THE PUBLIC AQUARIUM 



275 



quiet except for the movement of the livintj: exhibits. It also simpli- 

 fies the work of inspection during the hourly examination of the 

 tanks at night, the water flow being visible. 



Such aeration is accomplished by perforating the supply pipe at 

 a connection a few inches above the surface of the water and insert- 

 ing a 2-inch tube of slightly smaller diameter in the manner shown 

 in the accompanying diagram. Without the smaller tube the air 

 would rise to the surface in use- 

 less large bubbles: with it the air 

 escapes in a way that gives it the 

 appearance of a fine white mist. 

 Liberated into the bottom of the 

 tank in this way the air carries 

 with it to the surface the finer par- 

 ticles of dirt in suspension, which 

 float off through the overflow 

 pipe. In some European aqua- 

 riums the water is supplied at the 

 surface by a strong jet directed 

 into a pipe leading to the bottom, 

 where the water escapes finely 

 aerated. The same effect may be 

 produced by plugging the outlet 

 of an air pipe with porous wood, 

 preferably linden, through which 

 the air from the compressor es- 

 capes as a " mist " visible every- 

 where in the water of the tank. 

 In the aquarium at Washington, 

 T>. C, " filtros " plugs are used in 

 air pipes, being less likely to be- 

 come swollen and clogged. 



Aeration in this way is more ef- 

 fective than through the water 

 pipe, but it necessitates the contin- 

 uous operation of the compressor. 

 In the New York Aquarium the 

 air compressor is seldom used ex- 

 cept when pumps are stopped and 

 water flow is cut off temporarily. 

 At such times mechanical aera- 

 tion is imperative until the flow Fio. 16. — Aerating device, showing position 



of water is restored. ^Lvf waiter letl '"^^''''^''^ ^"^^'^ "^'^^ 



PUMPS, PIPING, AND VALVES 



The circulation of fresh water in an aquarium is accomplished by 

 simple and easily arranged methods. The supply derived from the 

 city water system flows through either pressure or gravity filters 

 into elevated distributing tanks, from which lead the lines of piping 

 that carry it to the exhibition tanks, whence it is drained to the 

 sewer line. Galvanized piping in all sizes is satisfactory for the 

 distribution of fresh water. That in the New York Aquarium is 

 still in use after 30 years of service. 



