470 



Mr Edmonds, On Quasi-Radio-activity 



sulphuric acid jar, by means of the key F, a weighted dropping 

 brass rod W, enabling it to be earthed when necessary ; the other 

 pair of electrometer quadrants being earthed. 



The disc A was connected to one pole of the battery By, of 

 180 secondary cells, the other pole of which was earthed. 



For the majority of the experiments the needle of the 

 electrometer was kept at a potential of 40 volts, giving a 

 deflection of 200 scale divisions [mm. at 1 metre from the 

 mirror] for 1 volt difference of potential between the electrometer 

 quadrants. 



Fig. 1. 



A disc was taken and placed facing the points and subjected 

 to the discharge for an hour, after which it was disconnected, and 

 a powerful air blast caused to play upon it for 5 minutes to 

 remove any ions which might be in its neighbourhood. It was 

 then placed in the cylinder, the electrode B and its pair of 

 quadrants being earthed, and connected to the terminal of the 

 battery ; on insulating B a charge was communicated to it of the 

 same sign as the potential of A, and the electrometer needle 

 received a deflection which increased rapidly for the first few 

 minutes, but eventually became stationary at the expiration of 

 half-an-hour from the time at which B was insulated. 



Each of the discs in turn was thus tested, and the resulting 

 deflections all fell between the limits of 78 and 80 scale divisions, 

 being thus identical within the errors of experiment. 



On the face of each disc, after a discharge, was seen a deposit 

 which was darker at the places immediately opposite the points, 

 and very light at intermediate places. Tests made on this deposit 

 showed the presence of slight traces of iron when needles were 

 used as points, the " Prussian blue " precipitate being obtained, 

 while when other metals — copper, brass — were used, very faint 



