lOOH] 071 the Carriers of Positive Electricity. 187 



To determine the (/'s by experiment we proceed as follows. Given 

 a charge to the disk, the cylinder being insulated and uncharged, then 

 if V/ and Y.,' are respectively the potentials of the cylinder and disk 

 as determined by tlieir electroscopes, 



fl^{ + ^12 "^l/ = ^' since E^ = 0. 



Thus if a is the ratio of the potential of the cylinder to that of 

 the disk when the cylinder is uncharged, 



Similarly, if p is the ratio of the potential of the disk to that of 

 the cylinder when the disk is uncharged, we have 



Substituting in equation (1) we have 



The quantities a and /? are very easily determined, and from this 

 equation we can deduce the ratio of the charges when we know that 

 of the potentials. By using two electroscopes and determining by 

 means of them tlie ratio of the cliarges received by the cylinder arid 

 disk, we eliminate any irregularities that might arise from variations 

 in the working of the coil used to produce the cathode rays which 

 ionize the gas in the iouizjition chamber. 



If an ion is projected through the tunnel in N along the axis of 

 the tunuel, it will, if there is no magnetic field acting upon it, travel 

 along a straight line and hit the disk. If there is a magnetic field 

 its path, after getting through the hole, will be a circle, since if it is 

 free when once it has got through the hole from any electric force, it 

 will, however, continue to hit the disk until the radius of this circle 

 is less than the radius of the circle passing through the hole, the edge 

 of the disk, and touching at the hole the axis of the tunnel. If d is 

 the distance of the disk below the hole, a the radius of the disk, r the 



radius of this circle is equal to -~ — . When the radius of the path 



i!ia 



of the ion is less than this, the ion will give up its charge to the 

 Faraday cylinder ; when it is greater than this it will give up its 

 charge to the disk. 



If H is the magnetic force acting on the ion, e its charge, m its 

 mass, and r the radius of its circular orbit. 



Her = mv, 



