Now, it is surprising how much detail the trained eye of a sailor will grasp, even in the brief space of time occupied by a gleam of sheet-lightning; it is due in part, I think, though certainly not wholly, to what scientists describe as "persistency of vision," or the phenomenon which causes an image to remain imprinted upon the retina of the eye for a quite appreciable period after the object has vanished. But I am certain that there is more in it than that, though precisely what it may be I cannot tell; suffice it to say that I was able to answer unhesitatingly: "A brigantine, sir, of about two hundred tons, under all plain sail. Very low in the water, and a decidedly suspicious-looking customer." "Just so," answered Galway. "Exactly what I made her out to be. Have the goodness to step down and report the matter to Captain Vavassour, if you please." There was no need, however; for the Captain, who had been reading in his cabin, had heard voices, and had come up on deck to see what was the matter. Then ensued another brief but intensely exasperating period of waiting until another flash came and once more betrayed the stranger's whereabouts. It came at length, and revealed her still standing to the eastward, and so close under the land that, but for the momentary illumination of her sails by the lightning, she would undoubtedly have slipped past us unseen. "Ah, yes, there she is; I see her!" exclaimed the skipper. "Wait until we are abreast of her, and then tack, Mr Galway," he continued. "No doubt they can see us a great deal more distinctly than we can see them, and if we tack now, they will doubtless do the same, with the result that they will be both to windward and ahead of us. But if we wait until she gets fairly past us, it will be a point in our favour, because if she stands on we can gradually edge down upon her." "She seems to be moving through the water very fast, light as is the wind," remarked the first lieutenant. "Ten minutes ago she was broad on our weather-bow, while now she is almost abeam. I expect we shall find that she is quite as fast as ourselves." CHAPTER NINE. THE PIRATE BRIGANTINE. We watched the stranger as she was revealed at uncertain but decreasing intervals by the silent sheet-lightning, which was now flickering up all round the horizon, affording us momentary glimpses of the great lowering cloud-masses that overhung our mastheads as though ready to fall and crush us, the shining undulations of the swell, with the small overrunning ripples caused by the faint breathing of the breeze, the distant land, and the brigantine sliding furtively along within its shadow. When at length she had drawn to a bearing two points abaft our beam, the Captain gave the word to tack; and when, three minutes later, we were fairly round, the yards braced up, sheets hauled aft, and the frigate gathering way on the starboard tack, the stranger lay straight ahead of us.