t.

BALLINASLOE, a market town of county Galway, Ireland, in the east
parliamentary division, 91 m. W. of Dublin, on the Midland Great Western
main line. Pop. of urban district (1901) 4904. The river Suck, an affluent
of the Shannon, divides it into two parts, of which the eastern was in
county Roscommon until 1898. The town contains remains of a castle of
Elizabethan date. Industries include brewing, flour-milling, tanning,
hat-making and carriage-building. Trade is assisted by water-communication
through the Grand canal to the Shannon. The town is widely celebrated for
its great annual cattle-fair held in October, at which vast numbers of
cattle and sheep are offered or sale. Adjoining the town is Garbally
Castle, the seat of the earl of Clancarty, into the demesne of which the
great fair extends from the town.

BALLISTICS (from the Gr. [Greek: ballein], to throw), the science of
throwing warlike missiles or projectiles. It is now divided into two
parts:--_Exterior Ballistics_, in which the motion of the projectile is
considered after it has received its initial impulse, when the projectile
is moving freely under the influence of gravity and the resistance of the
air, and it is required to determine the circumstances so as to hit a
certain object, with a view to its destruction or perforation; and
_Interior Ballistics_, in which the pressure of the powder-gas is analysed
in the bore [v.03 p.0271] of the gun, and the investigation is carried out
of the requisite charge of powder to secure the initial velocity of the
projectile without straining the gun unduly. The calculation of the stress
in the various parts of the gun due to the powder pressure is dealt with in
the article ORDNANCE.

I. EXTERIOR BALLISTICS.

In the ancient theory due to Galileo, the resistance of the air is ignored,
and, as shown in the article on MECHANICS (s. 13), the trajectory is now a
_parabola_. But this theory is very far from being of practical value for
most purposes of gunnery; so that a first requirement is an accurate
experimental knowledge of the resistance of the air to the projectiles
employed, at all velocities useful in artillery. The theoretical
assumptions of Newton and Euler (_hypotheses magis mathematicae quam
naturales_) of a resistance varying as some simple power of the velocity,
for instance, as the square or cube of the velocity (the quadratic or cubic
law), lead to results of great analytical complexity, and are useful