42 PHILOSOPHICAL SOCIETY OF WASHINGTON. 
studies, discussed the relation of destructiveness to amplitude of 
vibration and to rate of acceleration, and requested Mr. McGee to 
describe more specifically than at the last meeting the phenomena 
observed by him in connection with a severe shock in Summerville. 
Mr. McGee said that during the tremor the bedstead upon which 
he lay left the floor from fifteen to thirty times, the departures 
being roughly estimated at three per second. The clear ascent, as 
judged from the force of the return blow, ranged from one-fourth 
inch to two or three inches. The bed stood on the ground floor 
of a wooden house, supported on piers. Earlier shocks had crushed 
or driven down the piers under the heavier parts of the house, so 
that the weight was borne in large part by piers under verandas, etc. 
Mr. Paut said that if the floor in descending separated from the | 
legs of the bedstead its acceleration of motion must exceed that due 
to gravitation. The fall of the earth manifestly could not be faster 
than that of the bedstead. Assuming the accuracy of the observa- 
tion the only possible explanation would seem to be that the floor 
had behaved as an elastic spring. 
Dr. How.anp described a shock observed by himself, and said 
that of some hundreds of chimneys observed by him in Charleston 
75 per cent. had fallen to the west. 
The PrestpEnt spoke of the bearing of the earthquake upon sani- 
tary matters. The water mains. in Charleston had been run in 
some places through sewers, and there is no assurance that these 
mains are now in such condition as to render contamination im- 
possible. 
Mr. Durron inferred from the magnitude of the area through 
which the shock was felt, as compared with its moderate destruc- 
tiveness in the central region, that the centrum lay at great depth. 
Mr. Breit was much interested in the statement that, even at 
considerable distances from the centre of disturbance, the noise ac- 
companying the earthquake either preceded the shock or was per- 
ceived simultaneously with it. This, he thought, indicated that the 
sound was of local origin. The great velocity with which the 
earthquake disturbance had been propagated seemed to him to pre- 
clude the idea of a sound-wave from the centre of disturbance as 
the cause of the noise perceived. Any sound due to this cause 
should, he thought, at considerable distances, have been observed 
after the experience of the shock. 
He also spoke of the worthlessness of testimony regarding the 
