HISTORY OF MARINE ARCHITECTURE.

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The situation of particular harbours, owing to points of land, to the setting oftides, to rocks, shoals, or sands, which vary in their position, their forms, andother circumstances as much as the harbours themselves, frequently preventships and vessels from approaching so sufficiently near to towns and fortressesas to afford any well-founded assurance of success, in case of attack. The prin-cipal impediments have generally proceeded from the great depth of water whichthe vessels have required, owing to the sharp construction of the hull, and the con-sequent prevention of their approaching sufficiently near to the proper point. Onsome occasions, where the obstacles have been even less formidable, it has beennecessary to wait For the time of high water, or a spring tide ; a delay whichhas afforded sufficient time for the enemy to recover from the dismay into whichthe sudden approach of an hostile armament had thrown them, and enabledthem to provide means of opposition sufficient to render the attack ineffectual.Exclusive of the first inconvenience which attends the employment of vesselsdrawing much water, as bomb ketches, there is a second equally serious. Shoulda sharp-built vessel even succeed in getting properly to her intended station,and commence the attack with success, if there is not a sufficient depthof water to float her during the whole of the ebb tide, its natural heeling onthe failure of support from the surrounding fluid, will inevitably cause not onlya cessation from attack, but leave the unfortunate object deprived of all meansof defence, and exposed to the most violent efforts of the enemy’s fury : it ismost probable, that it would be either destroyed, or compelled to surrender, erethe return of the flood umuld hold forth a prospect of relief; and should nei-ther of the misfortunes just mentioned take place, it is extremely likely that thewater would flow into the vessel sharply built, as described, instead of floating,and restoring it to its upright position. Vessels, on the contrary, constructedwith flat floors, would not be subject to any of the inconveniences already men-tioned ; their trivial draught of w r ater would, in most instances, enable them topass to, or from the object of attack, at any time ; and, should they even beunlucky enough to take the ground, their upright situation would enable them tocontinue the attack, if within the proper distance, with perhaps as much effectas they could have done, had they remained afloat.

All the same reasons and advantages, pointed out in the preceding instance, arenot only equally applicable in the case of fireships ; but there are also others, inaddition, which may be reasonably expecteffto be derived from the use of vesselsintended to be applied to the destructive purpose just mentioned, if fitted with slidingVol. III. o c keels.