1908] 



on 



the Carriers of Positive Electricity. 



189 



Current through Electromagnet 

 in Amperes. 

 0-5 

 1 



2-5 

 2 

 2-5 



H. 



1330 

 2570 

 4000 

 4900 

 5600 

 6000 

 6400 

 6660 



When, as in our Faraday cylinder, d = b mm. e = 2 mm., the radius 



of the critical circle 



2a 



0*725 mm., we see by the appHcation 



of equation (2) that if e/m = 10'*, the potential-difference Y required 

 to reduce the radius of the orbit to the critical value would, when 

 the currents through the electro-magnets were 1, 2, 3, 4 amperes, be 

 respectively 170, 620, 900, 1100 volts. These are the potential- 

 differences between the gauze and the top of the cylinder N required 

 to send the ions to the plate. The following table gives the charge 

 acquired by the disk when the sum of the charges on the disk and 

 Faraday cylinder was 100 for different strengths of magnetic fields ; 

 assuming that all the ions carry the same charge, these numbers 

 represent the percentage of the ions passing through the hole which 

 reach the disk. In the table V is the potential-difference between 

 the gauze and N in volts, t the current through the electro-magnet 

 in amperes, and n the percentage of ions which reach the disk. The 

 gas in the tube was hydrogen. 



On looking at the numbers we see that until the voltage exceeds 

 160 volts there is no appreciable difference between the number of 

 ions going to the disk when the magnetic field is due to a current 

 of 1 ampere, and when it is due to 2 amperes. We saw, from the 

 preceding calculation, that a voltage of 170 volts would carry ions 

 for which ejm = 10^ to the disk against the electric current, while 



