712 PHILOSOPHICAL TRANSACTIONS. [aNN0 1780. 



prevent it in future in the like climates. Previous to the journal, in order to 

 illustrate it, Dr. S. makes a few remarks on the situation of the island, the 

 country about it, its seasons, tlie manner and time in v\ hich the disorder appeared 

 and ceased, &c. 



The island St. Lewis, otherwise called Senegal, is situated in l6° n. lat. and 

 16° w. long. It is separated from the island of Soar on the east by the main 

 river, which, on account of the smallness of the creek by which it is formed, is 

 esteemed a part of the continent. It has the Atlantic Ocean on the west, from 

 which it is separated by a small neck of land, or rather sand, called Barbary 

 Point. This neck of land is in several places not above 5 or (3oO yards broad. 

 A branch of the river runs between it and the island itself, communicating with 

 the main river above and below the island. It is about a mile in length, 700 

 feet in breadth, and contains 5 or 600O black inhabitants. In the months of 

 August, September, and October, it is usually about 2 or 3 feet above the level 

 of the river at high water; but there are years in which the whole island is over- 

 flowed ; in the other months of the year it may be about 5 or 6 feet above its 

 level in the highest places. The continent and islands near it are as low, and in 

 many places much lower, being overflowed for the most part during the rainy 

 months; the latter are formed by creeks communicating with the main river, 

 and thickly beset with mangroves. The water of the river is fresh during the 

 rains, but very thick and troubled, the current being so rapid and strong as to 

 stop the flood-tide; but in the dry months the river water is salt, and no other 

 water is to be had, but sucii as is procured by digging a pit into the sand, more 

 or less deep according to the height of the ground, into which the water filtrates 

 from all sides, and gathers up to the level of the river. This water is brackish; 

 but as no better is to be had thereabouts, the garrison, as well as the inhabitants, 

 make use of it, except when the river is fresh. 



The year is commonly divided by the Europeans, as well as the inhabitants, 

 into two seasons; viz. the rainy antl dry; by others called the sickly and healthy 

 seasons. The rainy or sickly one generally begins about the middle of July, 

 and ends about the middle of October; during this time the wind is generally 

 between the points of east and south, the quarter from which the tornados come. 

 It has been observed, that the season is more or less unwholesome in proportion 

 to the greater or lesser quantity of rain that falls. A tornado is preceded by a 

 disagreeable closeness and weight in the air, which seems to be much hotter than 

 the thermometer shows it to be; and it is known to come on by the rising of 

 the clouds to the south-east, which by joining become darker, so as to make the 

 •iiorizon look quite black, accompanied with lightning and thunder at a distance. 

 The breeze dies away by degrees as the tornado advances, and an entire calm 

 succeeds; the air becomes yet darker; :niimals and birds retire and shelter them- 



