Perhaps the Admiral is referring to what Lieutenant Sleeman says is the earliest record of the employment of a torpedo (_i.e._, a case of explosion possessing the power of aggression). In 1585 an Italian engineer named Zambelli invented a floating mine and succeeded in destroying a bridge built over the Scheldt by the Prince of Parma. Zambelli’s mine consisted of a flat boat filled with gunpowder arranged in it so as to secure the maximum effectiveness, and provided with a long sulphur metal rope and clockwork for its ignition. A few years before this feat (in 1578) an Englishman, by name William Bourne, published a book entitled, “Inventions or Devices.” He suggested in his seventeenth article, “How for to sink a ship that hath laid you aboard without shooting of ordnance.” William Bourne is in some books said to have actually invented a plunging apparatus for use in warfare, but no circumstantial account of such a vessel is extant. The Marquis of Worcester, in his “Century of Inventions” (1663), describes in section 9 “An engine, portable in one’s pocket, which may be carried and fastened on the inside of the greatest ship, _Tanquam aliud agens_, and at any appointed minute, though a week after, either by day or night it shall irrecoverably sink that ship.” The smallness of the engine suggests some explosive missile connected with clockwork as the only means to insure its being compact and operating on a precise day at a stated point of time. Section 10 is as follows: “A way from a mile off to dive and fasten a like engine to any ship so as it may punctually work the same effect either for time or execution.” In 1596 John Napier of Merchiston wrote a statement of four “Secret Inventions,” concluding with the remark—“These inventions, besides devices of _sailing under the water_ with divers other devices and stratagems for burning of the enemies, by the grace of God, and work of expert craftsmen, I hope to perform.” Pepys in his “Diary,” under date March 14, 1662, says: “This afternoon came the German Doctor Knuffler to discourse with us about his engine to blow up ships. We doubted not the matter of fact it being tried in Cromwell’s time, but the safety of carrying them in ships, but he do tell us that when he comes to tell the King his secret, for none but the Kings successively and their heirs must know it, it will appear to be of no danger at all.” The foregoing extracts show that the possibility of a practical method of submarine attack was beginning to take shape in the minds of philosophers and inventive geniuses. “Fire and Powder Ships,” “Machines,” “Internals,” “Catamarans,” and similar devices for accomplishing the destruction of an enemy were known at this time, and it is not strange that the idea of making the explosion take place _beneath_ the water should have suggested itself. CHAPTER X EARLY EFFORTS IN SUBMARINE NAVIGATION