EARTHQUAKES ON THE PACIFIC COAST 23 



is heavy, while the leverage of the magnet is short and the releas- 

 ing arm long. The magnet was removed from its old position and 

 placed much nearer the point of release; the armature and movable 

 lever were made much lighter, and, when tested, they were found 

 to respond to a much lighter current than in the old form. 



" The governor of the driving clock is of the conical pendulum 

 type, with paddles attached to the arms, which work in a trough 

 filled with oil. In an instrument where the clock is in operation 

 but a small portion of the time this form of regulation is objec- 

 tionable. In our instrument the oil was removed and small strips 

 of rubber attached to the paddles so that they would rub against 

 the bottom of the empty oil trough. This has worked satisfac- 

 torily, as there is no great accuracy required in the rate of this 

 clock. A small double conical pendulum, such as is now used on 

 chronographs by Warner and Swasey or Saegmiiller, adapted to 

 this particular case, would probably be most satisfactory. 



" As the beats of the time-clock are registered on the edge of the 

 plate, it would be much more convenient if the clock beat either 

 seconds or half-seconds instead of about 95 times per minute, as 

 at present. 



" There was too much friction between the spring-pen used to 

 record the clock beats on the plate, owing to inequalities in the 

 glass plates. Less friction and more uniform beats were secured 

 by hinging the pen so that it had a considerable range vertically. 



" The pen for recording the vertical motion has considerable 

 ' creep,' probably owing to changes in the springs due to tem- 

 perature, but this is not a matter of much importance if the instru- 

 ment is always started by the shock. A small lever has been 

 attached to the front of the case of the Duplex Seismograph in 

 such a way that the pen can be raised mechanically and held out 

 of the way while the plate is being changed." 



March 29, 1897. 



Quite a number of reports have been received of late years from 

 the instruments installed in California and Nevada, and these 

 records are of value. It would be of extreme interest if a series of 

 such machines could be distributed around the Santa Clara valley, 

 so as to encircle it on both sides, and so as to be situated on like 

 geological strata. A line of instruments in the valley from Gilroy 



