REACTIONS OF FISHES TO ATMOSPHERIC GASES 215 



return bend of f inch galvanized iron, with a third swing check valve (E) inserted 

 at the level of the float valve, to hold the weight of the water in the pipe, as the 

 float valves are not constructed so as to withstand back pressure. The valve F 

 is a tee handled valve with a brass bar 7 inches long bolted to the tee, a piece of 

 metal plate clamped to the pipes, lies directly behind the brass bar and the 

 position of the bar for 1200 cc. and 3600 cc. per minute under average pressure is 

 marked on the plate. Four | inch iron pipes are used to distribute the water 

 over the top sieve. The sieves are 18-inch garbage-can lids, with about 1,200 

 1 mm. holes punched in, 1 cm. apart. The collecting pan is of galvanized iron, 

 being also a garbage-can lid, a little larger than those mentioned above, with 

 8 I inch holes. Aluminum tubing | inch inside diameter is threaded into iron 

 nuts, which are soldered to the lid directly beneath the holes. 



The boilers, H and / are aluminum saute pans without handles, purchased from 

 the Aluminum Cooking Utensils Company. They are drilled and the drain pipes 

 are lock nutted into position. The pipe leading from the upper to the lower boiler 

 is of galvanized iron. The small perforated pipe is of brass. The delivery tank 

 is of galvanized iron but for durability an aluminum vessel should have been used. 

 The gas burner a is a water heater burner; h is made up of six small unit burners, 

 so that the amount of heat may be fully controlled; c is a gas range burner which 

 keeps the water in the delivery tank at the boiling point. The delivery tank is 

 supplied with an emergency overflow (Eo). The withdrawal tubes K and K of the 

 delivery tank are f inch galvanized iron pipe, which fits the smallest size three 

 way valve (3 Wv); (for withdrawals 2 and 3, see text). The first cooler contains 

 1.5 feet of block tin pipe f inch inside; the second cooler contains 60 feet of block 

 tin pipe, j^ inch inside. The tin pipes are soldered to brass fittings. The valve 

 (R), at the final outlet, is a j inch straight way valve. The coolers are supplied 

 with tap water through J inch iron pipe attached with unions. Valves 0, A", and 

 L, are J inch brass gas service cocks with tee handles. The coolers are made by 

 setting one galvanized iron tank into another, the pipe being fastened to the wall 

 of the inner tank. The overflows of the tank lead to a lead covered trough which 

 empties into the sink (S). The inner space in the lower tank, is intended to be 

 used as an ice pack in summer when a temperature lower than the tap water is 

 desired. 



The gas introducer A, is a brass chamber (cm.) with half unions on the ends, and 

 a plate glass front pressed against rubber packing bj' means of screws and a brass 

 frame. On its lower side are two small chambers (above Ch), which are connected 

 with the main chamber by very small holes drilled in the apices of small cones 

 hammered into the metal. Each small chamber communicates with a cock which 

 may be attached to a tank of gas. The pipes in the two coolers are connected with 

 the gas introducer by one-half unions. Many brass ground joint unions, where- 

 ever practicable, make possible the detachment of any part. The entire appara- 

 tus occupies a space above the table 97 by 130 cm., the highest part reaching to the 

 ceiling. It is supported on a frame of iron pipe made by screwing together cut 

 pipe and fittings described on pages 188 A-189 A, of Crane Company's catalog No. 

 40. The sieves are supported on wire pins placed in holes drilled through both 

 walls of the four pipes which make the tower. Because of the small space avail- 

 able and because the completed apparatus is the result of several experiments, 

 there are unnecessarj- complications. 



