As already stated, the great majority of the ships built for mercantile purposes were intended to be able to give a good account of themselves if they should be assailed by a hostile vessel, a contingency which was not at all unlikely in the days when ships roved the seas under the protection of letters of marque and made “mistakes” as to the nationality of the prize when the prospective booty might be held to justify the error. Before the nations took to building vessels especially for war every merchant was liable to have his traders requisitioned for war purposes, and even up to the end of the nineteenth century the inclusion of armed merchantmen in national forces was not uncommon. Letters of marque were permits granted to ship owners whose vessels had been despoiled by the subjects of another nation to recoup themselves at the cost of any vessels belonging to that nation which they could capture, and to continue to do so until the losses were made good. Naturally they found this profitable, much more so indeed than ordinary trading, and did not hesitate to set a low value upon all captures when casting about to find an excuse for another expedition. Piracy, too, was rife, and as at sea every shipmaster was a law unto himself unless there was someone at hand to enforce a change of views, the shipmaster or merchant turned pirate usually nourished exceedingly until captured red-handed, when his shrift was like to be a short one. As an instance of the license to which this liberty was extended, may be mentioned the Barton family who, in the fifteenth century, had granted to them letters of marque to prey upon the Portuguese in retaliation for the murder of John Barton, who was captured and beheaded by Portuguese. His sons conducted the enterprise with such thoroughness that they were able to pay their Scottish Royal master so well that they were never interfered with by him, and when he entrusted them with the task of reducing the Flemish pirates who levied toll on Scottish commerce, they sent him a few barrels filled with pickled human heads to show that they were not idle. The fame of this Scottish family became world wide, for they had now a powerful fleet and traded and fought and captured where they would, so that the reputation of the Scottish navy was great. One of the ships of the Barton family, the _Lion_, was second in size and armament only to the _Great Harry_ itself. The death of Sir Andrew Barton is commemorated in a well-known ballad.