Velocity of Electrons expelled by X-rays. 751 



o£ the electrons in the four cases. If the scales of abscissse 

 (pressure) be adjusted on the assumption that the maximum 

 distance traversed by an electron is proportional to the fourth 

 power of the atomic weight of the source of the exciting 



O 5 10 15 20 



Pressure., 



Showing that the Ionization-Pressure Curves for Ionization by K and 



by L corpuscular (electronic) radiations are identical. 



Discontinuous line indicates the form of the Sb or 1 curve if the 



velocities had differed by about 10 per cent. 



fluorescent X-radiation, we must reduce the pressures for 

 the Sn, Sb, and I curves in the ratios 1 to '6S, '66, and *52 

 respectively. This places the Sb and I curves slightly to the 

 left of the Ag and Sn curves. — almost in the position of the 

 discontinuous curve of fig. 3. We, however, know that this 

 law gives only an approximation to the truth ; the factors 

 •71, *7S, and '6S were found to give the closest agreement. 

 Such an adjustment of scales has been made in fig. 3, from 

 which we see that within a small possible error the curves 

 are identical. The Ag and Sn curves are, however, curves 



