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L. A. COTTON. 



Explanation of Figures and Plate LXII. 



Figure 1.— Pendulum No. 1 (Heidelberg Pendulum). 

 The deflections of the vertical registered by both booms 

 are represented by the changes in the ordinates of the 





curves, which are drawn to a scale on which one centimetre 

 represents about 1*48 seconds of arc. The amount of 



