TELE TALON, IEEE SEAL 22 
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are as follows :—Advantage is taken of the current of water which 
is brought by the pipe which waters the Bois de Boulogne. This 
water is under great pressure, and is brought to act upon air con- 
fined in an inverted cylinder. This air is admitted into another 
cylinder below the level of the aquarium, in which is some sea- 
water; this it forces up with great power into each of the reser- 
voirs, which it enters by a little jet. The compressed sea-water 
contains a great deal of air, which it carries with it into the reser- 
voirs. A pipe in the corner of each carries off the overflow into a 
well-packed carbon filter, from whence it passes into an under- 
ground reservoir, made of iron, lined with gutta-percha. From 
this the water is returned into the closed cylinder; is submitted 
again to the pressure of the air, and is again injected into the 
aquarium. The cylinders, being all underground, keep a uniform 
temperature of about 16° Cent., which is nearly the general 
temperature of the sea. In winter the walls of the aquarium are 
artificially heated. By means of a very simple contrivance in each 
reservoir the quantity of water can be diminished, and the ebb and 
flow of the sea thus imitated. At the same time, by considerably 
lowering the level of the liquid, certain creatures can be periodi- 
cally exposed to the air. In this circulation and movement of the 
water, its volume is diminished by evaporation, and the inorganic 
matters remaining in the liquid, at last it would become too salt. 
To remedy this, by means of a special apparatus, a certain quantity 
of rain water which comes from the roof of the building is passed 
into the great reservoir. An hydrometer indicates the time when 
this addition of fresh water is necessary. 
