454 



Mr Groiuthe7\ On the Transmission of 0-rays. 



thicknesses still the carve has another point of inflection; the 

 absorption becomes less rapid, and the curve appears to become 

 asymptotic to the axis of x. The small amount of rays trans- 

 mitted by these thick sheets did not allow of any very exact 

 determination of the shape of this part of the curve. The ex- 

 periments seemed to indicate, however, that it did not depart 

 widely from an exponential form. 



It will be seen that the curve thus obtained agrees well in 

 its main outlines with the form of absorption curve predicted by 

 Prof. Thomson's theory. It shows the same initial flat portion, 

 the steeper middle portion and the final gradual tailing away. 



1-00 



•80 



■(oO 



■Uo 



•20 



•005 cms. 



Fig. 6. 



More than a general resemblance could not well be expected. 

 Prof Thomson's theory applies rigidly only to thin sheets of ab- 

 sorbing media. Again the factor k in the equation 



is a function of the energy of the rays, and decreases as the energy 

 is diminished. As the energy of the rays is continually diminish- 

 ing during their passage through the aluminium, the value of k 

 must also diminish with the thickness, and thus cause a de- 

 parture from the predicted form. The last column of Table II 



