GENERAL MEETING. 37 
289TH MEETING. OcToBER 9, 1886. 
The President in the Chair. 
Seventy-eight members and guests present. 
The Chair announced the election to membership of Messrs. 
Coorer CurticE, Henry MitrcHeLtt, Henry Gustav Bryer, 
and Newton LEMUEL Bares. 
The subject for the evening was 
THE CHARLESTON EARTHQUAKE, 
which was discussed by Messrs. T. C. MenpENHALL and W J Mc- 
GEE and Prof. CHarLEes G. Rockwoop of Princeton, N. J. 
Mr. MENDENHALL spoke of the odor observed on Sullivan’s 
Island previous to the shock, of the time of the clock-stopping 
shock in Charleston, of the detonations accompanying the various 
shocks and heard in Charleston, Summerville, and elsewhere, of the 
torsional movements of monuments, and of the directions in which 
various structures were thrown down. He exhibited an isoseismal 
map compiled from data gathered by the U.S. Signal Service. He 
also stated at second hand a novel theory for the origin of the earth- 
quake, and spoke of the convergence of opinion of geologists and 
physicists in regard to the condition of the interior of the earth. 
He accepted as the time of the clock-stopping shock in Charleston 
9h. 51’ 20” Pp. M. 
Mr. McGee described the geological relations of Charleston, 
showing that a depth of 2,000 feet of clastic rocks had been demon- 
strated beneath the city, and that the total depth to the crystalline 
rocks might be as much as one mile. He described the pheno- 
mena of deformation of rails and other railway structures, gave in 
detail an observation of a severe shock at Summerville, described the 
detonations, and exhibited numerous photographs illustrating the 
destructive work of the earthquake and the formation of craterlets 
and sinks. 
Prof. Rockwoop exhibited an isoseismal map compiled from data 
gathered by the Earthquake Commission, and characterized by far 
greater irregularities in the form of contours than were shown by 
Mr. Mendenhall’s map. He called attention to the fact that nearly 
all the isoseismal curves show salient angles toward the northwest. 
He dwelt upon the exceptional nature of this opportunity for earth- 
quake investigation, and urged that the utmost advantage be taken 
