THE RESPIRATION APPARATUS. 



21 



resistance. No valve that we could find on the market would be guar- 

 anteed by its manufacturers to meet these conditions. The form of 

 valve finally used is shown in figure 10. 



The valve consists of a mechanical closure which is subsequently 

 bathed in mercury, thereby giving a mercury seal. Air from the 

 blower enters the tube /, passes around the annular space s to the valves, 

 through the annular space a of the open valve, up through the vertical 

 tube b, and then to the absorbers at d. Figure 10 shows the valves as 

 in actual operation, one being open, the other closed. 



FIG. io. Mercury Valves. By raising the mercury reservoir the mechanical closure made by the 

 valve against end of tube b can be bathed in mercury. Direction of air current indicated by 

 arrows. The valve at right is open, that at left closed. Tube G is inserted in mercury and 

 is used for testing the system. 



To close the valve, the lower end of the tube b is shut off mechan- 

 ically by pressing an iron disk, in which a fiber gasket g is inserted, 

 firmly against its edges by means of the screw and spindle c. The 

 closure is then made complete by immersion in mercury. The glass 

 reservoir / is so raised that mercury can flow through the rubber tube 

 m into the annular space a until the level desired is reached. 



To prevent leakage of air along the spindle, it is caused to traverse 

 a length of pipe, the lower end of which is closed with a stuffing- 

 box and gland n t and the annular space between the spindle and the 



