EIGHTH ANNUAL REPORT. 75 



The large floor pool in the center of the building can now be 

 provided with attractive exhibits. Heretofore it has been too dark 

 to permit of its contents being seen, except on the very brightest 

 days. There is now no reason why it should not contain some 

 of the large-sized marine animals, for which it was intended. 



It should be borne in mind that the perfect lighting of the 

 Aquarium is a matter of considerable difficulty. The building is 

 an old fort, with walls 8 to 10 feet thick, in which it is impractica- 

 ble to make alterations. The light in the lower wall-tanks being 

 derived entirely from lofty skylights, is still somewhat like the 

 light at the bottom of a well. 



Reservoir for Sea-Water. — The pressing need of the Aqua- 

 rium has always been pure sea-water. The collection of sea ani- 

 mals has suffered from being kept in the brackish or nearly fresh 

 water of New York Bay, which has always been used. Not only 

 has the loss of marine specimens been great from their being kept 

 in water that was too fresh, but the exhibition of many marine 

 animals has been quite impossible, for the same reason. A still 

 greater objection to its use is its muddiness during the winter 

 months. The constant heating of water in winter has always been 

 very expensive. With a suitable reservoir four important objects 

 will be attained: first, clear instead of muddy water; second, 

 salt instead of brackish water ; third, the exhibition of new forms ; 

 fourth, the saving of heated water. 



The construction of a reservoir has been undertaken with con- 

 siderable hesitation, as the Aquarium has no basement and it is 

 necessary to locate the reservoir in the Park adjacent to the build- 

 ing, placing it entirely underground. This is a difficult matter, 

 as the tide at the adjacent sea-wall rises considerably above the 

 floor of the reservoir, making its position, on account of the lift- 

 ing power of the tide, a rather unfavorable one. 



There will probably be no difficulty in filling the reservoir with 

 pure water, as numerous steamships come to New York with sea- 

 water in their water-ballast compartments. 



This reservoir or closed-circulation system is the one common- 

 ly used in the public aquariums of the world. 



In the table of temperatures and densities presented elsewhere, 

 the mean temperature is shown for each month. While the aver- 

 age for February was 37 , it was frequently as low as 35 . The 

 energy expended in raising the water temperature to the neces- 

 sary warmth of 70° is considerable. The waste is a continuous 

 one. As there is no reservoir for receiving the warm water, it 

 has always flowed back to the Bay. The completion of the reser- 



