276 



U. S. BUEEAU OP FISHERIES 



The circulation of stored sea water through exhibition tanks and 

 of sea water into pools not connected with a reservoir is accom- 

 plished by mechanical methods that are not only expensive but re- 

 quire constant attention. Pumps driven by steam and gas engines 

 and by electric motors have been emjDloyed satisfactorily for this 

 purpose. The electrically driven pumps in use at the New York 

 Aquarium are rotary pumps that draw water from the reservoir and 

 from the harbor through 4-inch pipes. The water ends of these 

 pumps are of admiralty bronze. The electric rotary pumps used in 

 summer for circulating fresh water from the refrigerating tank have 



Fig. 17. — Fountainlike 



effect of aerated water 

 Aquarium 



in an exhibition tank. New York 



water ends of cast iron. All of these pumps are installed in dupli- 

 cate as a safeguard against accident. An additional rotary pump 

 is in use at times as an air compressor. 



The piping connected with the reservoir system is lead lined ; that 

 connected with the harbor system is of galvanized iron. The reser- 

 voir supply is distributed in a part of its course (the section passing 

 over the exhibition tanks) through a 4-incli line of hard-rubber pipe 

 installed many years ago. This material is ideal for the distribution 

 of water that flows by gravity, but it is expensive now. Piping of 

 pure or chemical lead is safe and serviceable for aquarium purposes, 

 especially in the smaller sizes. Iron pipe, lead lined, is expensive 



