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Mr. A. Fleck on the Condensation 0/ 



similar to that already discussed (page 348) and shown in 

 fig. 6, namely, the alteration in the behaviour of the tube 

 in successive measurements. During the course of the 

 experiments three exposures of the tube were made at liquid- 

 air temperature, and it was noticed that the quantities of 

 emanation obtained in the experimental end (after all cor- 

 rections had been made) became smaller as time progressed. 

 When these quantities were plotted against the time, it was 

 found that in both cases the points lay on a straight line as 

 shown in fig. 11. It is further observed that the same per- 

 centage decrease is obtained in both cases. This is an im- 

 portant observation, and if it could be confirmed, it would 

 be strong indirect evidence that these emanations are non- 

 separable by condensation. This introduces an uncertainty 

 but, from the fact that the points in fig. 11 lie on straight 

 lines, it was considered justifiable to correct for this by 

 reading off the values for E L and G L at intermediate times 

 from the curve (fig. 11). 



Fior. 11. 



Points jot Radium arc m&rkcd. O. Thoriu m howti are shown %. 



Curves showing progressive change of the proportions of emanations condensed 

 at liquid-air temperature in the same tube with lapse of time. 



Results, — The different fractions obtained at various tem- 

 peratures are shown in the accompanying table, and also 

 numbers to indicate the order in which the experiments were 

 made. It is at once seen that at any temperature the frac- 

 tion of radium emanation condensed is greater than the 

 corresponding fraction for thorium emanation. Viewed as a 

 whole, this is the only result that can be arrived at, that 

 radium emanation appears more easily condensed than 

 thorium emanation. When more fully examined, however, 

 the points separate themselves into two lots each of which 

 lies on a curve. These curves have been separated and are 



