40 



C. M. BREDER, JR. 



arranged to provide as little as a specified 

 number of drops a minute, and will main- 

 tain a surprising- accuracy if properly 

 designed. 



The overflow provided for tliis system is 

 a constant-level siphon. If such a siphon 

 is made by a glass blower, it will be expen- 

 sive, subject to breakage, and not readily 

 cleaned. A siphon can be made quickly 

 and cheaply of some straight glass tubing, 

 a tee, some flexible rubber or plastic 

 tubing, and two small strips of wood or 

 plastic. No dimensions are given, as 

 these will vary with the individual needs, 

 although figure 1 is drawn to scale. The 

 two strips of plastic are identical ; each 

 has two holes drilled in it to fit the glass 

 tubing snugly. The parts are assembled 

 to make a constant-level siphon attached 

 to the lip of an aquarium as shown in fig- 

 ure 2. The lower piece of plastic may be 

 fastened to the aquarium by small clamps 

 or may be cemented to it. The open, 

 upper end of the tee vents the siphon. If 

 a cap or plug is placed on this it immedi- 

 ately becomes a simple siphon and will 

 drain the aquarium to the level of its inlet 



tube. This is sometimes found to be an 

 added handy feature. The level of the 

 water in the aquarium will be that 

 at which the overflow water spills out 

 through the horizontal leg of the tee. Ad- 

 justments of this to a fine point may be 

 made by raising or lowering the tee 

 through the hole in the plastic support, or 

 tliis whole external assembly may be 

 moved up or down by altering the position 

 of the straight length of tubing which 

 passes through the hole in the other piece 

 of plastic connecting it with the tube in- 

 side the aquarium. By arranging the out- 

 side part, of the siphon to lie along the 

 aquarium wall, as shown, the danger of its 

 being in the way of operations is reduced. 

 Cleaning presents no problem with this 

 type of siphon. If something does never- 

 tlieless block the siphon tube from the 

 aquarium, it almost always can be cleared 

 by blowing into the open end of the tee 

 and restarting the siphon by drawing on 

 this same open end of the tee while the 

 outlet tube is held shut. It is possible 

 and sometimes more convenient to attach 

 the outer portion of the constant-level 



Figure 1. — ^Side and end view of constant-level siphon made up of sandard parts. 



