ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



L09 



Apparatus for the Aeration of Aquaria.*— B. Jockel describes the 

 following arrangement (fig. 15) for aerating aquaria. The completely 

 closed cistern A is connected by the tube \Y with a water supply ; through 

 an opening in the top of A is passed a siphon tube H that reaches 

 nearly to the bottom, and has its free arm ending as low as possible 

 below the vessel ; a second opening in the top of A admits the tube L, 

 which is the commencement of the air supply which passes through the 

 bent tube L to the valve flask V, and air box W K, to the aquarium D ; 

 a third opening admits the open tube St. 



st 



^ 



cc 



■W" 



Fig. 15. 



When a constant stream of water passes into A the bottom of the 

 vessel will soon be covered, and when the lower openings of the tubes 

 H and St are closed then the connection of the inside of A and the air 

 present in the air supply tube with the outside atmosphere will be broken ; 

 water now begins to rise in the siphon tube H and in the tube St, and 

 continues to do so until the pressure is sufficiently great to overcome the 

 resistance at the outlet nozzle in D, and at this moment ventilation 

 commences. When the cistern A is full the columns of water in the 

 tubes St and H rise until the liquid tips over the bend of H and brings 

 into action the free arm of the siphon, whereby the vessel A is quickly 

 emptied, when it will be filled with air sucked in by the tube St ; the 

 process is then repeated. It is necessary that the upper end of St and 



* SB. Gesell. Naturf. Freunde, 1906 (Feb.) p. 66. 



