26 PHILOSOPHICAL TRANSACTIONS. [ANNO I78I. 



These three therefore are in the following proportion; harmattan 133 inches, 

 Whydah 64 inches, and Liverpool 36 inches. 



3. Salubrity forms a third peculiarity of the harmattan. Though this wind is 

 so very prejudicial to vegetable life, and occasions such disagreeable parching 

 effects on the human species, yet it is Highly conducive to health. Those 

 labouring under fluxes and intermitting fevers generally recover in an harmattan. 

 Those weakened by fevers, and sinking under evacuations for the cure of them, 

 particularly bleeding, which is often injudiciously repeated, have their lives 

 saved, and vigour restored, in spite of the doctor. It stops the progress- of 

 epidemics: the small-pox, remittent fevers, &c. not only disappear, but those 

 labouring under these diseases, when an harmattan comes on, are almost certain 

 of a speedy recovery. Infection appears not then to be easily communicated 

 even by art. In the year 1770 there were on board the Unity, at Whydah, 

 above 300 slaves; the small-pox broke out among them, and it was determined 

 to inoculate; those who were inoculated before the harmattan came on, got very 

 well through the disease. About 70 were inoculated a day or two after the har- 

 mattan set in; but not one of them had either sickness or eruption. It was 

 imagined, that the infection was effectually dispersed, and the ship clear of the 

 disorder; but in a very few weeks it began to appear among these 70. About 50 

 of them were inoculated the second time; the others had the disease in the 

 natural way: an harmattan came on, and they all recovered, except one girl, 

 who had an ugly ulcer on the inoculated part, and died some time afterwards of 

 a locked jaw. Mr. Norris dissents from Dr. Lind, who speaks of the harmattan 

 as " fatal and malignant; that its noxious vapours are destructive to blacks as 

 well as whites; and that the mortality which it occasions is in proportion to the 

 density and duration of the fog." The baneful effects here pointed out proceed 

 from the periodical rains which fall in March, April, &c. and which are ushered 

 in by the tornados, or strong gusts of wind from the n. e. and e. n. e. accom- 

 panied with violent thunder and lightning, and very heavy showers. The earth, 

 drenched by these showers and acted on with an intense solar heat as soon as 

 the storm is over, sends forth such noisome vapours as strike the nostrils with 

 a most offensive stench, and occasion bilious vomitings, fluxes, and putrid fevers. 

 Besides these vapours, which are annual, there appears to be a collection of still 

 more pestiferous matter, confined for a longer time, and issuing from the earth 

 after an interval of 5, 6, or 7 years. There may indeed be instances in which 

 the harmattan comes loaded with the effluvia of a putrid marsh; and if there are 

 any such situations, the nature of the wind may be so changed as to become 

 even noxious. 



It appears that, except a few rivers and some lakes, the country about and 





