Sir William Monson’s device of a bark, with an under-water cannon and an accompanying boat was soon developed by the English navy into the more practicable mine, self-contained and floating, to be towed by boat or submarine. In January, 1626, the King gave a warrant to the Master of the Ordnance, ‘for the making of divers water-mines, water-petards, and boates to goe under water.’ In June of the same year, the Duke of Buckingham, then commanding the naval expedition for the relief of La Rochelle, issued a warrant ‘for the delivery of 50 water-mynes, 290 water-petards, and 2 boates to conduct them under water.’ Pepys in his ‘Diary’ for March 14, 1662, mentions a proposal by Kuffler of an ‘engine to blow up ships.’ He adds, ‘We doubted not the matter of fact, it being tried in Cromwell’s time, but the safety of carrying them in ships;’ and probably this distrust of Drebbel’s German subordinate proved to be justified, for nothing more is heard of the design. The attempt referred to as made ‘in Cromwell’s time’ may have been Prince Rupert’s attack on Blake’s flagship, the _Leopard_, in 1650. The engine then used was not a submarine one but an infernal machine, concealed in an oil-barrel, brought alongside in a shore boat by men disguised as Portuguese, and intended to be hoisted on board the ship and then fired by a trigger and string. A more ingenious ‘ship-destroying engine’ was devised by the Marquess of Worcester in 1655. This was evidently a clock-machine, for it might be affixed to a ship either inside, by stealth, or outside by a diver, ‘and at an appointed minute, though a week after, either day or night, it shall infallibly sink that ship.’ The clock machine was actually first tried in action in 1776 by Bushnell, or rather by Sergeant Lee, whom he employed to work his _Turtle_ for him. The attack by this submarine upon the _Eagle_, a British 64-gun ship lying in the Hudson River, was very nearly successful. The _Turtle_ reached the enemy’s stern unobserved, carrying a mine or magazine of 150 lbs. of powder, and provided with a detachable wood-screw which was to be turned until it bit firmly on the ship’s side. The mine was then to be attached to it, and the clockwork set going. The wood-screw, however, bit upon some iron fittings instead of wood, and failed to hold; the tide also was too strong for Lee, who had to work the wood-screw and the propeller at the same time. He came to the surface, was chased by a guard-boat, and dived again, abandoning his torpedo, which drifted and blew up harmlessly when the clockwork ran down. Lee escaped, but the _Turtle_ was soon afterwards caught and sunk by the British. Bushnell himself, in the following year, attacked the _Cerberus_ with a ‘machine’ consisting of a trigger-mine towed by a whale-boat. He was detected, and his mine captured by a British schooner, the crew of which, after hauling the machine on deck, accidentally exploded it themselves, three out of the four of them being killed.