PENDULUM METHODS 



163 



FlG.2 



Fie. 3 



Fie.4 



F/G.l 



Fi6.6 Fis.7 Fie.8 



Correct P/umb Faul+y but Faulty and 



Markings Usable Workings Useless Markings 



Fie. 3 



Plate XI. — Thurmann's deviation apparatus. 



