PRESSURE ON RESISTANCE OF METALS. 



591 



For the temperature coefficient between 0° and 100° there are the 

 values .00398 by Dewar and Fleming,^^ and .00458 by Matthiesen and 

 Vogt.-^^ These are both considerably lower than .00517, the value 

 found above. 



The general character of the results is the same as for indium and tin. 

 When the resistance-pressure curves are plotted to the same initial 

 scale, the curves for higher temperatures are steeper and have the 

 greater curvature. 



Cadmium. This material was from Kahlbaum, grade "K." It was 

 made into wire by extruding when hot into a wire 0.06 inch diameter. 

 The surface was then deeply etched to remove any possible impurity 

 of iron introduced by the extrusion. From 0.06 inch it was drawn to 

 the final size, 0.005 inch, through diamond dies and wound with one 

 layer of silk insulation. The drawing and winding were done by the 

 New England Electrical Works, Lisbon, N. H. It was seasoned after 

 winding into the coreless toroid for pressure measurements by keeping 



TABLE IV. 

 Cadmium. 



at 130° and 0° alternately for 30 minutes over a space of 8 hours and 

 by 4 applications of 12000 kg. at 100°. Connection was made by 

 soldering with "fine" solder. The resistance at 0° was 33.5 ohms. 

 The smoothed results are shown in Table IV and the experimental 



11 J. Dewar and J. A. Fleming, Phil. Mag. 36, 271-299 (1893). 



12 A. Matthiesen and C. Vogt, Phil. Mag. 26, 242 (1863). 



