237 
PRINCIPLES OF GUNNERY. 
RIFLED ORDNANCE. 
by 
CAPTAIN J. SLADEN, K.A. 
PROFESSOR OF ARTILLERY, R.M. ACADEMY, WOOLWICH. 
{Continued from p. 65.) 
CHAPTER V. 
Resistance to the Motion op Projectiles in the Aifi. 
Resistance of the Air.—Robins’ Experiments.—Hutton’s Experiments.—Hutton’s Law.—Didion’s 
Law.—Welter’s Law.—Helie’s Law.—Bashforth’s Experiments.—Report of Committee of 
Reference on Bashforth’s Experiments.—^Advantage of Bashforth’s Method of Experimenting.— 
Object of the Experiments.—Bashforth’s Conclusions.—Cubic Law retained for Convenience of 
Calculation.—Majevski’s Experiments.—Influence of the Form of the Projectile upon the 
Resistance.—Experiments to Determine the amount of Resistance of the Air to Different 
Forms of Heads of Projectiles,—Results of Experiments.—The Resistance of the Air to a 
Projectile in Motion.—The Retardation varies directly as the Resistance opposed to the Motion 
of the Projectile, and inversely as the Weight of the Projectile.—Equation of Motion con¬ 
necting Distance and Velocity.—Approximate Calculation of Remaining Velocity with regard 
to Range.—The Value of . the Coefficient K varies at Different Velocities.—Explanation and 
Use of the Table of Values of the Coefficient K .—Table connecting Distance and Velocity.— 
The Power which a Projectile in Motion has of maintaining its Velocity.—Equation of Motion 
connecting Time and Velocity.—Approximate Calculation of Remaining Velocity with 
regard to Time.—Distance and Velocity Table.—Time and Velocity Table.—Explanation of 
Tables I. and II.—Equation (L), connecting Distance and Velocity.—Equation (II.), con¬ 
necting Time and Velocity.—Examples in the Solution of Problems in Practical Gunnery by 
means of Tables I. and II. 
The resistance of the air to projectiles moving in it with high velo- Resistance 
cities has long been known to be very considerable, and many attempts oftheair - 
have been made to find a law which would account for the results 
observed in practical gunnery. 
Bobins* experiments in 1742 are the first recorded attempts to Robins’ e *> 
obtain the law of the resistance of the air to projectiles moving with P enments ‘ 
high velocities. He fired spherical leaden bullets from a small-arm, 
and by means of the ballistic pendulum deduced the following general 
statements :—(1), that till the velocity of the projectile exceeds 1100 f.s., 
the resistance of the air may be taken to be as the square of the velocity; 
(2), that at the velocity of 1100 f.s. (nearly the same as that with 
which sound is propagated through the air), this law of the resistance 
is altered; (3), that if the velocity exceeds 1100 f.s., then the absolute 
quantity of that resistance in these greater velocities will be nearly 
30 
