THE INFLUENCE OF DISTURBING ACCELERATIONS 



129 



oscillates at natural and induced frequencies. In this case the induced 

 oscillations of the Cardan suspension are mainly due to the horizontal 

 acceleration component of the vessel's motion. 



Let us introduce a mobile system of co-ordinates IC related to tlie instru- 

 ment. In the absence of vertical accelerations the pendulum of the 

 gravimeter is orientated parallel to the axis 0^. Let us select a further system 

 of co-ordinates xOz in which the direction of the axes is orientated relative 

 to the fixed horizon. 



Fiu. 2. 



The transition from one system to the other can be easily achieved by the 

 following scheme 



X = .Xq + % 



X = XQ + i cos 9? + C^'m 

 z = ^0 — I sin 9? + C cos 



(17) 



The system |04" moves relative to xOz and rotates. 



The variables in formula (17) are Xq, Zq and cp. 



$", C" denote projections of the acceleration of the system of co-ordinates 

 |0C translated to the axes C and | via ^qCq^ the co-ordinates of the centre 

 of gravity of the pendulum. 



It is common knowledge in mechanics that the proiection of the acceleration 



Applied geophysics 9 



