132 EAKTHQUAKES ON THE PACIFIC COAST 



about the same intensity. Several loops extend about 20 milli- 

 meters from the center. 



The shock lasted from five to twelve seconds, according to some 

 persons, while others considered that the earth shook for fully 

 a minute; motion great but gentle; two persons felt nausea; four 

 regulators in jewelers' shops, on walls running west-northwest 

 and east-southeast, stopped at about 3.10, two of them indicat- 

 ing 3.10.30 and 3.10.35 respectively. A clock with heavy mer- 

 curial pendulum on same wall was not stopped. — F. G. Blinn. 

 Intensity = (VI). — William Ireland. 



Three miles from Collinsville, in the region of greatest disturbance, 

 houses rocked and pieces of plaster fell (VII); articles shaken 

 from mantelpieces, etc.; chickens shaken from their perches; 

 dogs barked; two chimneys demolished (VIII), and one had the 

 upper part twisted 45 degrees; goods thrown from shelves in 

 stores. — F. E. Booth, manager of Black Diamond Canning Com- 

 pany, in a letter to F. G. Blinn. 



Mills College: in the seismograph record at this place there are 

 great loops SO millimeters long, which appear to have been pro- 

 duced by the swinging of the pendulum after the shock. It is 

 necessary to give the seismograph pendulums some stability, but 

 they are adjusted to swing in a long period, much longer than 

 that of the ordinary earthquake shock. It is evident, however, 

 that in an earthquake like this the vibrations might be nearly 

 synchronous with those of the pendulum, which would thus be 

 thrown into violent oscillations. In most earthquakes this is 

 not likely to happen. Possibly the long loops in some of the 

 other seismograph records may be due to the same cause. 



San Francisco: No damage was done in the city. The newspaper 

 accounts seem to be exaggerated. Motion from west-northM^est 

 to east-southeast. — J. B. Trembley. 

 Time of shock in San Francisco, 3.10.42. — Prof. Davidson. 



Fort Point Light-Station: the shock was preceded and accompanied 

 by a rumbling noise and lasted eight or nine seconds. The 

 keeper felt three shocks, the first short and light, and about 

 fifteen seconds later one more distinct; a minute afterwards, the 

 last, which was a tremor. Doors were opened; windows and crock- 

 er,y rattled and people were aroused from sleep (VI?) 



Lime Point Fog-Signal Station: time 3.10.32. Lasted about five 

 seconds, and was accompanied with a noise like the rumbling of 

 distant thunder. 



Forest Hill: in the Mayflower mine no sign of an earthquake at 

 600 or 800 feet underground. Directly over the mine the shock 

 was strong enough to rattle a wash-bowl against a pitcher. — 

 S. E. Eeamer, San Francisco. 



