(571) 
ON THE "LINES" WITHIN EONTOEN INTEEFEEENCE 
PHOTOGEAMS. 
The object of this communication is to show that " lines " or " ghosts " 
which appear within the reflected spectra of Eontgen rays may be due to 
ruptured lattices of crystals. 
It seems probable that some pieces of crystal are chipped out, and some 
partially rotated, during the process of cutting. 
In Fig. 1 AB represents the first ideal plane surface of the cut crystal ; 
P, Q, E, and S projecting columns which were left when the neighbouring 
pieces were chipped out. 
Consider the ray EF. 
Under ideal circumstances it would have given the first reflection at F' in 
the plane AB, but under the assumed condition of the crystal it gives nine 
reflected rays before it reaches F'. A ray parallel to FE and incident at Z' 
will give a reflected ray, whereas it would not have given any reflection if Q 
were removed. On account of these projecting columns the ideal F'E' is 
weakened. 
If Q is rotated slightly towards E, then the rays O, O' will diverge, and 
Y will approach the rays X and X'. The opposite holds true if Q is rotated 
towards P. 
Q thus causes a distribution of the intensity of the reflected rays as well 
as of the transmitted rays. 
By J. Steph. van der Lingen. 
(Eead May 19, 1915.) 
(Plates XXXVII, XXXVIII.) 
e 
Fig. 1. 
