258 U. S. BUREAU OF FISHERIES 



the past 25 years. The building, a 100-year-old fort, has been 

 criticized as unsightly until altered by recent improvements. Its 

 extensive and varied exhibits alone constitute its unfailing attraction 

 for the people. 



The vital point to be insisted upon in planning the building is 

 that there should be skylights of ample size above the tanks of water 

 containing the exhibits. 



EXHIBITION TANKS 



The collections of the public aquarium, with the exception of a few 

 large forms kept in open pools, are exhibited in large stationary tanks 

 of masonry or wood, with glass on one side only — the side fronting 

 on the hall or corridor open to visitors. The tanks are built in rows, 

 end to end, thei-r glass fronts being in line with the wall inclosing 

 the public hall, their rear sides extending backward into the service 

 passage used by the caretakers. The visitor facing the glass front 

 sees the interior of the tank only, which is lighted from above. The 

 public hall receives no light from the skylights that illuminate the 

 tanks, being kept rather dim in contrast with the well-lighted tanks 

 containing the exhibits. 



An aquarium having a darkened public hall with well-lio;hted ex- 

 hibition tanks, such as that of the London Zoological Society, per- 

 mits very satisfactory views of the living exhibits. Such an interior 

 arrangement would be impracticable in an always free aquarium like 

 that of New York City, however, where the Sunday attendance alone 

 frequently exceeds 20,000 persons. 



Glass-fronted exhibition tanks, as constructed in the few aquariums 

 existing in this country, are of rather limited size, the inside dimen- 

 sions of the larger tanks averaging perhaps 6 by 6 feet, with a water 

 depth of 4 feet. In European aquariums they are usually somewhat 

 larger. Most of the tanks in the New York Aquarium have been 

 enlarged recently, the rear walls having been moved backward 11 

 feet from the glass fronts. This is about as far back from the the 

 glass as objects 'in clear water can be seen distinctly. Large tanks 

 permit the exhibition of more specimenis, while the increase in water 

 space greatly improves the conditions under which the occupants live 

 in captivity. Glass-fronted tanks of smaller size, such as those occu- 

 pying the balcony in the Ncav York Aquarium, are desirable for 

 invertebrates and are satisfactory for small and inactive vertebrates, 

 but most fishes (and these constitute the bulk of the exhibits of the 

 average aquarium) -need swimming space. Large fishes should not 

 be kept in small tanks, where they find neither room for exercise nor 

 the display of their habits and activities. 



All exhibition tanks in an aquarium must be supplied with strain- 

 ers of some sort in their top overflows and bottom drains to prevent 

 the escape of small fishes and the clogging of waste pipes with various 

 substances. In salt-water tanks, where metal and wire strainers rust 

 quickly, their renewal involves considerable expense. Strainers made 

 of lead or rattan have obviated these troubles. Several types are 

 shown in Figure 6. 



