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BALLIOL COLLEGE. pleted the scheme and gave the college its first statutes. It was long comparatively unimportant. Although Wiclif became its master about 13G0, it was for a while the home of the champions of the scholastic philosophy. In the Fifteenth Century it became 'the nursing-mother of the early English humanists,' such men as Humphrey. Duke of Gloucester, and John Tiptoft, Earl of Worcester, being num- bered among its scholars. After this period of brilliance, Balliol was little heard of until the Nineteenth Century, when it came once more to the front. It was blessed with a succession of able masters, of whom the most famous was Benjamin .Towett : it received many notable bene- factions, particularly the Snell Exhibitions, which have attracted many brilliant Scotchmen, among them Adam Smith, Sir William Hamil- ton, and J. G. Lockhart: and. at the same time that it set the example (with Oriel) of open- ing its scholarships to general competition, it established a rigid standard of ability for its members, by requiring from them an addi- tional entrance examination and obliging them to read for henors in the schools. The college consists of a master, 12 fellows, about 50 scholars and exhibitioners, and nearly 200 other undergraduates. Its buildings date from the library, part of which is as old as 1430, to the present hall, completed in 1877. It has a long list of distinguished graduates, particularly in the Nineteenth Century. Among poets and men of letters, it can boast of Southey, Matthew Arnold, Swinburne, Clough, Andrew Lang, and Calverley, besides having associated to itself Robert Browning as an honorary fellow. To the Oxford Movement it contributed Cardinal Manning and William George Ward; and, to the English Church, two of its primates, Tait and Temple. And more than one of the intel- lectual and social movements specially character- istic of the end of the Nineteenth Century owe their inspiration to T. H. Green, fellow of Balliol from 18(10 and afterwards professor of moral philosophy.

BALLIS'TA. See Artillery.

BALLIS'TIC PEN'DULUM. See Ballis- tics.

BALLISTICS {Ballista, an engine for hurl- ing missiles — I>at. from Gk. (}d'/,?teiv, ballein, to throw). The science which treats of the mo- tion of heavy bodies projected into space. Its usual meaning is, however, restricted to the motion of projectiles of regular form, fired from cannon or small arms. The subject, con- sidered as a branch of the science of gunnery, is divided into Inlcrior liullistics, which treats of the motion of the projectile inside the bore of the gun: Exterior Ballistics, which treats of the motion of a projectile between the muzzle of the gun and the object it strikes ; and Ballistics of Penetration, which treats of the effects of the projectile upon the object it strikes.

Interior Ballistics. In interior ballistics, we calculate the velocity of translation and rota- tion which the combustion of a given charge of powder, of known composition and quality, will impart to a given projectile, and the effect upon the gun. The following definitions w^ill enable the nontechnical reader to appreciate better some of the problems with which this science deals:

The Specific Gravity of powder is the weight of a given volume of powder referred to that of an equal volume of water.

Gravimetric Density is the density of the powder when the spaces between the grains are considered.

Explosion is the rapid conversion of powder into gases and solids with evolution of heat. It may be divided into three parts: Ignition, which is the setting on fire of a part of the grain or charge; Inflnmmation, which is the spread of the ignition from point to point of the grain or charge; and Comhustion, which is the burning of the inflamed grain or charge from the point of ignition.

Velocity of Emission is the rate of evolution of the gas of gunpowder.

A Progressive Poioder is one that burns slowly at first and more rapidly afterwards. Density of Loading is the ratio of weight of the charge of powder to that weight of water, at its maximum density, which will completely fill the volume in which the charge is fired. The Force of the powder is the pressure per unit of surface exerted by the gases from the unit weight of powder, the gases occupying at the temperature of explosion a volume equal to imity.

The Passive Resistances are those due to the forcing of the band of the projectile into the grooves of the rifling, friction, etc. The Ballistic Coefficient, 'C,' for a given pro- jectile depends upon the cross - section and weight of the projectile and the density of the air, and measures the ballistic efficiency of the projectile.

The Factor of Effect is the ratio of the actual work realized by the projectile at the muzzle to the entire work of the charge.

The Energy of the projectile means its power to do work, and is proportional to its weight and the square of its velocity.

History. It is only within the last fifty years that the complicated phenomena which take place within the bore of the gun when the charge is fired have been clearly comprehended. The celebrated Benjamin Robins (1740), else- where referred to in this article, made many experiments relating to interior ballistics. His de- ductions from his experiments, in spite of the ex- tremely erroneous and sometimes absurd opinions on the subject that were entertained in those days, justly entitle Robins to be called the 'father of modern gunnery.' Dr. Button's experiments verify most of Robins's deductions, dift'ering principally in the estimate of maximum tem- perature and pressure. D'Arcy (171)0) made the first attempt to determine dynamically the law of pressure of gases in the bore of a musket by measuring the velocity of the projectile at different points of the bore. His method was successively to shorten the barrel, and measure; for each length, the velocity of the bullet by means of a ballistic pendulum. From these velocities he got the corresponding accelera- tions, and then the pressures by nuiltiplying the accelerations by the mass. Count Rimiford (1792) made the first attempt to measure di- rectly the pressure of fired gunpowder. The account of his experiments was the most im- portant contribution to interior ballistics which had been made up to that time. His appara- tus consisted of a small wrought-iron mortar,