112 EFFECTS OF FORESTS ON MOISTURE 



inference from the present desolate condition of the regions of the 

 Euphrates and Tigris, or of the Holy Land, as contrasted with their 

 amazing fertility in the olden days;'' and, "changes such as these 

 have nothing to do with changes of climate." But, with the mass of 

 testimonies which I have piled around me to effects which have 

 followed immediately on the destruction of forests, I cannot assent to 

 the sweeping statement I have quoted. It may be freely admitted 

 that devastations occasioned by war may be followed by drought, 

 without compromise to the allegation that the destruction of forests 

 may be followed by drought. The devastations of war may include the 

 destruction of forests, apd it so happens that facts are not awanting 

 illustrative of the devastations of war being followed by an opposite 

 effect, with results corresponding to what might be expected therefrom. 



When Humboldt visited South America he was led to consider 

 what could be the cause or occasion of a process of desiccation which 

 was brought under his notice. To quote from a statement by Boussin- 

 gault, which is cited by Mr Marsh : — " ' The rivers which rise within 

 the valley of the Aragua, having no outlet to the ocean, form, by 

 their union, the Lake of Tacarigua or Valencia, having a length of 

 about two leagues and a-half [or seven English miles]. 



" ' At the time of Humboldt's visit to the valley of the Aragua, the 

 inhabitants were struck by the gradual diminution which the lake 

 had been undergoing for thirty years. In fact, by comparing the 

 descriptions given by historians with its actual condition, even 

 making large allowance for exaggeration, it was easy to see that the 

 level was considerably depressed. The facts spoke for themselves. 

 Oviedo, who, toward the close of the sixteenth century, had often 

 traversed the valley of the Aragua, says positively that New Valencia 

 was founded, in 1555, at half a league from the Lake of Tacarigua ; 

 in 1800, Humboldt found this city 5,260 mfetres [or three and a-half 

 English miles] from the shore. 



" ' The aspect of the soil furnished new proofs. Many hillocks on 

 the plain retain the name of islands, which they more justly bore 

 when they were surrounded by water. The ground laid bare by the 

 retreat of the lake was converted into admirable plantations ; and 

 buildings erected near the lake shewed the sinking of the water from 

 year to year. In 1796, new islands made their appearance. A 

 fortress built in 1740 on the island of Cabrera, was now on a 

 peninsula ; and, finally, on two granitic islands, those of Cura and 

 Cabo Blanco, Humboldt observed among the shrubs, some mfetres 

 above the water, fine sand filled with helicites. 



