240 
PRINCIPLES OE GUNNERY. 
Object of 
the experi¬ 
ments. 
Bashforth’s 
conclu¬ 
sions. 
Cubic law 
retained for 
convenience 
of calcu- 
lation. 
Mayer sin’s 
experi¬ 
ments. 
Influence 
of tbe form 
of the pro¬ 
jectile upon 
the resist¬ 
ance. 
The object of these experiments was to determine whether the 
resistance of the air varied as the cube of the velocity for all velocities 
between 900 f.s. and 1700 f.s., and whether it varied also as the square 
of the diameter of the projectile. 
The results showed that the resistance of the air for the same velo¬ 
city and the same form of projectile, whether spherical or elongated, 
varies exactly as the square of the diameter of the projectile; also that 
the resistance of the air varies as the cube of the velocity only for velo¬ 
cities between 1100fs. and 1350f.s. 
The cubic law is not nearly correct for velocities between 900 f.s. 
and 1100 f.s.: the resistance of the air between these velocities varies 
approximately as the sixth power of the velocity. 
The cubic law, again, is not correct for velocities above 1350 f.s.: 
the resistance of the air above this velocity varies approximately as 
the square of the velocity. 
Bashforth's conclusions are, then, that 
between the velocities of 900 and 1100f.s.... R oc v G , approximately, 
,, « 1100 and 1850 f.s.... R oc v s , „ 
above 1350 f.s... R <x v 2 . „ 
Since the cubic law of resistance offers the greatest simplicity of 
calculation, Bashforth retained it for convenience as the basis for the 
calculation of remaining velocities, and represented the resistance of 
the air by an expression of the form cv s ; where the coefficient c is 
variable, depending upon the form of the projectile and upon the velo¬ 
city with which it moves. 
Experiments on the resistance of the air to elongated projectiles in 
motion were made at St. Petersburg in 1868 and 1869, under the 
superintendence of General Mayevski, by means of two Boulenge 
chronographs. Mayevski supplemented his experiments by using the 
coefficient of resistance deduced by Bashforth, and adopted a method 
of calculation* of the trajectory of a projectile on the suppositions 
(which he considered borne out by the experiments) that 
between the velocities of 1670 and 1180f.s.... R oc v 2 , approximately, 
a „ 1180 and 918 f.s.... R oc v G , „ 
below 918 f.s... R oc v 2 + » 4 , „ 
The calculations on these suppositions are not so simple as those 
obtained by using Bashfortffis method of formulating the results of 
his experiments. 
The resistance experienced by a projectile in motion through the 
air is influenced by its form or shape —more especially by the shape of 
its fore part, which meets the air, although the shape of its hinder part 
has some influence on the resistance. The form which would theo¬ 
retically encounter the least resistance in passing through the air is 
given by Piobert, in his ‘ f Cours d'Artillerie,” p. 15. 
^ Vide “ Traite de Balistique Exterieure,” par N. Mayevski. Paris, 1872. 
