_Gunpowder._—A mixture of saltpetre, charcoal, and sulphur, which explodes. The signs of its explosion are a bright flash, a loud noise, and a large volume of smoke. _Incendiary_ (for “incendiary composition”).—A substance or mixture which burns progressively, although fiercely, and is hard to put out. _Machine_ always means an apparatus of the ballista type. _Cannon_ includes bombards, mortars, guns, &c. _Musket_ includes all hand firearms charged with gunpowder. II Of the many difficulties that beset the present inquiry, two deserve special mention. The first is the want of simple exactness in most early writers when recording the facts from which we have to draw our conclusions. At times their descriptions are so meagre that it is difficult, if not impossible, to decide whether certain projectiles were incendiary or explosive. At other times they abound in tropes and figures of speech which amount to an unintentional _suggestio falsi_. “The missiles spread themselves abroad like a cloud,” says a Spanish Arab; “they roar like thunder; they flame like a furnace; they reduce everything to ashes.”[1] A projectile full of blazing Greek fire appeared to Joinville to be of portentous bulk. It flew through the midnight sky with thundering noise like a fiery dragon, followed by a long trail of flame; and it illumined the whole camp as with the light of day.[2] Even to approach the truth, we must prune such figures of rhetoric; and this is a dangerous operation, for we may prune too much. The only safeguard against these suggestive metaphors is to keep steadily in view the distinctive peculiarities of incendiary and explosive projectiles. The incendiary shell was simply an envelope intended to convey into the interior of a fort, ship, &c., a quantity of combustible matter, which burned with such violence as to _set fire_ to everything inflammable that was near it. The primary object of the explosive shell, on the other hand, was to _blow up_ whatever it fell upon. It might occasionally, by the intense heat generated by the explosion,[3] set fire to its surroundings when inflammable; but this was a mere incidental consequence of its action. Its aim and end was to explode. When a musket or cannon was fired there was a bright flash, a loud, momentary report, and a large volume of smoke.[4] When an incendiary missile was discharged from a machine there was no flash, but little smoke, and the only sounds were the whizzing and sputtering of the burning mixture and the creaking and groaning of bolts, spars, ropes, &c.:— “With grisly soune out goth the greté gonne.”[5]