184 



EXPER I M KNTA L PI I YS [( >L( )< i V 



constant pressures. This method gives far more accurate results than the- 



mercury manometer, hut possesses certain disadvantages. 



There are two instruments which are employed for the purpose. The 

 first of these is Fick's spring kymograph, fig. 145. 

 It consists of a C-spring, a, made of thin strips of 

 metal united at their edges. If the pressure in the 

 space thus caused be increased the spring opens 

 out. It possesses little inertia, and therefore re- 

 sponds quickly to changes of pressure. Fig. 146 gives 

 a small piece of tracing taken with this manometer. 

 Recently a modification of this kymograph by v. 

 Basch has been introduced in which the C-spring. 



is reduced to the smallest size. It gives very excellent results. 

 The other instrument is Hiirthle's rubber manometer. 



Fig. 146. 



Fig. 147. — Hurthle's Manometer. 



