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TTNIVERSITY OF VIRGINIA PUBLICATIONS 



ience in detail and hardly deserve attention in themselves. However, a 

 description of the apparatus in use here at the present time may assist 

 some teacher in the task of construction. If so, then this note is justified. 

 To begin with the modifications introduced since 1907 are briefly: 

 (a) mounting of the apparatus close to the wall, taking advantage of the 

 increased stability offered. This, for instance, permits the lecturer to 

 walk about during the course of the experiment, (b) Further protection 

 against disturbances by surrounding the bob with a box to shield its large 

 surface from air-currents, (c) Employment of a bob filled with mercury 



Fig. 6 



to damp out the tremors incident to starting the pendulum, (d) Use of 

 a tripod for the recording lever (see below). 



Figure 7, reproduced from a photograph, shows the apparatus complete 

 excepting the lantern, screen and point of suspension. The pendulum is 

 suspended after the manner described by Professor Smith using steel 

 piano wires of size no. 24 B & S and 550 cm. long. The amplitude of swing 

 is about 5 cm. (from centre). The bob is made of one of those cast iron 

 shells such as are furnished by apparatus dealers for the experiment of 

 bursting b}^ freezing water. Filled with mercury it weighs 6 kgm. The 



