(709 ) 



Both plates were I'ouiid, had a diameter of about 25 cm., were 

 insulated and motmled at a distance of about 2 cm. from each other; 

 the laboratory-battery (tf about 60 Volts and a resistance of 1 Megohm 

 were inserted in (he circuit from the galvanometer (jr to the plates. 



1 Me<'uhjTi, 



rliP'--Hl-^ 



A 



A. 



Fig. 1. 



The sensitiveness of the galvanomeler was adjusted at 1 inm. 

 deflection for 2X^^^"'^ Amp., the time required for a deflection 

 being about 5 to 7 seconds. Now a round plate, covered over a 

 diameter of about 20 cm. with powdered nranium-trioxide (containing 

 water) was shctved in between A^ and A^ and laid on A^. The 

 galvanometer now showed a deflection of 2.5 mm. As soon as the 

 nranium-))reparation was removed it pointed exactly zero again. 



The uranium-|)reparation was in this Avay repeatedly brought between 

 tlie plates of the coiidenser and taken away again and each time 

 the galvanometer showed the same deflection of exactly 2.5 nnn. 

 Each measuremenl was made in from 5 to 7 seconds; since, as has 

 been shown before, a deviation of 0.1 mm. can slill be noticed, the 

 probable erroi- of the observations may l)e pul at 4 per cent. 



The current measured amounted to 5X 1^^~^' Amj)., a value of 

 the same order as that calculated by Mrs. Curik for other uranium- 

 compounds which had been examined ujidei' similar circumstances 

 by means of the piezo-electrometer. 



We \\'\\\ briefly mention some ex}»eriments with a few milligrams 

 of a i-adium-salt. When the radium was placed between the condenser 

 plates, a P. D. of 2 Volts proved sufficient to deflect the image of 

 the wire a few centimetres. With a P. ]). of 40 Volts in the circuit 

 the same eli'ect coidd be obtained by holding (he radinm-pre])aration 

 at a distance of J metre from (he |)la(es. A (l('(ini(e distance of the 

 radium from the })lates corresi)onded to a delinile indication of the 

 galvanometer and it was obviously easy to drive the image from the 

 scale by approaching the radium. It Avas remarkable in all these 

 experiments that wlien the preparation of uranium or radium was 



47- 



