610 AQUARIUM and the renewal of the water is difficult, it may be revivified by dipping out and pouring back in a small stream from a proper height. As in the marine tank, an excess of sunlight is apt to encourage the growth of a minute green fungus, besides unduly elevating the tempera- ture, which should range between 40 and 60 F. The marine tank, owing to its greater range, and the extreme sensitiveness of its ani- mals and plants, requires more constant and careful management. As a rule it should be more shallow. To secure this, and also obtain suffi- cient depth of water for fish and hardy plants, a tank having its back and two ends opaque has been successfully adopted, in which case these may be of the same material as the bed plate marble, slate, or well seasoned wood. The front is of glass, and the bottom an inclined plane rising from the lower corner in front Marine Tank, Side View. to above the water level behind ; on this rest the rock and shell work. The triangular space between the front and this plane may be filled to the depth of an inch or two with sand and gravel, with a sprinkling of the same among the rocks and shells above. The purpose of this sloping floor is to afford the anemones, actiniae, &c., which move seldom and slowly, to ap- proach the surface and recede from it at pleas- ure. Marine plants purify sea water, as fresh- water plants purify fresh water. The difficul- ties of maintaining the balance are, however, greater in sea-water artificial tanks than in fresh-water ; but by care in selecting seaweeds, avoiding those which are large and throw off much matter from their surface, and not over- crowding the water with animal life, tanks containing marine aquatic animals and plants can be easily managed. Species of porphyra, chondrus, crispus, iridea edulw, and the delet- serice are recommended. Where vegetation is only needed for the production of oxygen, Mr. Shirley Hibberd, the author of a useful hand- book on the aquarium, recommends the en- couragement of confervoid growth ; and where sea water is used, the germs contained in it will soon, under the light and warmth of the sun, develop into a vigorous and serviceable vegetation. This, together with certain ani- malcules that, contrary to rule, are also oxy- gen producers, will be all that is needed to preserve the desired balance. The absence of direct sunlight and the presence of the bucci- num or sea snail both serve to keep in check that fungous or mucous growth which would otherwise obstruct the vision. The fishes and crustaceous and molluscous animals should be introduced by degrees, with proper regard to maintaining the due balance of vegetable and animal life. Those which appear to thrive best are minnows, sticklebacks, shrimps, small lobsters, hermit crabs, eels, and star fishes. The patella or limpet, purpura or whelk, the top, the winkle, and several varieties of crepi- dula also do well. The more delicate sea plant-, with the various forms of actinia-, should be secured if possible attached to their native bed, as removal from it is hazardous. The best position for either tank is between or at the side of windows, so as to avoid the direct rays of the sun. Marine animals and plants are extremely sensitive to atmospheric changes, and the salt water, which should not vary far from 60 F., should also have a specific gravity of 1'028 at this temperature. As in the fresh-water aquarium, regard must be paid to the habits and tastes of the inmates, lest the stronger overcome the weaker. All save the fishes may be best transported in damp sea- weed, care being taken to pack securely and transfer rapidly. Where sea water cannot be obtained, a mixture of common salt 81 parts, Epsom salts 7 parts, chloride of magnesium 10 parts, and chloride of potassium 2 parts, may be dissolved in pure water until its gravity reaches 1 -028 at 60 F. The animals should be fed twice a week with finely cut fresh mus- sels, oysters, or raw beef; and in case of the mollusks, actiniae, &c., the food should be brought within reach by means of a small glass rod. Decayed vegetation or putrid ani- mal matter must be quickly removed. When the supply of oxygen is limited, the fishes will approach the surface often to breathe. The first aquarium having for its aim the instruc- tion of the people was erected in the gardens of the zoological society, Regent's park, Lon- don, in 1853. It was made up of 25 glass tanks, 6 feet in length and 30 inches in depth and width, lining the interior of a crystal building 60 by 25 feet. The success of this effort prompted the crystal palace aquarium company to erect their building, which was opened to the public Aug. 22, 1871, at Syden- ham. This mammoth aquarium with its ad- juncts is nearly 400 feet long and 70 broad.
