And, lastly, the noxious exhalations arising from the inaccessible forests and marshy swamps which abound in Africa, and from numerous animal and vegetable remains of the dry season, which cover the soil every where, are productive of putrid effluvia.  These rains, or rather periodical torrents of water, which annually visit the tropics, invariably continue for about four months of the year, and during the other eight it rarely happens that one single drop falls; in some instances, however, periodical showers have happened in the dry season, but the effects of these are scarcely perceptible on vegetation; the consequence is, that the surface of the earth forms an impervious stratum or crust, which shuts up all exhalation.

When the rains cease, and the heat of the sun absorbs the evaporations from the earth, which have been so long concealed during the dry season, a most offensive and disgusting effluvia is produced, which then fastens upon the human system, and begets diseases that in a short time shew their effects with dreadful violence; and no period is more to be guarded against than when the rains cease, for the intense heat completely impregnates the atmosphere with animalculae and corrupted matter.

The principal complaints which attack Europeans are, malignant nervous fevers, which prevail throughout the rainy season, but they are expelled by the winds which blow in the month of December; from hence these harmatans are considered healthy, but I have heard various opinions among medical men on this subject.  Dr. Ballard (now no more), whose long residence at Bance Island, and in Africa, and whose intimate acquaintance with the diseases of these climates, peculiarly qualified him to decide upon the fact, was of opinion, most decidedly, that the harmatan season was not the most healthy.

When this malignant fever takes place in all its virulence, its consequences are the most disastrous; the symptoms are violent and without gradation, and the blood is heated to an increased degree beyond what is experienced in Europe; the ninth day is generally decisive, and this is a crisis that requires the most vigilant attention and care over the patient.  I speak this from personal experience.  In consequence of the fatigues I underwent in the Rio Pongo, and other rivers, and having been for several days and nights exposed to an open sea, and to torrents of rain upon land, I was seized with this dreadful disorder, although I had enjoyed an uninterrupted state of good health before, and on my arrival at the colony of Sierra Leone was unable to support myself on shore; and had it not been for the kind attention and skilful prescriptions of Dr. Robson of that colony, with the friendly offices of Captain Brown, I should, in all probability, at this stage have finished my travels and existence together.  Dysenteries frequently follow this fever, which are of a very fatal tendency, and sometimes the flux is unattended by fever.  This disease is not uncommon