282 



tJ. S. BUREAU OF FISHERIES 



numerous 2-inch holes along the upper side, thus distributing its 

 fall more widely. The filters being in two sections, the sand bed in 

 each can be cleaned in turn, the other temporarily carrying all the 

 water. Cleaning is effected by closing the top or supply line until 

 the filter is drained, when the bottom line is closed and the fiow 

 reversed by admitting fresh water at the bottom until all waste 

 matter on top of the sand bed has overflowed into a sewer line. The 

 fresh water is then drained off to the sewer, the sea water turned 

 on, and the filter again put in operation. The sand bed in each 

 section is 2 feet deep, of No, 8 cut quartz. To facilitate cleaning, 

 four small and finely perforated air lines of lead pipe across the 

 bottom are connected with an air compressor. When the flow is 

 reversed and the compressor put in operation the combined lifting 

 power of water and air serves to stir up and 

 clean the sand bed. Each section of the filter 

 is 10 feet long by 6 feet wide. The saw cuts 

 in each branch average about two per inch 

 run. The Jackson Filter Co., of St. Louis, 

 appears to have passed out of existence. 

 Other aquariums using this type have copied 

 that in the New York Aquarium. 



FILTERS FOR FRESH WATER 



The two bronze pressure filters that have 

 always been in use at the New York Aqua- 

 rium are cylindrical in form and measure G 

 feet in diameter and depth. The bottom in 

 each filter is fitted with 80 closely set strainer 

 heads with minutely perforated copper caps. 

 The quartz sand bed in each is 4 feet deep. 

 All fresh Avater used in the exhibition tanks 

 and pools of the aquarium passes through 



Fig. 21.— Lead filter pipe fUoco f^Uora 



with saw cuts tuese niteis. 





VENTILATING SYSTEM 



In a building sometimes of peculiar construction, like that of an 

 aquarium, and often crowded with visitors, artificial ventilation fre- 

 quently is necessary. The air circulation in the New York Acjuarium 

 is provided by a 6-foot motor-driven fan, drawing air through a 

 wire-screened window. The air passes through a stack of steam- 

 heated coils, the steam being cut oft' in summer. It is distributed 

 through large, galvanized, sheet-iron ducts suspended under the 

 balconies on each side of the building. The ventilating system is in 

 operation only during the hours when the building is open to the 

 public. 



COLLECTING THE SPECIMENS 



Large fishes are difficult to transport as well as to catch. Tanks 

 containing sufficient water to keep them alive during shipment are 

 enormously heavy, and, as water animals can not endure the delays 

 of freight service, the bills for expressage are large. Very few living 

 fishes can be shipped without attendance. They must be " personally 



