24 PHILOSOPHICAL TRANSACTIONS. [ANNO 1781. 



or 4 returns of it every season. It blows with a moderate force, not quite so 

 strong as the sea breeze, which every clay sets in during the fair season from the 

 w. w. s. w. and s. w.; but somewhat stronger than the land wind at night from 

 the n. and n. n. w. 



1. A fog or haze is one of the peculiarities which always accompanies the 

 harmattan. The gloom occasioned by this fog is so great, as sometimes to 

 make even near objects obscure. The English fort at Whydah stands about the 

 midway between the French and Portuguese forts, and not quite a quarter of a 

 mile from either, yet very often from it neither of the other forts can be dis- 

 covered. The sun, concealed the greatest part of the day, appears only for a 

 few hours about noon, and is then of a mild red, exciting no painful sensation 

 on the eye. The particles which constitute the fog are deposited on the grass, 

 the leaves of trees, and even on the skin of the negroes, so as to make them 

 appear whitish. They do not flow far over the surface of the sea: at 2 or 3 

 miles distance from the shore the fog is not so thick as on the beach; and at 4 

 or 5 leagues distance it is entirely lost, though the harmattan itself is plainly 

 felt for 10 or 12 leagues, and blows fresh enough to alter the course of 

 the current. 



2. Extreme dryness makes another extraordinary property of this wind. No 

 dew falls during the continuance of the harmattan; nor is there the least 

 appearance of moisture in the atmosphere. Vegetables of every kind are very 

 much injured, all tender plants, and most of the productions of the garden, are 

 destroved; the grass withers, and becomes dry like hay; vigorous ever-greens 

 likewise feel its pernicious influence; the branches of the lemon, orange, and 

 lime trees droop, the leaves become flaccid, wither, and, if the harmattan con- 

 tinues to blow for 10 or 12 days, are so parched as to be easily rubbed to dust 

 between the fingers: the fruit of these trees, deprived of its nourishment, and 

 stinted in its growth, only appears to ripen, for it becomes yellow and dry, 

 without acquiring half the usual size. The natives take this opportunity, of 

 the extreme dryness of the grass and young trees, to set fire to them, especially 

 near their roads, not only to keep the roads open to travellers, but to destroy 

 the shelter which long grass, and thickets of young trees, would afford to skulk- 

 ing parties of their enemies. A fire thus lighted flies with such rapidity as to 

 endanger those who travel: in that situation a common method of escape is, 

 on discovering a fire to windward, to set the grass on fire to leeward, and then 

 follow your own fire. There are other extraordinary effects produced by the 

 extreme dryness of the harmattan. The covers of books, even closely shut up 

 in a trunk, and lying among clothes, are bent as if they had been exposed to 

 the fire. Household furniture is also much damaged: the pannels of doors and 

 of wainscot split, and any veneered work flies to pieces. The joints of a well- 



