The Birmingham Aquarium.
By W. P. Marshall, esq., M.I.C.E.
The first step towards the attainment of this desirable object (now about to be realised) was the appointment of a Committee of the Birmingham Natural History and Microscopical Society four years ago, to obtain information on the subject, with the view of promoting an efficient Marine Aquarium in Birmingham; the subject haying heen introduced by the President, Mr. W. R. Hughes, in an address at the annual soirée of the Society. This Committee, after procuring information from different Aquaria in this country and on the continent, sent a deputation to visit and examine the Crystal Palace Aquarium and the Brighton Aquarium, fer the purpose of obtaining practical information about the requirements to be provided for, and specially to enquire into the two different systems of circulation and aeration of the water that are carried out at those places and the results of their working.
In the Crystal Palace Aquarium a constant circulation of the water is maintained night and day throughout the series of tanks, in connection with a large reserve of water in the store tanks, amounting to five times the contents of the show tanks; and the aeration is effected by means of small jets of water under considerable pressure, which are discharged into the top of each tank, and carry down mixed with the water of the jets a quantity of air, which is discharged in the form of countless myriads of bubbles, so minute that they float a long time about the body of the water in the tanks before rising to the surface, and thus present an enormous oxidising surface to the water; and, as a result, the whole mass has a bright, sparkling, almost effervescent appearance. In the Brighten Aquarium the aeration is effected by pumping air into the tanks through pipes of considerable size, from which the air issues in large bubbles that rise quickly to the surface; there is net any actual circulation of the water from one tank to another, and the quantity of water in the reserve tanks bears only a small proportion to that in the show tanks; the water can, however, be renewed, by pumping from the sea, but in consequence of the supply being taken from near the shore the water Is exposed to mixture with sand and other detritus, and requires same time to become clear, In the Crystal Palace Aquarium the original supply of sea water for the tanks continues in use, and does not require any renewal, except ta replace unavoidable waste. All that is needed being the addition from time to time of a small quantity of fresh water to compeusate for the gradual loss that takes place from evaporation; the supply of sea water in the store tanks—which are kept in the dark to counteract the tendency to vegetable growth in the water—is so much greater in quantity than the contents of the show tanks, that the water after circulating through them becomes thoroughly restored to a fresh end healthy condition before returning to the show tanks in the course of the circulation.
The result of the examination and enquiry of the Committee was a recommendation of the Crystal Palace system, (which is the plan of
