224 , 
ATMOSrnSBIC CHANGES. 
18'5° to 20°, which under this zone, and to the sensations of 
a traveller coming from the coasts, appears a great degree 
of coolness. I never perceived the temperature in the night 
at Curnana below 21°. The greatest heat is felt from 
noon to 3 o’clock, the thermometer keeping between 26° and 
27°. The maximum of the heat, about two hours after the 
passage of the sun over the meridian, was very regularly 
marked by a storm which murmured near. Large black and 
low clouds dissolved in rain, which came down in torrents : 
these rains lasted two or three hours, and lowered the 
thermometer five or six degrees. About five o’clock the 
rain entirely ceased, the sun reappeared a little before it set, 
and the hygrometer moved towards the point of dryness ; but 
at eight or nine we were again enveloped in a thick stratum 
of vapour. These different changes follow successively, we 
were assured, during whole months, and yet not a breath of 
wind is felt. Comparative experiments ' led us to believe 
that ill general the nights at Cumanaeoa are from two to 
three, and the days from four to five centesimal degrees 
cooler than at the port of Curnana. These differences are 
great ; and if, instead of meteorological instruments, we con- 
sulted only our own feelings, we should suppose they were 
still more considerable. 
The vegetation of the plain which surrounds the town is 
monotonous, but, owing to the extreme humidity of the air, 
remarkable for its freshness. It is chiefly characterized by 
an arborescent solanum, forty feet in height, the Urtica 
baccifera, and a new species of the genus Guettarda.* The 
ground is very fertile, and might be easily watered if 
trenches were cut from a great number of rivulets, the 
springs of which never dry up during the whole year. The 
most valuable production of the district is tobacco. Since 
the introduction of the faring in 1779, the cultivation of 
tobacco in the province of Curnana is nearly confined to the 
valley of Cumanaeoa ; as in Mexico it is permitted only in 
* These trees are surrounded by Galega pilosa, Stellaria rotundifolia, 
Aegiphila elata of Swartz, Sauvagesia erecta, Martinia perennis, and a 
great number of Rivinas. We find among the gramineous plants, in the 
savanna of Cumanaeoa, the Paspalus lenticularis, Panicum ascendens 
Pennisetum uniflorum, Gynerium saccharoides, Eleusine indie*, Ac. 
+ “ Estanco real de tabaco,” royal monopoly of tobacco. 
