which two or four pendulums were bung at the same 

 time. Finally, early in the present century, Vening 

 Meinesz found that the Faye-Peirce method of swing- 

 ing pendulums hung on .1 Stuckrath four-pendulum 

 stand solved the problem of instability due to tin- 

 mobility of the soil in Holland. 



I In- 20th century has witnessed increasing activity 

 in the determination of absolute and relative values of 

 gravity. Gravimeters have been perfected and have 

 been widely used for rapid relative determinations, 

 but the compound pendulums remain as indispensable 

 instruments. Mendenhall's replacement of knives by 



■ > : 1 ut. : 1 ililc pendulums has been 



used also for reversible ones. The Geodetic Institute at 



Potsdam is presently applying the Faye-Peirce method 

 to the reversible pendulum. 11. Pendulums have been 

 constructed of new materials. Mich as invar, fused 

 silica, and fused quartz. Minimum pendulums for 

 prei ise relative determinations have been constructed 

 and used. Reversible pendulums have been made with 

 "I" cross sections foi bettei stiffness. With all these 

 modifications, however, the foundations ol the pi 

 designs of compound pendulum apparatus were 

 created in the 19th century. 



"'■ K. Rj 11:111 si in :■ Method ol ' 1 



Potsdam In Means of the Reversible Pendulum," Bulletin 

 Geodesique M m I, 1. [959 I, QO >1, p. 72. 



For sale by the Superintendent of Documents, L'.S Government Printing Office 

 Washington, D.C., 20402 lair.- 70 rents. 



