The ‘Treatise on Tactics,’ by the Emperor Leo VI., carries back the record of the means employed against an enemy in naval warfare to the ninth century. The things he recommends as most effective are: cranes, to let fall heavy weights on the enemy’s decks; caltrops, with iron spikes, to wound his feet;[96] jars full of quicklime, to suffocate him; jars containing combustibles, to burn him; jars containing poisonous reptiles, to bite him; and Greek fire with its noise like thunder, to frighten as well as burn him.[97] Many of these methods were of immemorial usage; for Scipio knew the merits of jars full of pitch, and Hannibal of jars full of vipers.[98] Nothing was too bad for use in those days; nor can it be ascertained when or why they ceased to be used. Greek fire was used with great effect in the sea-battles between the Saracens and Christians; and it is a fair cause for wonder that the invention of gunpowder should have so entirely superseded it as to cause its very manufacture to have been forgotten. Neither does history record the date of, nor the reason for, the disuse of quicklime, which in the famous fight off Dover in 1217 between the French and English contributed so greatly to the victory of the latter.[99] It is difficult to believe that sentiments of humanity should have caused these methods to be discarded from maritime hostilities; but that such motives led to a certain mitigation in the use of fire-ships appears from a passage in Captain Brenton’s ‘Naval History,’ where he says: ‘The use of fire-ships has long been laid aside, to the honour of the nation which first dispensed with this barbarous aggravation of the horrors of war.’ That is to say, as he explains it, though fire-ships continued to accompany the fleets, they were only used in an anchorage where there was a fair chance of the escape of the crew against which they were sent; they ceased to be used, as at one time, to burn or blow up disabled ships, which the conqueror dared not board and carry into port, and which were covered with the wounded and dying. The last instance in which they were so used by the English was in the fight off Toulon, in 1744; and their use on that occasion is said to have received merited reproach from an historian of the day.[100]