Mr. J. D. Fry on a New Micromanometer. 499 



In one of the calibrators used in obtaining the calibration 

 curves below, the limbs of the U-tube were 15 cm. long^ and 

 the temperatures of the two limbs were 0° C. and 15° 0. 

 respectively. This gives a pressure difference of about one 

 dyne per cm. 2 with the U-tube in a vertical position. 



Curves I. and II. show calibrations of the same manometer 



Curve I. 



22 



20 



& 



m 



/ 



o>2 



O'gt 



O-G 



0-8 



jL-O 



under different conditions of sensitiveness. The pressures 

 are in dynes per cm. 2 , and the gauge readings deflexions of 

 a spot of light on a centimetre scale placed one metre from the 

 instrument. Curve I. was obtained with the manometer in 

 an unsensitive condition, the application of a pressure differ- 

 ence of 1 dyne per cm. 2 producing a deflexion of about 



2M2 



