24 CAPTAIN TUCKEY’S NARRATIVE, 
which has about 4500 feet of elevation, but also the whole 
central ridge of hills down to 1400 feet are usually enveloped 
in clouds from 10 o’clock in the morning. This humidity 
clothes the hills with thick pasture grass, giving to the 
country a feature entirely unlooked for in so low a latitude 
and of so small an elevation above the sea. 
«‘ It is also this moist atmosphere that causes the mean 
temperature of the island to be so much less than that of 
Senegambia. According to Humboldt’s new scale of mean 
temperatures, the curve will intersect the latitude of St. 
Jago at 27° of the centigrade thermometer, (80° 7’ of Faren- 
heit,) which is probably the middle between the iso-ther- 
mometer of the island and of Senegambia, the latter being 
probably not less than 30° centig. (86° of Fahrenheit). On 
the 10th of April the temperature of the well m the valley of 
Trinidad was 25° centig. (76° Fahrenheit), the well being 
two or three fathoms deep, and the afflux of water con- 
siderable, as it supplies the whole town. It is probable 
that this is about the mean temperature of the well through- 
out the year, and that we shall not be far wrong in con- 
sidering it also as the iso-therm. of the lower parts of the 
island.* 
* On boad the ship in the bay at 2 o’clock in the afternoon, the thermometer 
was 70°, while in the town of Porto Praya it was at the same time 84°. 
