III. SURVEYING. 



773 



4. Each time the ball is thrown off (provided there is no other circumstance, 

 such as winding up or regulating the clock, to cause it) is noted on a separate 

 sheet (see the annexed form) with the exact date, the time and hour of the 

 day, and the direction in which the ball was thrown off by naming the re- 

 cess with its corresponding letter in which the ejected ball was found. In 

 places where there are clocks indicating seconds the time must be noted to 

 seconds, otherwise by noticing as accurately as possible the fractions of the 

 minutes. 



5. After each reading the ball is placed again directly on the plate, the 

 clock set in motion, and immediately correctly adjusted, if possible. 



6. In case of greater commotions of the earth, or shocks of an earthquake, 

 which can be recognised as such also without apparatus, a report as to the 

 time and direction must immediately be submitted to the general administra- 

 tion of the telegraph service by the telegraph branch office concerned. 



7. All other movements or disturbances which are being indicated by the 

 instrument are registered, as above, and sent in monthly, or, if nothing have 

 occurred, a report to that effect. 



8. Particular attention must be paid to the daily careful adjustment and 

 regulation of the clocks according to the directions given, in order to render 

 the instruments useful. 



OBSERVATION of an EARTHQUAKE by means of the SEISMOCHROXOGEAPH 

 designed by Von Lasaulx, at the Imperial Telegraph Station at 



2909b. Mallet's original Seismometer. 



R. Mallet, C.E., F.R.S. 



