44 REPORTS ON THE STATE OF SCIENCE.—1914. 
Birmingham, Mr. L. F. Richardson of Eskdalemuir, and Mr. J. E. 
Crombie of Aberdeen. 
Il.—Seismic Activity in 1911. 
The visit of the British Association to Australia makes it necessary 
to have the greater part of this Report in proof at an earlier date than 
usual. The list of origins for 1911, in continuation of those given in 
previous Reports, is not completed at this date; but it is hoped to add 
it at the end of the Report before it is finally printed off for 
distribution. 
IlI.—Distribution of Earthquake Centres. 
Study of the information collected by Milne in previous Reports has 
suggested a new form of the map which he has usually printed 
showing the distribution of large earthquakes. On some of these 
maps he has shown Libbey’s Circle, and on others a cycle of his 
own running through the chief earthquake centres, 
On scrutiny of the distribution of centres not thus accounted for, 
the existence of a curve of secondary disturbance was suggested, 
with the suggestive feature of enclosing most of the land on the earth’s 
surface—skirting especially the Western coast of North America and 
the Eastern coast of Asia. Adjustments by trial and error of these 
two curves showed that it was not difficult to make them great circles 
cutting at right angles; but not easy to make them account for all 
the striking facts. More or less by accident, the third great circle 
cutting both at right angles was drawn, and immediately several 
striking geographical features fell into line. Further work on this 
system of three great circles suggested after many trials a system 
symmetrical with respect to the earth’s axis, the points of intersection 
being at about 55° (accurately tan ~!./2) from the poles; and there 
was little trouble in fixing the approximate longitudes at 259 + 60° n 
Kast. 
A system of three great circles cutting at right angles divides the 
surface of the sphere into eight equilateral right-angled triangies. If 
we project each of these on a tangent plane at its centre, we get 
an octahedron surrounding the sphere, and we can unwrap it into a 
plane in various ways. The particular plan of the accompanying map 
is adopted in order to bring out the striking symmetry, both seismo- 
logical and geographical, of the earth as thus represented, a symmetry 
only slightly disguised by the one-sidedness of the water covering. 
[ We can imagine the distribution made quite symmetrical, and then 
the upper right-hand corner dipped slightly more under the water; but 
we will neglect this point for a moment. ] 
Six of the triangles are easily recognised, the other two have 
been divided by their median lines in order to show the symmetry 
while keeping the figure compact; but ABC and CBD could be detached 
from AC and CD, and joined along CB placed in a vertical position, 
thus keeping the symmetry at the expense of a little detachment. 
Let us consider the triangle EFK, which is chiefly Asia. India lies 
nearly on the median line, pointing to the apex of the triangle; and just 
