40(6 Mr, R. Warington, [March 27, 



waters it has reached as high as 38 per cent. This oxygen, by the 

 process of respiration, is converted into carbonic acid gas, or 

 mephitic air, the choke damp of the coalpit, a gas highly poisonous 

 to animal life ; but here comes into play that beautiful and won- 

 derful provision which, by the action of growing vegetation under 

 the influence of the sun*s light, converts this baneful agent into 

 vital oxygen, the *' breath of life." 



Water, fresh and marine. — The water used for the aquarium 

 should be clean, and taken direct from a river, or from a soft 

 spring, and should not have been purified by means of lime. 



As regards sea water, it should, if possible, be taken at a dis- 

 tance from shore, and at the period of high water. If artificial sea 

 water is employed, it should be made either from the saline matter 

 obtained by the evaporation of sea water,* or by the following 

 formula : — 



Sulphate of Magnesia . . 7^ oz. 



„ Lime .... 21 „ 



Chloride of Sodium . . . 43i „ 



„ Magnesium . . 6 „ 



„ Potassium . . 11 ?, 



Bromide of Magnesium . . 21 grains. 



Carbonate of Lime ... 21 „ 



These quantities will make ten gallons. The specific gravity of 

 sea water averages about 1*025 ; and when from evaporation it 

 reaches above this, a little rain or distilled should be added, to 

 restore it to the original density. 



Vegetation. — The plants best fitted for fresh water are the vallis- 

 neria spiralis, the myriophyllum, ceratophyllum, and the anacharis, 

 all of them submersed plants, and fulfilling the purposes required 

 most admirably. From the great supply of food in the aquarium, 

 the growth of the vallisneria is very rapid, and it requires, there- 

 fore, to be thinned by weeding ; this should never be done until 

 late in the spring, and on no account in the autumn, as it leaves 

 the tank with a weakened vegetation at the very time that its 

 healthy functions are most required. 



The vegetation of the ocean is of a totally different character 

 and composition, being very rich in nitrogenous constituents. There 

 are three distinct coloured growths, — the brown or olive, the green, 

 and the red. For the purposes of the aquarium, where shallow water 

 subjects are to be kept, the best variety is the green, as the ulvae, 

 the enteromorpha, vaucherise, cladophora, &c. These should be in 

 a healthy state, and attached to rock or shingle when introduced. 



♦ This is prepared by Messrs. Brew and Schweitzer, of 71, East Street, 

 Brighton. 



