1883.] Electric Discharge with Chloride of Silver Battery . 297 



Fig. 8. 



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^H^' 



p 



The authors remark that one cannot but be impressed, from the 

 experiments described in the paper, and others in their former papers, 

 by the apparent plasticity of the aggregate assemblage of molecules 

 constituting a stratum which yields to external influences that 

 modify its form. 



The authors describe and figure a case of complex strata in the form 

 of an outer bracket convex towards the negative (fig. 9) , and close to it 



Fig. 9. 



an inner chord; also discharges in various gases in tubes of large 

 dimensions, 37 inches (94 centims.) long and 5^f inches (14'8 

 centims.) diameter. In these the stratification, which is compara- 

 tively narrow at the terminals, extends in a conical form from the- 

 terminals to the full diameter of the tube. 



They have found that the dark space in the discharge in vacuum 

 tubes is only relatively actinically dark in comparison with a stratum,, 

 and they succeeded in obtaining a photograph of the dark space in 

 thirty-five minutes as strong as that from a stratum in two and a-half 

 seconds ; consequently they conclude that the dark space is 840 times 

 less actinically bright than a stratum. 



The authors next describe a number of experiments, by means of a 

 Thomson-Becker electrometer used on a method, to avoid leakage, 

 proposed to them by Professor Stokes, to ascertain the difference of 

 potential in different parts of a vacuum tube having a number of 

 rings sealed within it, also in other tubes of special construction. 

 These bring out instructive information in reference, not only to the 

 relative resistances of different lengths of a column of gas at various 

 pressures, but also forcibly to the impediment presented by the 



