252 Dependence of the Geographical JRelations of Countries 



so that, on account of the extreme evaporation carried on by the 

 forests of hot countries, the instrument is unavailable for the 

 purposes of measurement, since there the moisture considera- 

 bly exceeds the highest point of the scale. 



Many and often-repeated observations have proved, that the 

 quantity of watery vapours with which the atmosphere is preg- 

 nant, increases proportionally with the extent and preserva- 

 tion of forests on the plains ; as also that it is modified by the 

 nature of the plants which have a particular share in deter- 

 mining the influence of forests on the formation of atmosphe- 

 ric humidity. 



Comparisons between woody and woodless countries furnish 

 many arguments in support of these assertions, which are ap- 

 plicable even to individual countries, for example, to Spain, 

 France, &c. Accordingly, the province of Gallicia is indebted 

 to the forests for its numerous population, and for many things 

 in which it claims superiority over almost all the other pro- 

 vinces of Spain ; the province of Estremadura, again, owes 

 the want of agriculture and the barrenness of the soil to the 

 absence of forests ; the greater part of this latter province 

 and of that of Murcia presents a bleak, barren, and desolate 

 aspect, merely because the mountains have been stripped of 

 their forests. In the latter province, there is frequently no 

 fall of rain for eight or ten months ; and the prevalence of dry 

 sultry weather forbids agriculture, and checks the increase of 

 population. The woody province of Valencia, on the other 

 hand, enjoys a mild and agreeable climate ; its damp and pro- 

 ductive soil is even favourable to the growth of the nobler 

 products, such as vines and cotton-trees, rice and palm-trees, 

 and completely provides for all the necessaries of life. Many 

 other provinces, deprived of their forests, for example. Old 

 and New Castile, exhibit strong contrasts in comparison with 

 the woody provinces of Leon, Catalonia, &c., clearly proving, 

 that the mountain forests impart a moderate quantity of mois- 

 ture to the atmosphere, which preserves the soil from becom- 

 ing dry and useless, promotes the growth of plants, and is 

 favourable to the increase of population, as well as to the thriv- 

 ing condition of the products of agriculture and of other branches 

 of industry ; finally, it procures the means necessary for the 



