of 157 llis. to the sijuare iucli. The air is tlieii carried to tlie hacks of the tanks, and lieing 

 taken down to the bottoms in f;ntta-i)crclia pipes, is seen by the visitor to rise in tiny silvery 

 l)uV»bles to the surface. This constitutes a vital principle, and if the supply of air is stopped 

 for half-au-liour all the fish in tlie tanks will be seen to be distressed, and in a short time would 

 rise to tlie surface for air and die. The reason of this is obvious. The fish breathe througli tlieir 

 (;-ill8, and roli the water in winch they are of its oxygen, which has conseipiently to he artificially 

 supplied to keej) them alive. 



In establislung Aquaria, the great difficulty iias always been to reguhite the sujiply and 

 demand of oxygen in the water. In small Aquaria this can be accomjdisiied liy iidjustiug the 

 -]iroi)ortiou of animal and vegetable life. The water ])lants and sea-weed give off the oxygen whic'h 

 is tlie life of the fish, and consume the deleterious carbonic acid gas. In large public Aquaria, 

 however, it has been found preferable to employ systems of artificial aeration. This may be 

 accomplished in several ways— by a constant flow of water ; by the water being driven into the 

 tanks, so as to impinge on the siudace, and carry down minute air jiarticles ; by keeping up a 



constant motion in the surface of the tanks, as by 

 having a small water-wheel revolving and lifting the 

 surface water continuously ; or by forcing direct 

 volumes of air into the tanks. This latter system 

 has lieen ado]ited at this Ai|uariunias the most economi- 

 cal and least likely to sto]i]iage or derangement, wliilst 

 under its use it is piossible to maintain the true 

 character of an Aquarium, that is, the employment ot 

 certain quantities of sea-water which are stored and 

 renewed from time to time, the actual waste being 

 reduced to a minimimi. 



Any jierson wishing to commence a maiine Aquarium 

 on a scientific jirincijde, in which zoophytes and tlie 

 lower forms of marine life may be kept, can do so very 

 easily by getting a glass dish about the size of a wash- 

 hand basin, placing on the bottom sand and a few 

 stones covered with sea-weed growth, the specimens 

 desired to keep, and a comjilete aeration c.m be secured 

 by filling and emjitying a glass syringe full of the 

 water several times a day, injecting sharply at a dis- 

 tance of, say, 6 inches from the sm-face, by which 

 means enough air is carried intf) the water to keep it 

 fresh and in a natural condition. 



In fact, in an Aquarium it is necessary to simulate 

 the action of the sea, where the constant action of the 

 waves and tides acting under natural laws is absolutely 

 necessary to prevent tiie stagnation of the ocean. 

 In several of the Euro})ean A([uaria artificial sea-water has been itsed with varying success, 

 prepared according to the following foiinula : — ■ 



Common salt 

 Kpsom salts 



si p.irts I Chloride of magnesium ... ... 10 parts 



7 ., Chloride of potassium ... ... 2 ,, 



is naturally preferable, and is always used where it can be 

 iive the comjiosition of sea-water according to analysis : — 



!I(J4744 Gypsum or sulphate of lime ... 1'407 



Carbonate of lime 

 Unaccounted for 



The real sea-water, however, 

 ohtaiiicil. It may he interesting to 



Water 



Common salt or chloride of .sodium ... L'7'0.')!) 



Chloride of magnesium .. ... .'J'tiGfi 



Chloride of potassium ... ... 0'7ti5 



Bromide of magnesium ... ... 0'029 



Epsom salts or sulphate of magnesium 2295 



The last-mentioned comjiouent jiarts occur in infinitesimal quantities in both sea 

 fresh water, and are therefore not usetl in protlucing the artificial fluid. 



0033 



002 

 1000 000 



