To transport them Napoleon had collected in the ports of Ostend, Dunkirk, Calais, Ambleteuse, Vimereux, Boulogne and Etaples, 954 transports and 1339 armed vessels--gun-brigs, schooners, luggers, schuyts and prames; and all these light vessels lay snug in their harbours, protected by shoals and sandbanks which our heavier ships of war, by reason of their draught, could not approach.
In particular, a double tier of vessels--one hundred and fifty in all--which were moored outside the pier of Boulogne, and protected by heavy shore batteries, excited while it baulked the rage of our gallant seamen manoeuvring in the deep waters of the Channel.
Strange diseases suggest strange remedies.

Our Admiralty, in the spring of the year, had been approached by an ingenious gentleman with the model of an invention by which he professed himself able to reach these hundred and fifty ships in Boulogne and blow them in air without loss or even danger to our fleet.

This machine consisted of a box, about twenty feet long by three feet wide, lined with lead, caulked, tarred, ballasted and laden almost to the water's edge with barrels of powder and other combustibles.

In the midst of the inflammable matter was placed a clockwork mechanism which, on the withdrawal of a peg, would in a fixed time (within some ten minutes or thereabouts) ignite and explode the vessel.
A dozen of these engines, claimed the inventor, if towed within range and released, to be swept down upon Boulogne pier by the tide, would within a few minutes shatter and dispel the nightmare of invasion.
The Admiralty sanctioned the experiment, news of which had awakened some interest not unmixed with derision throughout the British Fleet; and the business which called the _Vesuvius_ to Portsmouth was to take in tow the first of these catamarans (as our sailors called them) and convey it across to the squadron watching Boulogne.
On the morning after the _Vesuvius's_ arrival, two dockyard boats arrived with the hull of the machine in tow--it resembled nothing so much as a mahogany coffin--and attached her to the _Vesuvius's_ stern by a kind of shoreline.

This done, the officer in charge presented himself on board with the clockwork under his arm, and in his hand a letter for Captain Crang, the first result of which was an order to dress ship.