38 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
\ 
of it. He spoke also of the complexity of earthquake movements, 
and the difficulties to be overcome in analysing them. He thought 
that the conspicious inequality in the violence of the shocks at lo- 
calities not widely separated was to be ascribed to the intersection 
and combination of rock waves deflected by reflection and refrac- 
tion. Two intersecting waves would be especially destructive at 
their nodal points, and comparatively harmless at their points of 
interference. 
It was announced by the President that the discussion would be 
continued at the next meeting. 
290TH MEETING. | OcToBER 23, 1886. 
The President in the Chair. 
Sixty-seven members and guests present. 
The discussion of 
THE CHARLESTON EARTHQUAKE 
was resumed, the principal speakers being Mr. Everrerr HayDEN 
and Mr. H. M. Paut. Remarks were made by Messrs. McGeEg, 
Bruuines, Rosinson, Durron, BELL, CLARKE, and GILBERT, and 
by Dr. E. P. Howxanp, who was present by invitation. 
Mr. Haypen first discussed a chart on which were plotted the 
areas disturbed by earthquakes in the southeastern United States 
from 1874 to 1885, compiled from Rockwood’s Notes in the Ameri- 
can Journal of Science. This indicated two earthquake belts, one 
along the Appalachians, the other along the coast. In the former 
28 shocks are recorded, in only 3 of which the area is as great as 
1,000 square miles (2 in central Virginia, and 1 in western North 
Carolina and northern Georgia); in the latter 5 are recorded, 
only 1 of which (that of 1879 in Florida and Georgia) was at all 
severe. So far as this evidence goes, therefore, we should have ex- 
pected a severe shock like that of August 31st to have originated 
in the Appalachians and to have been orogenic in character, an 
accompaniment of the gradual elevation of the range. 
He then proceeded to give a summary of the information which 
had reached the Geological Survey up to date, illustrating by charts 
of isoseismal and coseismal lines. The geologic and physical phe- 
nomena in the region of greatest intensity having been already dis- 
