216 VICTOR E. SHELFORD AND W. C. ALLEE 



side to the bottom of boiler I. In this boiler, the water usually 

 reaches the boiling point before flowing into the receiving tank. 

 It flows out through double downward curved tubes K, to the 

 cooling coils under the pressure of a column of water of the height 

 of the delivery tank. The curves in the pipe in the coolers cut 

 down the pressure particularly in the lower cooler where the 

 pipe is 1^ inch, so that the flow from the outlet valve cannot 

 exceed 1200 cc. per minute. The treated water may be at the 

 exact temperature of the tap water and may contain as little as 

 0.3 cc. of oxygen per liter. If the water in the delivery tank falls 

 below the lower ends of the withdrawal tubes K and the coils fill 

 with air, the water does not flow. To clear the pipes of bubbles, 

 the hot or tap water may be forced through them by turning the 

 three-way valve beneath the delivery tube and opening valve 

 or the corresponding tap water valve. 



At all times of the year, but especially in the winter and spring, 

 the tap water from Lake Michigan is supersaturated with gases, 

 and in an open vessel the gases come off in bubbles which soon 

 cover the bodies of animals in experiments, and thus render their 

 activities abnormal. Fish kept in aquaria, which are supplied 

 with this water, die within a few days or even hours, from gas 

 disease. To remedy this and to supply water which is free from 

 excess gas, cold water is allowed to run through tjie apparatus 

 and is withdrawn from either the second or the third withdrawal. 

 The second withdrawal is supplied with a union by means of 

 which iron pipe may be attached to the aquarium in which fish 

 are kept, while the third is supplied with a hose-end near the 

 surface of the water table. With this apparatus we have been 

 able to secure water of any desired temperature and any desired 

 gas content, nitrogen excepted, within the limits and needs of 

 our problem. 



(1) Effect of the apparatus upon the water. Here we are con- 

 cerned with three things: (1) The normal tap water, (2) the hot 

 water, and (3) the water that has passed through the apparatus. 



(1) The cold water supply is from the Chicago water system 

 which uses water taken from Lake Michigan at a distance of 

 2^ miles from shore and from a depth of 6 feet where the water 



