284 ILLUSTRATIONS OF THE BOTANY OF [ Solanee. 
find it almost impossible to ascertain what are the states of dryness or moisture of the 
atmosphere, what the nature of the winds, what the proportions between the richness of 
asoil and the dryness of the air, or even what the temperature during the different 
processes; for upon all these must depend both the growth of the plant and the nature 
of its secretions, as already pointed out in the article on the cultivation of Cotton, p. 88. 
But from the notices procurable from other sources, and especially the works of 
the illustrious Humboldt, it appears that though Tobacco be exported from very hot 
places in the Gulf of Mexico, it is only grown on elevated ground in the vicinity of 
Vera Cruz, Cumana, and Havannah, where, as will be seen in the accompanying notes,* 
a very slight elevation is sufficient to produce a modification of temperature, as well as 
a constant circulation and comparative dryness of the atmosphere; for as the lower 
strata become heated, they expand, and necessarily ascend; the capacity of air for 
moisture as for heat being in proportion to its rarefaction ; this, with coolness, will also 
produce dryness, which favours evaporation from the surface of leaves. Mr. Loudon 
has succinctly stated the requisites for obtaining good Tobacco. “< In hot, dry, and short 
summers, the Tobacco is small, but of delicate quality and fine flavour; in long moist 
and not very warm summers, it will grow large, but be without that fine flavour, which 
can only be given by abundance of clear sun-shine and free dry air. In the north of 
Germany, he adds, a good wine year, which depends on warmth and dryness, is always 
a good Tobacco year ;” and it may be inferred, that the combination of heat with 
moisture; 
* The island of Cuba, lying between N. lat. 23° 15’ and 19° 48’, only seventy miles in breadth, and every 
where pervaded by mountain ridges, must necessarily have its climate modified by these, as well as by its 
insular situation ; that is described as dry and warm, but more temperate and healthy than that of other 
W.I. islands. Moreover according to Humboldt, “ the influence of localities, of which the study is of so 
much importance to the cultivator, as the great breadth of the New Continent, the proximity of Canada, the 
winds which blow from the north, and other causes, give the equinoctial region of Mexico and the island of 
Cuba, a particular character. One would say, that in these regions the temperate zone, the zone of variable 
climates, increases towards the south, and passes the tropic of Cancer. In the environs of Havannah (lat. 23° 8”) 
the thermometer has been seen to descend to the freezing point, at the small elevation of 262 feet above the 
level of the ocean, and snow has fallen near Valladolid (lat. 19° 42’) at an absolute elevation of 6232 feet, 
while under the equator, this only takes place at double the elevation.” (Pol. Hist. of New Spain, IT. p. 362). 
In Mexico, the intendancy of Guadalaxara, which must participate in the causes affecting the climate of 
Valladolid, was celebrated for the abundance and excellent quality of the Tobacco which was produced. The 
cultivation is now restricted to the environs of Orizaba and Cordoba, and the partidos of Huatusco and Son- 
golica in the intendancy of Vera Cruz. (Humboldt, iii. p- 40). The towns are situated on the eastern decli- 
vity of the Pic d’Orizaba, and on the road to Xalapa, which, as elevated 7719 feet, enjoys a cool and agree- 
‘able climate ; that of Cordoba is warmer, but much cooler than that of Vera Cruz, 
have a freer circulation of air. 
_ Cumana is noted for the purity and healthiness of its climate, and the great heat incident to the situation 
being moderated by the sea breezes, “ Cumanacoa, fourteen leagues S.E. of Cumana, is a rich plain, 
by lofty mountains, and although only 630 feet above the sea, 
environs supply the province with Tobacco.”—Enc. Metrop. 
Bahia, also celebrated for its Tobacco, which was exported not only into Spain, but into Africa, and the 
South American States, has also any excessive heat of climate moderated by the sea breeze. 
and from its situation must 
surrounded 
possessed of a mild and even cold climate. Its 
