Victor F. Lenzen and 

 Robert P. Multhauf 



DEVELOPMENT OF 



Paris, France 

 Latitude 49° N 



Cayenne, South America 

 Latitude 5° N 



Figure i. — A study of the figure of the earth was one of the earliest projects of the 

 French Academy of Sciences. In order to test the effect of the earth's rotation on its 

 gravitational force, the Academy in 1672 sent Jean Richer to the equatorial island of 

 Cayenne to compare the rale of a clock which was known to have kept accurate time in 

 Paris. Richer found that the clock lost 2 minutes and 28 seconds at Cayenne, indicating 

 a substantial decrease in the force of gravity on the pendulum. Subsequent pendulum 

 experiments revealed that the period of a pendulum varied not only with the latitude but 

 also regionally, under the inlluence ol topographical features such as mountains. It 

 became clear that the measurement of gravity should be made a part of the work of the 

 geodetic surveyor. 



