568 Foreign Notices : — Africa. 



in the rainy season. These vegetable matters act on the sulphates con- 

 tained in the sea water, and by their action sulphuretted hydrogen is evolved, 

 to which in great part, beyond all doubt, the insalubrity of these shores is to be 

 attributed. The extent of sea over which this fatal cause predominates is 

 estimated at 40,000 square miles ; and it no doubt accounts for the facts 

 mentioned, but for which no reason was assigned, in the invaluable reports 

 lately published by government, and in which the dry igneous rocks of parts of 

 that dreadful coast appear equally fatal to health as the marshy and moist dis- 

 tricts. It also confirms what I have long been convinced of, that the dread 

 effects of the mangrove, sleeping under which is always considered to pro- 

 duce inevitable death, are caused, not by the tree itself or its exhalations, as is 

 the common belief, but by the local nature of its habitat, which is the saline 

 estuaries, just where the chemical causes above mentioned are the strongest in 

 their operation. 



Like so many other discoveries, this very important one has been owing to 

 collateral circumstances. The evolution of the gas, and the impregnation 

 of the water by it, are most fatal to the copper on ships' bottoms ; and the 

 investigation of this comparatively unimportant object of economy appears 

 to have led to the knowledge of the true cause of the enormous loss of life 

 which has attended all our operations on that coast. There is no question 

 that the subject ought to be, and will be, followed up ; as it can easily be 

 done by orders sent to the different foreign stations, to collect the waters 

 on those coasts which are well known to be the most insalubrious. I may 

 point to the Mozambique country, on the east coast of Africa, some parts of 

 which appear to be, by the effects on men and officers employed there, if 

 possible more fatal to human life than those of the western coast. In the west, 

 the whole coast of Guiana, from Cayenne and the Oyapoh to the mouth 

 of the Orinoco, should be examined ; and the Bay of Honduras, as well as 

 the coast of Vera Cruz, and the opposite coast of Acapulco ; and parts of 

 the sea opposite the rivers of St. Domingo, which, in the rainy season, convey 

 vast quantities of trees and other vegetable matter to the ocean. There 

 is no doubt that the same cause operates in many places, in fact, almost every 

 where, though with less intensity as you approach the arctic circle ; and that 

 the sea water is every where more or less affected by the influx of quantities of 

 vegetable matter brought down by the rivers at particular seasons, though hap- 

 pily in the temperate zone we are comparatively free from its noxious effects. 

 In the future researches of the learned professor we trust to be informed of the 

 effect of heat in producing these exhalations ; and, as successive observations 

 give the requisite data, we may find that the same quantity of vegetable 

 matter, or nearly so, in one latitude may be almost innoxious, whilst in 

 another it may produce the fatal effects unhappily found in the countries 

 recently examined. 



The antidote recommended to this fatal poison is chlorine, the effect of 

 which, as is well known, is to completely neutralise the sulphuretted hydrogen; 

 in the words of the professor, " they cannot coexist :" and orders have been 

 given to furnish the expedition lately sent to the rivers of Africa with 

 an abundant supply of this substance. I hope and trust it may be bene- 

 ficial, but it is extremely difficult to deal with an entirely infected atmo- 

 sphere, to which both men and officers must be exposed. It is probable, by 

 fumigating the lower parts of the vessels in which the men sleep, a great 

 deal of good may be done ; and that by breathing a comparatively pure atmo- 

 sphere during the period of repose, the constitution may be better fitted to with- 

 stand the fatal miasmata whilst exposed to them during the other parts of the 

 day. To those who have to sleep in marshy districts, where it is possible to effect 

 it, there is no question that huts should be resorted to and fire kept, as well 

 as the chlorine fumigation now recommended and furnished by government 

 to t!ie African expedition ; and that the South American method of sleeping 

 in hammocks suspended to trees, as high as possible from the ground, should 

 always, if possible, be adopted. 



