessary, be renewed from the sea ; the mass of the water in the reserve cisterns is small as compared with that in the show tanks, and aeration is effected by pumping air into the tanks through tubes of large diameter. Purification of the water is also assisted by the presence of large bivalve molluscs in the tanks. At the Crystal Palace aquarium, a constant circulation is maintained from one tank to another ; the bulk of water in the reservoir is five times as much as that in the show tanks, while aeration is accomplished by carrying a main over their entire length, from which, under pressure, a small stream of water pours from a tap into each, break ing the surface of the water, and carrying down to the bottom of the tanks, and distributing over the body of their contents, myriads of minute bubbles of air, which present an enormous oxidising surface to the water, rendering it bright and sparkling. It does not answer very well, even when an aquarium is at the sea-side, to be constantly changing the water, as the new supply is so disturbed and impregnated with impuri ties as to be fatal to delicate animals, besides not bein" in a proper state for exhibition. Some of the inhabitants of an aquarium foul the water very much more than others notably the flat fish family, and provision has to be made for this by putting such other animals in the same tank as will aid in purifying the water. Various small animals have of course to be provided as food for the larger marine specimens ; others of them act as scavengers, help ing to keep the water constantly sweet and clean. The light admitted to the fish in the tanks is also a matter of careful adjustment. As the animal life and vegetable life mutually support each other, the kind of material necessary for maintaining the " compensating system " must be watch fully supplied. Mr W. R. Hughes of Birmingham recom mends the growth of sea-lettuce ( Ulva latissima) in tanks, as suitable both for oxygenating the water and for food for the fishes ; the stock plants being introduced in the autumn months, when they are loaded with spores. Now that such excellent aquariums as those at Brighton, Manchester, Southport, and Sydenham are in full working order, the construction of others will not be difficult, even when pro jected on a larger scale. Distance from the sea is of no consequence, as sea-water may be obtained by railway, and can be kept stored as already suggested. Scientific discovery, or the promotion of experiments in natural history, is usually no direct part of the plan of modern aquariums, except in so far as this may be incidental to the daily conduct of the collection. Never theless, it is not too much to expect that the aquariums already in existence, and those which are projected, may be made useful in determining many questions connected with the life and growth of our food fishes, in regard to which naturalists and economists are alike ignorant. The fish of which we know most is the salmon, and our knowledge of that "monarch of the brook" arises froin the fact of its being accessible to constant observation. It would tend to the better regulation of our fisheries, and to the augmen tation of our food supplies, if we knew as much about the herring or the haddock as we know about the salmon. Were a large marine observatory erected by the State, say at Brighton, or were the present aquarium there consider ably extended, the best results might follow. Precise in formation might be obtained as to the period of spawning of the common herring, the length of time which the ova require to come to life, and the age at which the fish be comes reproductive. The conditions under which fish grow and remain in good health, the best kinds of food on which to feed them, the best methods of protecting them from their numerous enemies, are all questions which a properly conducted aquarium would aid our naturalists to study. It is well known that very uneconomical modes of fishing are at present resorted to, and that the largest portion of our fish is captured at a time when fish ought not to be cap tured at a time, indeed, when they are most unfit for use. It is only by studying the habits of these denizens of the ocean, in some place where they can be constantly under observation, such as a great aquarium, where the condi tions of their captivity should resemble as much as possible their native habitat, that we can ever hope to fathom the mysteries of the great deep, and ultimately have at our com mand the treasures of the sea. (See Gosse, The Aquarium, 1856 ; the Guide-Books of the Crystal Palace and Brighton Aquariums; Hughes, On the Principles and Management

of the Marine Aquarium, 1874.) (j. G. B.)