At Stanley Pool, about 1100 feet above sea level, fever of a pernicious form was prevalent. While ascending the Congo with the wind astern we were unusually exempted from ague. But descending the Upper Congo, facing the wind, we were smitten with most severe forms of it. While ascending the Aruwimi we seldom thought of African fever, but descending it in canoes, meeting the wind currents, and carried towards it by river-flow and paddle, we were speedily made aware that acclimatisation is slow. Therefore it is proved that from 0 to 5000 feet above the sea there is no immunity from fever and ague, that over forty miles of lake water between a camp and the other shore are no positive protection; that a thousand miles of river course may serve as a flue to convey malaria in a concentrated form; that if there is a thick screen of primeval forest, or a grove of plantains between the dwelling-place and a large clearing or open country there is only danger of the local malaria around the dwelling, which might be rendered harmless by the slightest attention to the system; but in the open country neither a house nor a tent are sufficient protection, since the air enters by the doors of the house, and under the flaps, and through the ventilators to poison the inmates. Hence we may infer that trees, tall shrubbery, a high wall or close screen interposed between the dwelling-place and the wind currents will mitigate their malarial influence, and the inmate will only be subjected to local exhalations. Emin Pasha informed me that he always took a mosquito curtain with him, as he believed that it was an excellent protector against miasmatic exhalations of the night. Question, might not a respirator attached to a veil, or face screen of muslin, assist in mitigating malarious effects when the traveller finds himself in open regions? Three companies of forty men each were sent in three different directions to follow the tracks leading from Bavikai. The first soon got entangled in the thick woods bordering the Ngaiyu, and had an engagement with the natives of Bavikai, who were temporarily encamped in the dark recesses, the second followed a path that ran E. by N., and soon met a large force of natives coming from three different villages. One of our men was wounded in the head with a poisoned arrow. The third was perplexed by a network of paths, and tried several of them, but all ended in plantations of plantains and thin bush of late growth, and in the search these men encountered savages well armed and prepared with poisoned darts. We were therefore compelled to recross the river to the south bank, to try again higher up, to avoid the trying labour of tunnelling through the forest. [Sidenote: 1888. Oct. 10. Hippo Broads.]