496 Prof. McLennan and Mr. Found on Delta Radiation 



of 40 volts was reached, none escaped from P at all, and 

 the current became constant and consisted o£ the first four 

 constituents mentioned above. This result was exactly in 

 accordance with what Logeman had previously observed, 

 and it showed that the apparatus was working satisfactorily. 



Experiment II. — In the second experiment the polonium- 

 coated disk, P, was kept joined to the positive terminal of 

 the battery at a steady potential of 80 volts. This ensured 

 that no electrons escaped from P. 



The electromagnet was then excited with currents of 

 different intensities, and readings were taken on the corre- 

 sponding currents through the chamber to the zinc plate X. 

 The results in one of the experiments of this type are given 

 in Table II. and are represented graphically in PL VII. fig. 3. 



From these it will be seen that the current gradually fell 

 off as the field was increased and ultimately reached a steady 

 state with a field of approximately 1000 gauss. 



Table II. 



Voltage on polonium plate =80 volts, posi 



five. 



Current through 

 the coils of the 

 electromagnet. 



Value of the 

 magnetic field. 



Electrometer 

 deflexion per min. 



Current XlO 5 

 e.s.u. 



amps. 



gauss. 



mm. 





zero 



zero 



23-0 



84 



•5 



240 



22-3 



72 



1-0 



410 



18-0 



58-3 



1-7 



690 



15-0 



49 



2-5 



905 



140 



45 



30 



1020 



132 



43 



33 



1100 



135 



44 



3-7 



1]90 



11-5 



37 



4-4 



1275 



140 



45 



4-7 



1300 



12-7 



41 



5-0 



1330 



137 



44 



6-0 



1400 



13-7 



44 



From the known properties of the ionization currents of 

 the alpha rays and of recoil atoms it is clear that a field 

 of this intensity was not sufficient to modify to any 

 appreciable extent the current carried by them to X, and it 

 follows therefore that the decrease in the current observed 

 was due to the action of the magnetic field in curling the 

 electrons emitted by the zinc plate under bombardment by 



