CHAPTER II.--ON GUNPOWDER.

Origin of its invention--Roger Bacon’s recipe--Accidental discovery by a German monk--Gunpowder introduced by the Saracens--Its explosive and propellant properties--Composition of gunpowder--Nitre its essence--Properties of sulphur as an ingredient--Proportions and constituents of French gunpowder--Sulphur not always indispensable-- Chemical principles of its composition--Component parts of different gunpowders--Source of its explosive force--Explosion at Gateshead-- Variations in strength and quickness of fire--Granulation of sporting gunpowder and of artillery gunpowder--Importance of suitable granulation for different firearms--Large grain powder the more effectual expellant--Fine powder dangerous--Principle of granulation-- Gun-cotton--Imperfect instrument for testing gunpowder--Charcoal-- Operation of making gunpowder described--“Glazing” detrimental-- Utility of granulation--Fine grain powder--Dr. Ure on the projectile force of gunpowder--Dr. Hutton’s calculations and experiments--Mode of controlling the destructive force of gunpowder--Experiments to test the velocity of explosive force of different granulations--The grain should be proportioned to the length and bore of the gun--Chlorate of potassa used by the French in making gunpowder--Similar powder proposed by Mr. Parr, and condemned by Sir William Congreve--Velocity in projectile force must be gradual--Curious experiment--Operation of blasting stone, &c., with gunpowder--English sporting gunpowder-- Military and naval gunpowder--Fame of English gunpowder makers 18