As early as 1579 an English gunner named William Bourne patented a submarine boat of his own invention fitted with leather joints, so contrived as to be made smaller or larger by the action of screws, ballasted with water, and having an air-pipe as mast. The Campbell-Ash submarine tried in 1885 was on much the same principle. Cornelius van Drebbel, an ingenious Dutchman who settled in England before 1600, produced certain submersible vessels and obtained for them the patronage of two kings. He claims to have discovered a means of re-oxygenating the foul air and so enabling his craft to remain a long time below water; whether this was done by chemical treatment, compressed air, or by surface tubes no record remains. Drebbel’s success was such that he was allowed to experiment in the Thames, and James I. accompanied him on one of his sub-aquatic journeys. In 1626 Charles I. gave him an order to make “boates to go under water,” as well as “water mines, water petards,” &c., presumably for the campaign against France, but we do not hear of these weapons of destruction being actually used upon this occasion. [Illustration: _The “Holland” Submarine Boat._] These early craft seem to have been generally moved by oars working in air-tight leather sockets; but one constructed at Rotterdam about 1654 was furnished with a paddle-wheel. Coming now nearer to our own times, we find that an American called Bushnell had a like inspiration in 1773, when he invented his famous “Turtles,” small, upright boats in which one man could sit, submerge himself by means of leather bottles with the mouths projecting outside, propel himself with a small set of oars and steer with an elementary rudder. An unsuccessful attempt was made to blow up the English fleet with one of these “Turtles” carrying a torpedo, but the current proved too strong, and the missile exploded at a harmless distance, the operator being finally rescued from an unpremeditated sea-trip! Bushnell was the author of the removable safety-keel now uniformly adopted.