While we were awaiting the formal condemnation of the _Dona Isabella_ by the Mixed Commission, and the trial of her crew upon the charge of piracy, Captain Harrison, our skipper, busily employed himself, as was his wont, in hunting up information relative to the movements, present and prospective, of the slavers upon the coast.  And this was not quite so difficult to do as might at first be imagined; for, Sierra Leone being the headquarters, so to speak, of the British Slave Squadron, the persons actually engaged in the slave-trade found that it paid them well to maintain agents there for the sole purpose of picking up every possible item of information relative to the movements and doings of that squadron.  For it not unfrequently happened that, to those behind the scenes, an apparently trivial and seemingly quite worthless bit of information, an imprudent word dropped by an unwary officer respecting one of our vessels, enabled the acute ones to calculate so closely that they often succeeded in making a dash into some river, shipping a cargo of slaves, and getting clear away to sea again only a few hours before our cruisers put in an appearance on the spot.  And in the same way our own officers, by frequenting, in disguise, the haunts of the slavers and their agents, very often succeeded in catching a hint that, carefully followed up, led to most important captures being made.  It was, indeed, through a hint so acquired that we had been put upon the track of the _Dona Isabella_.