318 Prof . W. L. Bragg- and Messrs. James and Bosanquet : 



A simple calculation shows what the width o£ the slit of 

 the ionization-chamber must be in order that all the homo- 

 geneous rays may enter it. It is advisable to limit this as 

 much as possible, as the amount o£ general radiation is 

 directly proportional to its width. The breadth of the 

 homogeneous beam may be found by a survey with a very 

 fine chamber-slit set at a series of angles. For the higher 

 orders, the chamber-slit must be wider in order to include 

 the two components of the K a doublet. 



10. The comparisons which have been made are tabulated 

 below, and the results are plotted in the form of a graph 

 in fig. 2. 



ane. 



Intensity. 



Vlntensity. 



Cosec 0. 



T* 1 ^ 



/Ew x 



100 



100 



10 



9-21 



612 



24-80 



200 



19-90 



4-46 



4-60 



122 



11-05 



300 



4-87 



2-21 



3-07 



29-8 



5-49 



400 



0-79 



0-89 



2-30 



4-85 



2-20 



500 



0-116 



0-34 



1-84 



0-71 



0-84 



110 



50-4 



7-10 



6-50 



310 



1760 



220 



610 



2-47 



3-25 



37-3 



6-12 



330 



071 



0-84 



2-17 



4-35 



2-08 



111 



9-00 



3-00 



10-62 



55-1 



7-45 



222 



33-1 



5-75 



5-31 



202 



14-25 



333 



0-58 



0-76 



3*54 



3-55 



1-89 



444 



2-82 



1-68 



2-65 



17-2 



4-16 



555 



0-137 



0-37 



2-12 



0-84 



0-92 



311 



1-17 



1-09 



5-56 



722 



2-70 



622 



2-69 



1-64 



2-78 



16-40 



4-06 



331 



0-81 



0-90 



4-23 



4-95 



2-23 



511 



0-61 



0-78 



3*54 



3-74 



1-93 



711 



0-302 



0-55 



2-58 



1-87 



1-37 



The figures in the column headed " Intensity " were 

 initially expressed in terms of the (100) reflexion, which 

 was put equal to 100. Since it was discovered later that 

 the (200) reflexion was a more reliable standard of intensity, 

 all the other intensities have been determined relatively to it. 

 In order to facilitate comparison with figures given by other 

 authors, its value has been fixed at 19*90, since the ratio 

 100:19*90 was the most reliable value for the ratio 



