The hot rain beat down endlessly, vertically; occasionally the sun burst through like a hammer. The humidity mouldered books and mildewed clothes; by evening every smooth surface carried a film of dampness; one spent one’s nights in a dew of sweat, by morning the sheet was wringing. I am used to tropical heat, but the breathless heaviness of the Ogowe during the rains, imprisoned on three sides by the great walls of forest and on the fourth by the steaming breadth of the river, was inhuman.