THE INFLUENCE OF DISTURBTNG ACCELERATIONS 127 



Experience shows that to measure Ag with sufficient accuracy it must be 

 less than 0.01. Proceeding from this, formula (13) can be rewritten ^vith 

 an accuracy of up to 10~® thus : 



(14) 



sep 

 Being in possession of the recorded motion of the gravimeter pendulum 



when deflected from a state of eqiiilibrium, we can find the value B = e - , 



o 



from which — —^ = In B. 



The dynamic coefficient can be determined in this manner from the formida 



?^=-^lnB, (15) 



if we kno\v Tf^, the period of the vessel's oscillation and are also in possession 

 of the recorded movement of the gravimeter pendulum when deflected from 

 a state of equilibrium. 



We are now therefore in a position to find the amplitude of the vertical 

 accelerations as we know the dynamic coefficient X and have measured the 

 mean oscillatory amplitude of the pendulum. 



If it is possible to read off the value Aq, i.e. if the observations close with 

 the pendulum completely at rest, we can obtain from formulas (7) and (14) 

 a formvda for calculating the dynamic coefficient of the gravimeter for two 

 readings, A^ and A2, on the gravimeter scale at points of time ^^ and t^ and 

 for the known position of static equilibrium Aq. 



X = ^ -A^I^ = 0.3663 log ^f^ -^ . (16) 



Alt fo — 1\ -^2 ^02 1 



The values Aq, A^, A^ can be read ofi" from the curve of change in the 

 reading shown in Fig. 1. 



For example, let the deviation of the system from a position of equilibrium 

 decrease by 10 times in relation to the initial deviation in a period of 

 10 minutes, i.e. 



^2~^0 



10. 



Let J"^ = 10 sec. Then, by substituting in formula (16) we obtain 



10.60 



