10 
MINUTES OF PROCEEDINGS OF 
screens placed in the direction of the ball's flight, we can determine the line 
of fire, and consequently the length passed over in the cylinder, we can 
estimate the velocity of the ball in its movement across the apparatus. The 
precision by this means depended upon the size of the diameter of the 
cylinder, as well as the rapidity and uniformity of rotation that was given to 
it. The velocity of rotation was obtained by a weight descending into 
a well. 
Matkei’s Machine of Rotation. 
A 
The velocity with which the shot passes through the diameter of the 
cylinder, and consequently its uniform velocity during one second of time, 
is found as follows :— 
Let D be the diameter of the cylinder, C its circumference, t the time 
that it takes to make one revolution, m the distance that a point of the 
circumference turns while the shot is traversing the diameter, then 
the last term will express the space passed through by the shot with a 
uniform velocity during one revolution of the cylinder; then, expressing 
by V the space that the shot passed through with a uniform velocity in 
one second, or its initial velocity, 
CD CD 
f • 1 •* • # } 
m tm 
the last term = V will express the velocity sought. 
In general, the cylinder turned with an equable motion of l=f of a 
second, D — 10 feet, consequently C = 31*42 feet; substituting these 
Values in the expression for the velocity, 
and supposing m to be found by experiment equal to i of a foot, 
V = 1571i 
