1849.] 



exercised lij Trees on Clhnaie. 



439 



the other side of Tumbez towards Payta, an entirely different set of 

 objects present themselves. The forests disappear, the soil is sandy, 

 and of vegetation there is scarcely a vestige. Here rain, so to speak, 

 is unknown ; when I was at Payta, according to the testimony of 

 the inhabitants, it had not rained for seventeen years. This want of 

 rain is common in all the countries which border on the desert of 

 Sechura, and extends as far as Lima. In these countries rain is as 

 seldom seen as are trees. 



Thus, in Choco, whose soil is covered with forests, it rains conti- 

 nually ; on the coast of Peru, the soil of which is sandy, devoid of 

 trees, and destitute of verdure, it never rains ; and this, as I have al- 

 ready said, under a climate precisely the same as to temperature, 

 whose exposure and distance from the mountains is very nearly the 

 same. Peru is not at a greater distance from the Andes of Assuay 

 than are the humid plains of Choco from the western Cordillera.* 



In the case of Maimato the evidence furnished by tfie rain guage 

 proved beyond a doubt that the diminution of the running water was 

 not owing to a diminished fall of rain, as it was found by the observa- 

 tions of the second year that a greater quantity of rain had fallen than 

 during the first ; nor do I imagine the diminution was solely owing 

 -iro the lands being deprived of the protection from the sun's rays 

 which the leaves and branches afford, but the lands being cleared the 

 fallen leaves and roots of the trees no longer existed to retard the flow 

 of the water which fell : while 3,000 inhabitants of an active flourish- 

 ing settlement engaged in the cultivation of the articles indispensable 

 to the existence and comfort of man Avould soon cause on the table 

 land of San Jorge the great change in the quantity of spring water 

 which is the result of high cultivation, or agricultural improvement of 

 a country. "While the face of a country is rough the rain water 

 remains long among its inequalities, slowly sinking into the earth to 

 feed the springs or slowly running away from the surface, as from 

 bogs and marshes, towards the rivers. The rivers hence have a 

 comparatively gradual and regular supply even when rain has not 

 fallen for a long time, but in a well drained and well cultivated 

 country the rain by a thousand channels finds its way to the brooks 

 and rivers, almost immediately, producing often dangerous floods or 

 inundations of the neighbouring low grounds. 



* Jameson's Edinburgh Phil. Joiu-nal, p. 85, vol. xxiv. 1838. 



