142 TREUBIA VOL. Ill, 2. 



The water outlet from the tanks takes place close to the bottom 

 through an earthenware pipe, 4 cm. internal diameter, which is built in 

 the middle of th*e tank towards the rear wall. 



This vertical earthenware pipe, which is open at top and bottom, ends 

 in a T piece at the top end, whose short horizontal leg pierces the rear 

 wall of the tank a few centimeters under the top edge. 



This short leg is connected to an earthenware elbow leading into an 

 earthenware down pipe, which runs outside against the rear wall of the tank. 



This latter pipe eventually opens out into the waste water duct, which runs 

 along the back of the tanks, (see Diagram), which we shall presently refer to. 



Inside the tanks the lower end of the earthenware outlet pipe is fitted 

 with an ebonite cover pierced by a number of small holes, which allow 

 the water to pass freely through ; this cover is easily removed by hand, 

 and its purpose is to prevent the entrance into the outlet pipe of small 

 fish, or other animals. 



It will be quite clear that this arrangement, which carries off water, 

 from the lower portions of the tanks, does not act as a syphon, but only 

 as an overflow. 



As has already been stated, an open reinforced concrete duct, covered 

 with fibro cement plates cut to size, runs in the accommodation ways under 

 and against the rear walls of the tanks. 



Round openings have been cut in the fibro cement plates to ad- 

 mit the vertical earthenware draw off pipes of the tanks, which pipes 

 project through to underneath the fibro cement covers. 



The smaller aquaria and hatching jars placed on the tables (3, 

 Plan No. 3) can also let their water flow off into this waste water 

 duct by means of rubber hose. 



The waste water ducts running behind the two rows of tanks 

 finally end close to the Eastern wall of the aquarium chamber. 



Just before this ending, the bottoms are pierced from under by an 

 earthenware pipe of 10 cm. internal diameter, which also passes through 

 the ceiling of the aquarium cellar. 



Both of these large earthenware pipes carrying off the waste water 

 of the tanks to the aquarium cellar, discharge into one of the two 

 extremities of a reinforced concrete duct which is suspended from the 

 roof of the cellar. 



This duct runs in a direction North to South, that is to say per- 

 pendicularly to the longitudinal axis of the aquarium building. 



In the middle of this duct is another opening through which the water 

 is carried off in an earthenware pipe of 10 cm. internal diameter; this 

 pipe branches off into two (see T' and T' in the top half of the Diagram). 



Just after this forking and in each of the two pipes resulting there- 

 from, is fitted a hard phosphor bronze valve, firmly cemented to the 

 connecting pieces of the earthenware pipe so as to be absolutely watertight. 



