PRESSURE GAUGES. 



21 



cylinder. All these instruments should be checked by com- 

 parison, by studying the effects of well-known pressures and 

 drawing up corresponding tables. 



4. The spring dynamometer of Le Boulenge may be mentioned, 

 and the manometric balances of Marcel Deprez based on 

 opposite pressures. An account of them will be found in the 

 " Traite sur la poudre " already quoted (p. 572). 



In the same work will also be found a description of the 

 apparatus founded on the dynamic method, such as the experi- 

 ments made with the ballistic pendulum by Cavalli (1845-1860), 

 and by Neumann (1851), the use of Schulze's chronographs 



Fig. 1. 



(1864), Noble (1872), Noble and Abel (1874), the use of the 

 ballistic pendulum fitted with a metallic plate to measure 

 the effect of impact, by Ph. Hess, and the other similar ap- 

 paratus invented by that learned Austrian officer (1873-1879), 

 the use of Captain Eicq's recorder (1873), that of the Boulenge 

 monograph, of the accelerometer and accelerograph of Marcel 

 Deprez and Sebert (1873-1878), that of the velocimeter due to 

 Sebert, a learned officer to whom we owe so many ingenious 

 inventions, etc. However noteworthy these instruments may 

 be, their description would carry us too far, and it does not 

 enter into the scope of the present work. 



