" The voyage up the Chobe, and the Zambesi after the junction of those rivers, was prosperous but slow, in consequence of stoppages opposite villages.

The origin of coal, that combustible which is distributed over the earth in all latitudes, from the frozen regions of Greenland to Zambesi in the tropics, utilized by the Chinese from the remotest antiquity for the baking of pottery and porcelain, employed by the Greeks for working iron, and now the indispensable element of the largest as well of the smallest industries, is far from being sufficiently clear.

In those journeys (1853-56) his routes were from the Upper Zambesi to Loanda in Portuguese West Africa, and then from Loanda to the mouth of the Zambesi, nearly twelve thousand miles of travel.