134 BRIDGMAN. 



gation did not fall within the present program, and the results are 

 given as found. 



At 0° the relation between pressure and resistance is linear within 

 the limits of error. The maximum departure of any point from the 

 linear relation was 0.3% of the total pressure effect, and the departures 

 from linearity were distributed at random. The average pressure 

 coefficient of resistance between and 12000 kg. was — 0.064272. 



At 52.24° the relation between pressure and resistance was again 

 linear within the limits of error, but there was sensible hysteresis. 

 The maximum width of the hysteresis loop was 1% of the total effect. 

 The ascending and descending points all lay smoothly on their respec- 

 tive branches of the hysteresis loop without departures of more than 

 0.06% of the effect. The average pressure coefficient between and 

 12000 kg. was - 0.064194, less than the value at 0°. 



At 95.88° the relation between pressure and resistance was sensibly 

 not linear, but could be represented within the limits of error by a 

 second degree curve. The maximum departure of any observed point 

 from the second degree curve was 0.35% of the maximum effect. The 

 departure from linearity is in the abnormal direction, that is, the 

 average coefficient between and 6000 is less numerically than the 

 average coefficient between and 12000 kg. The average coefficient 

 to 12000 was - 0.064488, and that between and 6000 was 

 — 0.064372. It is to be noticed that somewhere between 0° and 100° 

 the pressure coefficient of resistance has passed through a minimum. 



The temperature coefficient of resistance at atmospheric pressure is 

 normal in being positive, but the direction of curvature is abnormal. 

 The average coefficient between 0° and 52° is 0.001076, and between 

 0° and 96° 0.001030. 



"Comet" Alloy. This is an alloy of the following composition: 



It is made by the Electrical Alloy Co. and was furnished by them in 

 the form of wire 0.005 inches in diameter, and doubly covered with 

 silk insulation. It was wound for the measurements into a coreless 

 toroid of 283 ohms resistance at 0°. Readings were made on the 

 Carey Foster bridge in the usual way at 0°, 51.22°, and 95.32°. 



