They still had the little stern-wheel steamer that was filched—­I beg their pardon, captured from the Free State, and in her, with the loot on board, they must creep down the Congo again, almost to Stanley Pool, steaming by night only, hiding at the back of islands during the days, always avoiding observation.  And then they must strike across country due west, till they made the head-waters of the Ogowe, and so down to the sea, fighting a way through whatever tribes tried to impede them.  The French Customs would take their toll of the ivory, of course, but that could not be helped; but after that, a decent steamer again, and the sea, and home.  It was an appetizing prospect.

But castles in the clouds have been built before, and often it is the unexpected that sets them trundling; and in this case such an ordinary occurrence as a tornado stepped into the reckoning and split this sighed-for edifice of success and prosperity with all completeness.

There had been no tornado to clear the atmosphere for nine whole days, and the country was unendurable accordingly.  The air was stagnant with heat, and reeked with the lees of stale vegetation.  The sky overhead was full of lurid haze, which darkened the afternoon almost to a twilight, and in the texture of this haze, indicated rather than definitely seen, was a constant nicker of lightning.  It was the ordinary heat-lightning of the tropics, which is noiseless, but it somehow seemed to send out little throbs into the baking air, till, at times, to be alive was for a white man almost intolerable.

[Illustration:  THE LITTLE ARMY COULD ONLY MARCH IN SINGLE FILE.]

Under this discomfort, a predatory column was marching on from one captured village to another, whose possible store of ivory had so far not been gleaned.  The road was the ordinary African bush-path, intensely winding and only foot-sole wide; the little army, with Kettle at its head, could only march in single file, and Clay, who brought up the straggling rear, sweated and panted quite half a mile behind his leader.

Every one knew the tornado was approaching, and both the worn and haggard white men and the sweating, malodorous blacks hoped for it with equal intensity.  For be it known that the tropical tornado passes through the stale baked air at intervals, like some gigantic sieve, dredging out its surplus heat and impurities.  The which is a necessity of Nature; else even the black man could not endure in those regions.

And in due time, though it lingered most cruelly in its approach, the tornado burst upon them, coming with an insane volley of rain and wind and sound, that filled the forests with crashings, and sent the parched earth flying in vicious mud-spirts.  In a Northern country such a furious outburst would have filled people with alarm; but here, in the tropic wilderness, custom had robbed the tornado of its dignity; and no one was awed.  Indeed the blacks fairly basked in its violence, turning their glistening bodies luxuriously under the great ropes of rain.