44 



C. M, BREDER, JR. 



Figure 5. — Diagram of interaction between float valve and constant-level siphon. 



represents level of water in aquarium and siphon arm. 



y 



Dashed line 



cedures to add chemicals to an aquarium 

 at a prescribed rate by inactivating the 

 float and fixing the rate of flow by hand. 

 It also could be used to bring the concen- 

 tration of some chemical to a fixed limit 

 and then hold it at that point in flowing- 

 water aquariums. The water supply 

 would operate as above described and a 

 second float valve regulated to add much 

 less chemical than the water flow would 

 move with it and act as a follower to the 

 other if there was any fluctuation in tlie 

 flow of water, thus holding the additive in 

 proportion to the change of water. Also 

 a single float could be arranged to operate 

 the two valves in proportion to the setting 

 of each. 



While the designs of these float valves 

 have varied from time to time, all have 

 embodied the same principles as herein 

 described. The first and somewhat primi- 

 tive one has, at this writing, been in serv- 

 ice continually for more than 4 years and 



is still entirely satisfactory and depend- 

 able. 



CLOSED SYSTEMS 



The term "closed systems'' refers to cir- 

 culating systems in which the water is re- 

 turned to the aquariums after filtration or 

 other treatment and none is allowed to run 

 to w^aste during normal operations. Some 

 such system is mandatory for the mainte- 

 nance of marine forms remote from a 

 ready supply of sea water, and often con- 

 venient or necessary for various experi- 

 mental procedures involving fresh-water 

 aquariums. This is especially true of 

 cases where it is necessary to maintain 

 close control of some feature such as tem- 

 perature, chemical quantities, and the like. 

 By use of such means it is possible to 

 maintain a series of aquariums with abso- 

 lutely identical water conditions, as the 

 water in all is part of a common body. 

 Consequently no matter what transpires 

 in one aquarium there is no opportunity 



