22 THE WORLD OF THE SEA. 
certain degree the motion of the waters and their continual aération, 
a means has been devised by which water is added in a constant 
stream, entering the aquarium either in a fine jet, or drop by 
drop, whilst the overflow is conveyed away by a waste-pipe. It is 
requisite to build in the reservoir a miniature rockery of stones and 
pipes, in order that those creatures who shun the light may have 
a retreat ; or a screen may be used, which may be a piece of board, 
or asheet of cardboard, or a piece of cloth or ground glass. 
Small holes are made in the screen, through which may be seen 
what is going on inside, and by this means the animals may be 
observed without being disturbed, and we can learn all the details 
of their domestic life. It is beneficial to fit a cover to the aqua- 
rium, which prevents the creatures from getting out either by 
jumping or crawling, and also which preserves the dust from falling 
into it, which otherwise would collect on the surface and sink down 
through the water. 
In 1853, Mr. Mitchell, the Secretary of the Zoological Society 
of London, constructed an aquarium in the Zoological Gardens, 
Regent’s Park, of a size previously unattempted. The success of 
this little museum of sea life produced in England quite a 
sensation. The largest, the most beautiful, and the most com- 
plete of aquariums up to the present time, is that constructed in 
the Zoological Gardens in the Bois de Boulogne, at Paris. It 
was inaugurated on the Ist of October, 1861. The building is 
solidly constructed of stone, forty yards long and ten broad, 
showing a range of fourteen reservoirs, of Angers slate, facing the 
north. These reservoirs are nearly cubic, and have a front of 
strong glass, through which the interior can be examined. It is lit 
from above, by which a greenish, uniformly dispersed twilight, is 
secured, which is an exact imitation of the feeble light which illu- 
mines the submarine world. [Each reservoir contains about 160 
gallons of water, and in each is a rockery picturesquely arranged in 
the form of an amphitheatre; upon these rocks spread and grow 
different species of aquatic plants, the floor is shingled with pebbles, 
gravel, and sand, which affords sufficient cover for many animals. 
Ten of these reservoirs are appropriated to marine animals. The 
quantity of water used is about 4,000 gallons; it is never changed, 
but is continually flowing. The means by which the flow is secured 
