Burhanh — A^pjparent Variations of the Vertical. 327 

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of the simj)le pendiilum by placing AB horizontal. Let t be 

 the period of the pendulum so placed. 



The distance CM is the length of the equivalent simple 

 pendulum, namely, one having the same period, T, as the hori- 

 zontal pendulum. 



(1) Sin ^ = "" ^' 



X 



CM 



From the measured value of a; and the observed value of T, 6 

 can be readily computed. 



If the pier or pedestal be tilted in a plane normal to AM 

 through the angle i, the center of mass, M, will move through 



