a ,> 9 







:;n 



Figure 34. — An exhibit of gravity apparatus a t the Smithsonian Institution. Suspended 

 on the wall, from left to right, are the invariable pendulums of Mendenhall ('^-second), 

 Peirce (1873-1874), and IVirce (1881-1882); the double pendulum of Edward Kiibel 

 (see fig. 15, p. 319), and the reversible pendulum of Peirce. On the display counter, from 

 left to right, are the vacuum chamber, telescope and flash apparatus for the Mendenhall 

 i-sc, unci apparatus. Shown below these are the four pendulums used with the Menden- 

 hall apparatus, the one on the right having a thermometer attached. At bottom, right, is 

 the Gull apparatus (cover removed) mentioned in the text, shown with one quartz 

 pendulum. 



BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



