296 On X-Rays and Scattered X-Rays. 
Corrected Corrected Ratio of 
' Radiator. Time. deflexion deflexion deflexions o 
of A r of A.,. X x and A 2 . 
Ratio 
of 
! intensities. 
1 
1 
•95 
1 
1 
1 
1-04 
1 
i— i 
1 
102 
I 
1 
Cu GO sees. 33 -.32 60-67 54-9 : 100 
Sn 180,, 6-27 12-15 524 : 100 
Cu 50 .. 23-6 38-8 60"8 : 100 
Sn 180,, 665 10-5 633:100 
Cu 40 „ 275 42-45 65:100 
Sn 240 „ 13-6 20 5 663:100 
From these experiments there was no indication o£ a 
decided variation ; we conclude that there was equality of 
intensity in the two directions. Another group of substances 
classified according to their behaviour under X-ray trans- 
mission includes W, Pr, Pb, and Bi. These emit a radiation 
which appears to differ from that from any of the other 
groups referred to. When the radiation from lead was tested 
in a similar way, no evidence of scattering was obtained. 
Experiments were also made to determine the behaviour 
of a number of these elements under more penetrating rays, 
but the conditions of experiments have not yet been varied 
sufficiently to lead to definite conclusions. 
These results thus afford strong confirmation of the 
electromagnetic pulse theory of X-rays, and of the theories 
of scattering and of polarization based on this. 
The method of comparing the intensities of radiation in 
the two directions indicated is a delicate one for detecting 
the presence of scattered rays, or of measuring the control 
over radiating electrons, exercised by the primary pulses while 
producing or stimulating the production of secondary rays. 
The scattering of " soft " X-rays by substances of low 
atomic weight has been shown to be almost perfect, and the 
appearance of a radiation which is very far from a purely 
scattered radiation, when more penetrating rays are used, has 
been shown in a very marked way. The small proportion 
of scattered rays in other secondary radiations has been 
demonstrated. 
These experiments, however, do not show that under 
suitable conditions scattered rays may not be obtained from 
elements hitherto found to emit only an uncontrolled secondary 
radiation. 
I wish to thank Mr. F. J. Thorpe, B.Sc, for assistance in 
conducting some of these experiments. 
George Holt Physics Laboratory, 
Liverpool. 
