HISTORY OF MARINE ARCHITECTURE.

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tion of brass in its room *. The latter was found to be very little affected bycorrosion, in comparison with the former ; and in addition to its consequentdurability, the grievous evils and misfortunes frequently produced by the planksbecoming iron sick, were totally prevented from taking place. Under thesystem of construction first used, vessels, otherwise in a complete state forservice, became leaky, and to that inconvenience, rapidly increasing till it be-came almost insupportable, quickly succeeded, destruction.

The gallies thus built, being found, after much sad experience, equally inca-pable of resisting the attacks of the human foe, or the assaults of those commonenemies, the waves and the winds, the substitution, already related, naturallytook place, and might be said to prevail in general use till the irruption of theGoths. The destruction of the Roman empire which it produced, then gave, asit were, a natural check to all scientific discoveries, or improvements, and com-pelled mankind, when again emerging from a state little short of barbarism,to commence their researches, as from a state of almost total ignorance.

Close as the junctions between the planks might, through the care of theartificer, be made, the water still found means to force its way between them.To obviate this great inconvenience, the operation now known in Britain bythe term caulking, was adopted. In the early ages of navigation, the methodso strangely misunderstood by some authors, and which, notwithstanding itsbeing an imperfect remedy for the evil, is still partially practised by the Chi-nese -j-, suggested itself as a remedy. The first application consisted of nothingmore than sea-shells in their natural state, which being reduced into a finepowder, and formed into paste with water, was found, on being carefully in-troduced into the chinks, or seams, to exclude the water, when first applied,with a tolerable degree of perfection : having, however, no very strong propensitytowards adhesion, it soon cracked, and, owing to the natural strain of the vessel,falling out by degrees, the water soon found nearly as easy an admission throughthe crevices, as though the operation had never been performed. I he necessityof some alteration, or improvement, gave rise to the very early practice ofburning the shells, and converting them into lime, previous to their mixture.

* Vegetius, lib. iv. cap. 34, speaks of this substitution as having taken place long before his time,.ami assigns, as a very natural cause for the alteration, that biass was so much less liable to corrode thaniron. Such was the practice, according to the testimony of Athenxus also, as far hack as the time ofNero.

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