RIVER GARDENS ; 



water. Sea shells, or corals, so often used for this 

 purpose, have a very anomalous appearance, and de- 

 stroy the natural character of the whole arrangement. 



The kind of water is not very material, if the 

 balance of animal and vegetable life, after added, be 

 nicely adjusted, and not introduced too profusely. 

 A few cautions, however, are necessary. Water 

 that has been boiled would not do ; in fact, fish will 

 live but a very short time in boiled water, because 

 in that operation the greater part of the oxygen has 

 been expelled from it. The water of chalybeate 

 springs is likewise unfit, as the salts contained in it 

 are very injurious to vegetation. River water is 

 best, but pump or well water will answer very well, 

 especially if well aerated, by pouring from one 

 vessel to another before used. 



The water in the tank may be occasionally 

 aerated, also, by means of a common pair of bellows 

 with a piece of gutta-percha tubing attached to the 

 end of the pipe. A contrivance of this sort is 

 adapted for all the tanks at the Dublin Zoological 

 Gardens, with branch pipes leading to each separate 

 tank, so that one pair of bellows aerates the whole 

 series. The action of the air, as it enters the vessels 

 from these tubes, is said to produce a very pleasing 

 effect, insomuch that Dr. Ball, when he described 



