346 



GASOMETRIC-MANOMETRIC METHODS 



The distance between the top of the diver, when the diver is at 

 the bottom of the vessel, and the circular mark (H) on the vessel 

 should be only a few mm. in order to minimize the movement of the 

 neck seals. The hydrostatic pressure on the diver should be kept 

 small; accordingly, the level of the medium should not be higher 

 than G in Figure 113. 



Fig. 113. Flotation vessel. 



A, ground-glass joint 



B, brass block 



C, supporting rod (in cross section) 



D, brass rod 



E, brass cuff 



F, wing screws 



G, surface of flotation medium 

 H, circular mark. 



From Holier (1943) 



The flotation vessels are mounted by means of B (Fig. 113) on a 

 brass rod running the length of the thermostat. 



Observations of the diver may be facilitated by using a magnify- 

 ing glass or a low-power horizontal microscope mounted so that it 

 can be moved sidewise on a rail fastened to the outside of the 

 thermostat. With this arrangement the microscope can be shifted 

 for use with divers in the different flotation vessels. If the eyepiece 

 has a horizontal cross hair, this can serve to establish the equilib- 

 rium position of the diver; in this case the circular marks on the 

 vessels are superfluous. 



(3) THE FLOTATION MEDIUM 



The flotation medium originally used by the Carlsberg Laboratory 

 workers was an almost saturated solution of ammonium sulfate, and 

 the Cambridge group employed an 11 A^ solution of lithium chloride. 



