It is exceedingly probable that the adoption of a new engine of warfare by a tribe would be condemned by another tribe—to whom it had not occurred to use it—as illegitimate, but it is equally probable that while sturdily protesting against the use of one weapon the tribe would be slily endeavouring to procure one more deadly still. The first great revolution in the art of war was the introduction of gunpowder, both as a propelling agent and also as a charge for shells and bombs. Although the explosive nature of saltpetre when mixed with carbon and charcoal was doubtless known to the Chinese some centuries before the Christian era, our first knowledge of the use of gunpowder as a military agent dates from the seventh century, when it was used by the Byzantine emperors under the name of “Greek fire” in the defence of Constantinople against the Saracens. “Greek fire,” the invention of which is commonly attributed to Callinichus in 668 A.D., consisted probably of pounded resin or bitumen, sulphur, naphtha, and nitre. There were three ways of employing it: it was poured out burning from ladles on besiegers, it was projected out of tubes to a distance, and it was shot from _balistæ_ burning on tow, tied to arrows. Its effect was probably rather moral than material. Geoffrey de Vinesauf, in an account of a naval battle in the time of Richard I., writes thus of Greek fire: “The fire, with a deadly stench and livid flames, consumes flint and iron; and unquenchable by water, can only be extinguished by sand or vinegar. What more direful than a naval conflict! What more fatal, when so various a fate envolves the combatants, for they are either burnt and writhe in the flames, shipwrecked and swallowed up by the waves, or wounded and perish by arms.” Despite the lamentations of the humanitarians of the time, Greek fire and serpents (missiles resembling rockets charged with and impelled by the slow explosion of a certain mixture) continued to be used in the navy until the reign of Richard III. Another favourite method of early naval warfare was the “fire-ship.” Falkiner, an old writer, tells us that fire-ships were used by the Rhodians in 190 B.C. They were certainly used by the Greeks; they were employed by ourselves against the Armada, and they first appeared in our Navy List in the year 1675; they were used in the Dutch and French wars at the close of that century, but probably fell into disuse in the eighteenth. It is quite clear that with the French, as well as with ourselves, the crews of fire-ships did not expect quarter. Admiral Gambier deprecated fire-ships as being a “horrible and anti-Christian mode of warfare,” while Lord Cochrane said that if any attempts were made upon the British squadron by fire-ships they would be “boarded by the numerous row-boats on guard, the crews murdered, and the fire-ships turned in a harmless direction.”