Looking astern, we saw a small clipper-built brig with a black hull heading directly after us.

I am reading Richard Dana's Two Years Before the Mast in instalments, courtesy of DailyLit.

With pirates resurrected in the news in their historic character of murderous thieves, rather than the disneyfied romantic image of recent decades, it is striking to come across a reference to them in Dana's account of his voyage where an encounter with a strange and unmarked ship on the wide ocean represented a race for one's life.

We continued running large before the north-east trade winds for several days, until Monday, September 22d; when, upon coming on deck at seven bells in the morning, we found the other watch aloft throwing water upon the sails; and looking astern, we saw a small clipper-built brig with a black hull heading directly after us. We went to work immediately, and put all the canvas upon the brig which we could get upon her, rigging out oars for studding-sail yards; and continued wetting down the sails by buckets of water whipped up to the mast-head, until about nine o'clock, when there came on a drizzling rain. The vessel continued in pursuit, changing her course as we changed ours, to keep before the wind. The captain, who watched her with his glass, said that she was armed, and full of men, and showed no colors. We continued running dead before the wind, knowing that we sailed better so, and that clippers are fastest on the wind. We had also another advantage.

The wind was light, and we spread more canvas than she did, having royals and sky-sails fore and aft, and ten studding-sails; while she, being an hermaphrodite brig, had only a gaff topsail, aft. Early in the morning she was overhauling us a little, but after the rain came on and the wind grew lighter, we began to leave her astern. All hands remained on deck throughout the day, and we got our arms in order; but we were too few to have done anything with her, if she had proved to be what we feared. Fortunately there was no moon, and the night which followed was exceedingly dark, so that by putting out all the lights and altering our course four points, we hoped to get out of her reach. We had no light in the binnacle, but steered by the stars, and kept perfect silence through the night. At daybreak there was no sign of anything in the horizon, and we kept the vessel off to her course.