The boats were now completely concealed from all possible observation, for we soon saw that the islets between which we were anchored consisted merely of mud-banks thickly overgrown with mangroves, and absolutely uninhabitable even by natives; for there did not appear to be an inch of ground upon either of the islets sufficiently solid to support even a reed hut, while the mangroves were tall enough and grew densely enough to hide the boats from all possible observation from the mainland.  The only question which now troubled us was whether the presence of the boats in the river had already been observed.  If the slavers had placed absolute confidence in the success of their plan to draw us away from the coast by means of the decoy schooner, they might not have troubled to keep a look-out; but if they were as cautious as such gentry usually are, and had left nothing to chance, it would be scarcely possible for the approach of the boats to have passed undetected.  This was the question to which the captain was now going to seek an answer.