"Ay, ay, sir," I replied, touching my hat; and five minutes later I was sitting in the main-topmast cross-trees, with the long barrel of the telescope steadied against the topmast-head, and my eye glued to the eye-piece.  From this elevation I commanded a complete, if distant, view of the low land about the river entrance, with its fringe of mangrove trees running away inland, the sand hummocks, sparsely clothed with coarse, reedy grass and trailing plants, and the endless line of the surf-beaten African beach.  Also through the skipper's powerful lenses I obtained a most excellent view of the strange schooner, from her trucks to her water-line, including such details as I could have discerned with the naked eye at a distance of about half a mile.  I saw, for example, that, as the look-out had already reported, she was a large schooner--I estimated her to be one hundred and eighty tons burthen at the least; I verified the statement that her hull was painted all black from the rail to the top of her copper; that she showed an enormous spread of canvas; and that she sat very low in the water.  But I noticed a few other peculiarities as well; I saw that her bowsprit was painted black, while her jib-booms were scraped and varnished; that her foremast, fore- topmast, and fore-topgallant and royal-mast were varnished, while the mast heads were painted black, and that the whole of the mainmast, from the cap down, was painted _white_, which was a peculiarity that ought to have been sufficient to identify her as far as one could see her.  And so it was; for the moment that I reported it the skipper hailed--