Great forests and jungles and canebrakes swept past them.  In those tangles of gnarled trees, matted vines, interlacing rank grasses, and clusters of towering plants, so dank with the odor of wet and decay that the air even up where the flyers were seemed charged with it, lurked many a monster reptile and ferocious beast.  Often the four boys saw the majestic form of a lion or the lumbering shape of an elephant as these animals were quenching their thirst at some open spot along a stream.  And once they caught a brief glimpse of a terrific combat between what seemed to be two enormous rhinos, which had met in a little glen in the midst of a cluster of mahogany trees.  How they would have liked to see the finish of this battle royal!  Indeed, they would have enjoyed nothing better than to land in some favored spot and do a little big-game hunting with their rifles!