THE ROYAB ABTIBBEBY INSTITUTION. 
15 
9. Mr Bobins was the first who took advantage of this idea, and con¬ 
structed his celebrated ballistic pendulum, in which he imparted the 
velocity lost by the projectile to a large block of wood suspended by an 
axis, about which it was free to move in the direction of the shot's 
motion. 
Robins ' Ballistic Pendulum . Eig. 5. 
10. Bobins' ballistic pendulum consisted of a broad plate of iron, on 
which was bolted a wooden plank about nine inches square. It was 
suspended by means of a wooden shaft and axis, the extremities of which 
rested in sockets screwed into the upper ends of two poles, a third pole 
formed with these a tripod, which supported the whole apparatus. Near 
the bottom of the two poles a brace was fastened, having a contrivance 
fixed to it, through which a ribbon ran with very slight friction. One end 
of this ribbon was made fast to the pendulum, and the other end lay on the 
ground. 
Hobms’ Ballistic Pendulum, 1748. 
Pig. 5. 
When the gun was fired, the ball struck the pendulum, causing it to 
oscillate and pull out the ribbon. The length pulled out corresponded 
to the vibration of the pendulum, and consequently to the force of the blow 
it had received. Erom this was computed the velocity of the ball. 
11. The invention of the ballistic pendulum by Mr Bobins is an 
epoch in the history of the science of gunnery. He was the first who 
seems to have entered upon this subject with the determination to grasp 
the many difficulties with which it was surrounded. Previous to Bobins' 
time, the most erroneous theories had been advanced by many philosphers. 
Thus, Galileo, in the fourth of his Dialogues on Motion, 2nd Edition, 
p. 384, demonstrated that a projectile in its flight would describe the 
curve of a parabola, excejot so far as the resistance of the air should cause it 
to deviate ; but Galileo formed a very inadequate estimate of the amount of 
this resistance. Mr Bobert Anderson, in his “ Genuine Use and Effects of 
the Gunne," published in 1674, and also in “ To Hit a Mark," published in 
1690, adopts this theory of Galileo without any modification. 
