94 



DISPLACEMENT INTERFEROMETRY APPLIED TO 



With these light swimmers the adjustment is remarkably precise ; but the ob- 

 served rates are relatively larger because of the small charge. 



The first experiments with A were made with a larger diver (M=*j.o2$ 

 grams, diameter 2.4 cm.); but this proved too sluggish in its motion within 

 the sheath EE and it was therefore soon discarded. The results are given 

 graphically in curves A (old), A '(new), andC, figure 112, g/m in ten thousands, 

 as before. C', after being installed, was left quiescent for over 10 days. It 

 appears, from the graph C, that the loss of air during this interval was almost 

 inappreciable. After resuming the measurements, April 6, a large rate at 

 once establishes itself. Practically the same is true for the diver A (fig. 112), 

 though from the viscosity of the sheet of water surrounding the diver the re- 

 sults are rough. Hence it is again shown that the chief cause of the air-losses 

 found is the partial exhaustion made to float the diver during observation. 



t\ 



<A 





w 



fov^ 



ou 

 113 



p 



Another interesting result for these sheathed divers is to be noted. In the 

 lapse of time (one or more weeks) it is found that the air escaping from a 

 in the diver, figure 113 (which at rest stands on the bottom of the vessel A A), 

 at first tends to accumulate at c at the top of EE. Air-bubbles not originally 

 present show themselves at c. In other words, the mechanism is such as to 

 admit of the gradual expenditure of the gravitational energy of low-lying 

 bubbles, so that they eventually reappear, in part at least, at c. Later, how- 

 ever, after weeks, these bubbles in turn gradually vanish at c. Comments on 

 the reason for this will be found in the earlier report (1. c., 74). 



The initial rates (r = , . time in days) of both after April 6 were 



g/m 



enormous : 



A', r =0.009 (per day) C, r =0.006 



After a week the rates of both change through an inflexion in each curve and 

 become 



A', r = 0.002 C, r 0.003 



