PRINCIPLES OF GUNNERY. 
241 
Its length is five times its greatest diameter, and its largest section 
is placed at f tlls of its length from the base.* 
With service projectiles the base is generally flab, but slightly 
rounded at the edges for convenience in loading. 
The total resistance to a projectile moving through the air is due 
(1) to the fore part of the projectile forcing its way through, and so 
displacing the particles of the air which impede its motion; (2) to the 
hinder part being dragged back by suction, owing to a formation of a 
partial vacuum in its rear. 
Experiments were made by Professor Bashforth with the Clock 
Chronograph to ascertain the amount of the resistance of the air to 
different forms of heads of projectiles, the form of the hinder part 
being flat in all. 
Four different forms of head were experimented on—viz., (1) hemi¬ 
spherical head, (2) hemispheroidal head, (3) ogival head of 1 diameter, 
and (4) ogival head of 2 diameters. The object of the experiment was 
to determine which of these forms offered the least resistance to the 
motion of the projectile. 
l. 2. s. 4. 
The results obtained under similar conditions of velocity were as 
follows:— 
Form of head. 
Coefficient of resistance 
K=( 1000)?cx ™ 
d* 
Hemispherical . 
. 132-9 
Hemispheroidal. 
. 104-8 
Ogival-head (1 diam.) . 
. 109-7 
Ogival-head (2 diams.) . 
. 104-2 
• • • TV 
The coefficient c is put into the form K — (1000) 3 <? x ^ for conve- 
Cv 
* Vide Owen’s. " Modern Artillery,” p. 215. . 
Experi¬ 
ments to 
determine 
the amount 
of resist¬ 
ance of the 
air to diff¬ 
erent forms 
of heads of 
projectiles. 
Results of 
experi¬ 
ments. 
