58 THE NEW KNOWLEDGE. 



the arc of this very circle. The size of the circle is indicated 

 in the diagram, and the length of its radius is fixed by the 

 relative positions of E and G. 



Now, the magnetic force that is just sufficient to cause 

 the deflection of the particles to C is easily measured; and 

 hence, we have the following equation: 



Radius of circle (which we know)= 



eX g 



which with a shifting of one quantity to the other side of 

 the equation, is : 



mv 



Radius of circle (known) X magnetic force (known) = 



And we are thus, to some extent forwarder, at least; for we 

 have a definite value for, 



the mass of the corpuscle X its velocity 

 its electrical charge 



Is there any hope of our going further? There is. We 

 must now determine the velocity of the corpuscles. 



