128 Cincinnati Society of Natural History. 



projectile in its ])assage between two given points. Henry's chro- 

 nograph provides against every instrumental error. Terminal 

 pairs of wires from a number of different pairs of screens, through 

 which the projectile passed, would send sparks which perforated the 

 graduated paper covering the recordingcylinder, and impressed their 

 marks ; thus, the velocity of the projectile, in all required points in 

 its i)ath, may be determined by a single experiment. He visited 

 Maj. Mordecai during his ballistic experiments at the Washington 

 Arsenil and told him that velocities could be best determined by 

 electricity. 



Capt. Schultz of the Frencji army combined a method of graph- 

 ically recording vibrations of a tuning-fork with Helmholtz's way 

 of making them isochronous and Henry's cylinder and induction 

 spark, and produced an apparatus capable of meeting every demand 

 required in the solutions of questions in regard to this subject — 



Proof of gunpowder, 



Hygrometrical test. 



Proportion of ingredients, 



Mode of manufacture. 



Density, 



Size of grains, 



Charges for guns, 



Cartridges for cannon, 



Windings of balls, 



Loss of force by the vent, 



Effects of wads, etc. 

 In a X inch gun, loo inches in length, the total time required 

 for the projectile to reach the muzzle is ■^\-^ of a second. 

 Records are obtained from the chronoscope of the time required for 

 the passage of the shot, between two points in the gun only 2.7 

 inches apart. 



If you desire to estimate the strain on the gun, or the cpian- 

 tity of motion imparted to a projectile, we know that if the mean 

 pressure (P) of the gas be multiplied by the space (S) passed over 

 by the projectile in acquiring its velocity, the result will be the 

 measure of the work done by the charge of powder ; and it will be 

 equal to the work of stopping the same projectile, no matter how 

 or by what means it may be done. 



The same result is obtained by measuring the velocity impar- 

 ted to the projectile under the circumstances mentioned, and mul- 



