Seismic Radiations. 
25 
1909-10.] 
reflected waves, one of distortion and one of condensation, so long as the 
angle of incidence is not greater than a certain value determined by the 
relation betwen the speeds of propagation of the two rays. For angles of 
incidence greater than this critical value there will be no reflected con- 
densational wave. 
In this paper I confine myself to further consideration of the case in 
which the elastic solid is backed with air. The case in which water takes 
the place of air will present similar features. The distribution of the 
energy among the various types of reflected and refracted rays is shown 
diagrammatically in the published abstract of an address I gave in 1899 
before the Royal Society of Edinburgh (see Proc. Roy. Soc. Edin., vol. xxii.). 
These diagrams have also been reproduced in my book on the Physics 
of Earthquake Phenomena, p. 182. They show certain of the outstand- 
ing phenomena in a way which is more easily understood than the 
mode in which they were first represented in the original papers already 
referred to. 
The following tables are taken from the paper in the Philosophical 
Magazine (vol. xlviii. p. 87), and show how the energy of the incident ray 
is distributed among the reflected and refracted rays into which it is 
divided. 
Here A, A v A' give the energies associated with the incident, reflected, 
and refracted rays of condensational type, 0, 6, 6' being the corresponding 
angles of incidence, reflexion, and refraction ; and B, B v B', with <f> 
and <p', refer similarly to the rays of distortional type. In the first table 
the incident ray is condensational ; in the second the incident ray is 
distortional. 
In making these calculations, I assumed the density of rock to be 3, 
the rigidity to be 1*5 X 10 11 , the incompressibility to be 2 ’5 x 10 11 , the density 
of air to be 0*0015, and its incompressibility to be 1*5 X 10 6 . 
1. Condensational Wave Incident in the Rock. 
«■ 
A . 
A a . 
e'. 
A '. 
0 . 
B. 
0 
1 
0-9999 
0-00013 
14 ° 2 ' 
1 
0-828 
0°-9 
0-00013 
8 ° 
0-172 
26 34 
1 
0-464 
1 -7 
0-00011 
15 
0-536 
45 
1 
0079 
2 -7 
0-00009 
24 
0-921 
59 2 
1 
0-0002 
3 -3 
0-00007 
30 
0-9999 
73 18 
1 
0-003 
3 -7 
0-00006 
34 
0-997 
84 17 
1 
0-091 
3 -8 
0-00005 
35 
0-909 
