THE MAEINE AQUARIUM 



65 



down into the aquarium, and then, hidden as much as possible by 

 the rockery, terminates in a very fine jet just above the level of 

 the water in the centre. The upper vessel should also be provided 

 at the top with a .loose covering of muslin to serve as a strainer, 

 and this should be replaced at intervals as it becomes clogged with 

 sedimentary matter. 



In order that this arrangement may give perfect satisfaction 

 the two vessels (c and v) must each be of at least half the capacity 



Fio. 38. METHOD OF AERATING THE WATER OF AN AQUARIUM 



A, aquarium with fountain ; c, cistern to supply the fountain ; o, pipe for 

 overflow ; V, vessel for overflow 



of the aquarium itself, and the total quantity of salt water sufficient 

 to fill the aquarium together with one of them It should also be 

 remembered that since the pressure of water depends not on its 

 quantity, but on its height measured perpendicularly, it follows 

 that the height to which the fountain will play is determined by 

 the height of the vessel c above the level of the jet. 



Let us now suppose that the aquarium and the upper vessel 



