The two staples of commerce are now represented by palm-oil, which can be produced in quantities over the lowlands upon the whole river delta, and along the banks from the mouth to Boma, a distance of at least fifty direct miles. The second, and the more important, is the arachis, or ground-nut, which flourishes throughout the highlands of the interior, and which, at the time of my visit, was beginning to pay. As the experience of some thirty years on different parts of the West Coast has proved, both these articles are highly adapted to the peculiarities of the negro cultivator; they require little labour, and they command a ready, a regular, and a constant sale. When time shall be ripe for a bonâ fide emigration, the position of Boma, at the head of the delta, a charming station, with healthy air and delicious climate, points it out as the head- quarters. Houses can be built for nominal sums, the neighbouring hills offer a sanatorium, and due attention to diet and clothing will secure the white man from the inevitable sufferings that result from living near the lower course. With respect to the exploration of the upper stream, these pages, compared with the records of the "First Congo Expedition," will show the many changes which time has brought with it, and will suggest the steps most likely to forward the traveller's views. At some period to come explorers will follow the line chosen by the unfortunate Tuckey; but the effects of the slave-trade must have passed away before that march can be made without much obstruction. When Lieutenant Grandy did me the honour of asking my advice, I suggested that he might avoid great delay and excessive outlay by "turning" the obstacle and by engaging "Cabindas" instead of Sierra Leone men. At the Royal Geographical Society (Dec. 14th, 1874) he thus recorded his decision: "For the guidance of future travellers in the Congo country, I would suggest that all the carriers be engaged at Sierra Leone, where any number can be obtained for 1s. 3d. a day. From my experience of them I can safely say they will be found to answer every requirement, and the employment of them would render an expedition entirely independent of the natives, who, by their cowardice and constant desertion, entailed upon us such heavy expenses and serious delays. My conviction, after nearly four years of travel upon the West African coast, is this: if Sierra Leone men be used, they must be mixed with Cabindas and with Congoese "carregadores," registered in presence of the Portuguese authorities at S. Paulo de Loanda. I conclude with the hope that the great Nzadi, one of the noblest, and still the least known of the four principal African arteries, will no longer be permitted to flow through the White Blot, a region unexplored and blank to geography as at the time of its creation, and that my labours may contribute something, however small, to clear the way for the more fortunate explorer.