The League of the Leopard by Harold Bindloss

The region which lies behind the West African coast is not a pleasant one to traverse, and bad fortune seemed to attend Maxwell's expedition from the time it marched out of the seaboard settlement, where he had had trouble with certain French officials, as well as with the black head man from whom he hired his carriers. All of this Dane remembered when he halted, one burning afternoon, shoulder-deep in the tall grass of a swamp, worn out in body and perplexed in mind. Few Europeans are capable of much exertion in that country, especially during the hottest part of the afternoon; but the hammock boys were too weary to drag their burdens farther, and there was urgent need for haste. Dane accordingly had taxed his strength to the utmost during the last few hours. The tall grass stems were almost too hot to touch, and foul mire bubbled about their roots.

At least a league of it, through which, slashed by saw-edged blades and stabbed by broken stalks, the expedition must force its way, stretched toward an inland ridge of higher ground that rose from the morass. Beyond this, in turn, flat-topped hills dimmed by a yellow heat haze cut the horizon.