These last-named auxiliary unarmed boats form an essential part of the system.
In all probability the enemy have by this time thrown stones and other obstacles, and placed infernal machines round the detached fort, to impede a close approach. They cannot, however, have covered a very large surface, so that, with some previous sounding, an approach may be found and a position taken up.
The auxiliary boats should therefore have strong bottoms under the engine-room, and the rest of the body be so subdivided into compartments that they would be proof against serious damage from rocks and infernal machines, and be able to run in under fire and ascertain if obstructions exist, and find the channel if they do.
A battery of such guns could be placed at various points out of range, say at 3,000 yards, at which distance they would hardly attract attention by daylight, and would not be visible in the twilight of night, and could then be concentrated in a few minutes at the point selected for attack within safe breeching distance, say 250 yards; and, if twenty-four shot per minute, of 200 lbs. to 250 lbs. each, thrown with a full charge at 250 yards, can be directed against a small surface of any stone wall yet built (which is pierced with embrasures), the effect ought to be great and rapid. I believe, moreover, that the means of directing the aim will be so effective that if the embrasures can be seen a shell or shot may always be sent in with certainty at 250 yards, and the enemy’s guns dismounted.
Such vessels can rapidly change their position, retreat or advance, be replaced by fresh ones, or withdrawn altogether.
The means of transport of such vessels to the seat of war, although a secondary consideration, has been considered.
They might easily be placed in an outer shell of iron of a good form, which could be rigged complete, and so constructed as to give up its burden when arrived in the seas where it is to act—in fact, a ship of the class of small screw colliers, made to open at the bows and its contents floated out ready for action; but the gun-boat itself, when lightened of ammunition, and the gun lowered to the bottom as ballast, and fitted up with bulwarks, and a light movable iron chamber, forming a water-tight forecastle-deck reaching back, say 30 feet, and schooner-rigged, will, I undertake to say, make a very fair sea boat. Probably no compasses could be ‘corrected’ to be trusted to in such a mass of iron, but a compass fixed to the mizenmast, say at 30 feet from the deck, would be all that could be required.
Immediately abaft the hood or gun-chamber there would be a space under cover from shot where a companion and skylight could be fitted up when at sea, and through which light and air could be obtained at all times when fitted for service.
The funnel, if ever used when the vessel is not in action, would be removed for fighting, and the steam and smoke ejected through an oblique aperture right aft.
The only point to be determined by experiment is whether a moderate thickness of iron of the best quality will stand heavy shot at short range striking very obliquely, say at the worst at an angle of 30 degrees.