softer, cannot be driven firmly home into hard wood as an iron bolt can. But, on the other hand, iron fastenings are apt to corrode rapidly, and an old iron-fastened vessel is likely to be nail-sick and to require refastening.
It must not be forgotten, too, that copper and iron, when immersed together in sea-water, set up galvanic action; so that if an iron-fastened vessel be coppered, even though the greatest care was taken to prevent contact between the metals when the sheathing was put on, the insidious galvanic action may be at work in places, and the corrosion of the iron nails will be revealed by the presence of iron-rust stains at the junctures of the copper plates. Again, if, as sometimes happens, the sheathing has been brought down into close proximity with the iron keel, the bolts holding the keel may be eaten through, and cases have been known of a vessel's keel falling off when she is under way, in consequence of the unsuspected corrosion of the bolts from this cause. So, too, is it when lead and iron come into contact. Look to the fastenings of the lead keel, if there be one, for if, as is often the case even with copper-fastened vessels, the floor-bolts be of iron, galvanic action may have been set up between the bolts and the lead ballast, and an examination may lead to the timely discovery that the bolt-heads are rotted through, and are ready to fall off.
The great strain of a vessel's rigging comes upon
