260 A Brief History of a Marine TanJc. 



kingdom, but they may be made representative of rockpools 

 and recesses. We may treat them as spoonfuls of water, and 

 achieve such success as spoonfuls admit of; but we must not 

 suppose we have the sea at our command, and a choice for 

 our amusement of all its vegetable and animal denizens. Yet, 

 strange to say, all the early experiments proceeded on the 

 assumption that a tank is a miniature ocean. Now the ocean 

 somewhere is deep, and so, accordingly, the tanks were at first 

 made deep, and that was the greatest of all the blunders that 

 then abounded in the incipient realm of aquarian practice. 

 After hecatombs of victims had been offered up, it was found 

 that shallow tanks answered better than deep ones. I had the 

 good fortune to call attention to the importance of shallow 

 tanks and subdued daylight in the Booh of the Aquarium, 

 in time to contribute to that consolidation of aquarian princi- 

 ples which has resulted in the establishment of extensive tidal 

 aquaria at the gardens of the Zoological Society of London, 

 the Societe d' Acclimatization at Paris, and the still more 

 important and successful Aquaria at Berlin. It cannot be 

 profitless to note the several points that have been succes- 

 sively demonstrated and established, because many persons 

 are commencing the study of marine zoology, and need a 

 little help from those who have had experience, and because, 

 also, many who have had aquaria in their keeping for a series 

 of years have not yet fully availed themselves of all the know- 

 ledge that has been accumulated on the subject. 



Deep tanks are deep delusions. If it were possible to be 

 content with a mere film of water over the animals they would, 

 as a rule, prosper better than in depth enough to be com- 

 pletely submerged. The grand object is to present to the 

 influence of the atmosphere the greatest possible extent 

 of surface, and in shallow tanks this is of course ac- 

 complished. The slope-back tank is a heavy and rather 

 cumbrous vehicle, and foe that reason it surpasses every 

 other form where it is not possible to establish a tidal 

 arrangement. The great mass of slate is not quickly influ- 

 enced by changes of temperature, and the slope affords a great 

 extent of rocky bottom for a picturesque disposition of the 

 interior, and for the full growth of oxygen-making vegetation. 

 This form also allows of the transmission of light in a subdued 

 form, and an excess of light is impossible. Lastly, if the 

 creatures confined in the vessel are of a roving habit, this 

 propensity is encouraged, and wherever they roam they still 

 remain visible. 



Setting aside the notion of forming a complete submarine 

 garden and zoological collection, let us consider the case some- 

 what in detail. The tank contains but a small bulk of water, 



