[ 223 ] 



XXI. The Application of the Ultra-Micrometer to the Mea- 

 surement of Small Increments of Temperature. By W. 

 Sucksmith, B.Sc, University of Leeds*. 



IN Whiddington's ultra- micrometer apparatus t two oscil- 

 lating valve circuits were set up. In the valve-anode 

 circuit of the second was inserted a three-stage amplifier, 

 together with a loud-speaking telephone, to magnify suitably 

 the heterodyne note produced. The condenser in the first 

 oscillating circuit consisted of two parallel plates, the 

 variations in the distance of which produced variations, in 

 the note emitted from the telephone. A tuning-fork was 

 set up close to a small telephone, in order to provide a 

 standard of pitch to which the note from the interfering 

 circuits could be adjusted. The oscillations of this fork are 

 amplified into the loud-speaking telephone mentioned above. 

 This differed from the original experiment in that pre- 

 viously a third oscillating valve circuit had been set up 

 inducing into an amplifier, with capacity and "inductances so 

 large as to produce an audible note in the telephone. 



Fig-. 1. 



The method used was to attach a met?«l bar to one of the 

 condenser plates, and measure change in the temperature 

 by the change in the note produced in the telephone. 



Fig. 1 shows a geometrical slide carrying two rigid vertical 



Communicated by Prof. R. Whiddiugton, M.A., D.Sc . 



t Whiddino-ton. 

 pp. 634-9 



The Ultra-Micrometer," Phil. Mag. ser. 6. vol. xl. 



