Henri fired at the horse, which dropped instantly, hurling the astonished Camanchee upon the ground, where he lay for some time insensible.  In a few seconds pursued and pursuers entered the wood, where both had to advance with caution, in order to avoid being swept off by the overhanging branches of the trees.

Meanwhile the sultry heat of which Joe had formerly spoken increased considerably, and a rumbling noise, as if of distant thunder, was heard; but the flying hunters paid no attention to it, for the led horses gave them so much trouble, and retarded their flight so much, that the Indians were gradually and visibly gaining on them.

“We’ll ha’ to let the packs go,” said Joe, somewhat bitterly, as he looked over his shoulder.  “Our scalps’ll pay for’t, if we don’t.”

Henri uttered a peculiar and significant hiss between his teeth, as he said, “P’r’aps ve better stop and fight!”

Dick said nothing, being resolved to do exactly what Joe Blunt bid him; and Crusoe, for reasons best known to himself, also said nothing, but bounded along beside his master’s horse, casting an occasional glance upwards to catch any signal that might be given.

They had passed over a considerable space of ground, and were forcing their way at the imminent hazard of their necks through a densely-clothed part of the wood, when the sound above referred to increased, attracting the attention of both parties.  In a few seconds the air was filled with a steady and continuous rumbling sound, like the noise of a distant cataract.  Pursuers and fugitives drew rein instinctively, and came to a dead stand; while the rumbling increased to a roar, and evidently approached them rapidly, though as yet nothing to cause it could be seen, except that there was a dense, dark cloud overspreading the sky to the southward.  The air was oppressively still and hot.

“What can it be?” inquired Dick, looking at Joe, who was gazing with an expression of wonder, not unmixed with concern, at the southern sky.

“Dun’no’, boy.  I’ve bin more in the woods than in the clearin’ in my day, but I niver heerd the likes o’ that.”

“It am like t’ondre,” said Henri; “mais it nevair do stop.”

This was true.  The sound was similar to continuous, uninterrupted thunder.  On it came with a magnificent roar that shook the very earth, and revealed itself at last in the shape of a mighty whirlwind.  In a moment the distant woods bent before it, and fell like grass before the scythe.  It was a whirling hurricane, accompanied by a deluge of rain such as none of the party had ever before witnessed.  Steadily, fiercely, irresistibly it bore down upon them, while the crash of falling, snapping, and uprooting trees mingled with the dire artillery of that sweeping storm like the musketry on a battle-field.

“Follow me, lads!” shouted Joe, turning his horse and dashing at full speed towards a rocky eminence that offered shelter.  But shelter was not needed.  The storm was clearly defined.  Its limits were as distinctly marked by its Creator as if it had been a living intelligence sent forth to put a belt of desolation round the world; and, although the edge of devastation was not five hundred yards from the rock behind which the hunters were stationed, only a few drops of ice-cold rain fell upon them.