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



Construction of Manometer. 



The final form o£ the manometer is shown in fig. 1. The 

 membrane a is stretched and clamped between two circular 



Ear. 1. 



C^ 



PZ" 



•V* 



flj 



cast-iron rings o. The method of uniformly stretching and 

 clamping the membrane varies with the different materials 

 used. 



Method (i.). For use with thin metal sheets or cyclostyle 

 paper : — 



In one of the circular cast-iron rings a circular V groove 

 is turned, and on the other a corresponding V projection. 

 The membrane on being placed between the two ring?, which 

 are subsequently bolted together, is thus stretched as well as 

 clamped. 



Method (ii.). For use with the animal membrane : — 



One of the rings has its temperature raised to about 80° C. 

 and its surface covered with a thin layer of " picei'n *, ?> 

 which is plastic at that temperature. The membrane is then 

 placed in position and uniformly stretched. In this con- 

 dition its surface is carefully damped all over with a wet 

 sponge. This causes the membrane to expand and become 

 slack ; the slackness is removed by gently pulling at the 

 circumference, the " picein" being sufficiently tacky to keep 

 it adhering to the ring during this process. The second ring 

 is then placed upon the first, and the two are firmly bolted 



* Walter, Ann. d. Physik, Bd. xviii. p. 860 (1905). 



