326 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
a wind. A few miles eastward, however, in the river-laid valley deposits, the shock 
was felt by very few persons. 
In the town of Gardnerville, some few miles east of Genoa, a number of people com- 
plained of a feeling of nausea while eating breakfast at the time of the earthquake, but 
felt no motion. In all cases the shock felt was characterized by long, gentle motion ; 
in no cases was sharp movement experienced. 
At Virginia City, about.6 miles east of the Rocky Hill mine, the shock was felt by very 
few people, and they were in the tops of the higher buildings. Around Dayton and 
nearby towns no reports came of persons feeling the earthquake. The Virginia Range 
seems not to have been greatly shaken. At Carson, the most reliable and abundant data 
were obtained. Mr. C. W. Friend, the well-known meteorological observer, obtained a 
seismograph record of the shock,’ which was by far the heaviest ever recorded by him, 
the stylus of the instrument swinging entirely off the plate. Yet the motion was so 
gentle and of such along period that sleepers were not generally awakened. The time 
of oscillation was not determined, but was described as being like the swinging of a ham- 
mock. The seismograph record is peculiar in that the stylus appears nearly to have 
retraced its course over one large curve. Carson lies about 3 miles east of the steep 
rise of the Sierra Nevada, with a deep deposit of river wash between. At the south- 
west, however, a low hill of schistose rocks just enters the town limits. This structure 
may play a considerable part in the peculiar motion of the earth here in this and other 
earthquakes. 
At Paradise Valley, north of Winnemucca, the earthquake was felt by the few people 
awake or moving at that early hour. A rancher who happened to be near a small pond 
noticed an unusual agitation of the water, and supposed an earthquake to be the cause. 
The time was subsequently found to correspond with that of the shock, as reported 
elsewhere. No motion was felt, however. 
. 
EXPERIMENTS WITH A SHAKING MACHINE. 
By F. J. Roasrs. 
The investigation described below was undertaken with the hope of offering some 
explanation, based directly on experiment, of the greater destructiveness of earthquakes 
in regions where the foundations of structures are supported by more or less soft ground 
than where these foundations are based on solid rock. 
As an earthquake consists in the actual shaking of the earth’s crust it would seem, 
upon first thought, that the more rigid the foundation the more destructive would be 
the effects of the earthquake upon the structures so supported. This is in general not 
true, however. 
In conversation with Dr. Branner, the great desirability of some experiments on this 
subject was suggested to the writer. In the first experiment which promised any inter- 
esting results a bucket of molding sand was poured out upon a board about 20 x 30 
inches. The board was shaken in a horizontal direction through an amplitude of 2 or 
3 centimeters, by means of a small motor. When the sand was moderately wet, the 
amplitude of vibration of the top of the mound was greater than the amplitude of vibra- 
tion of the board on which the sand rested. This result is contrary to what I should 
have expected. When the result of this preliminary experiment was reported to Dr. 
Branner some time afterwards, he was greatly interested and urged the writer to carry 
on a series of similar experiments on a larger scale, the same to form a part of the report 
of the Karthquake Investigation Commission. As a result the apparatus described 

.’ This seismogram is referred to in another part of the report. 
