448 ANTIQUITY OF IRRIGATION. 
up, check, and divert the course of natural currents, and de- 
liver them at points opposite to, or distant from, their original 
outlets; they often require extensive reservoirs to feed them, 
thus retaining through the year accumulations of water— 
which would otherwise run off, or evaporate in the dry sea- 
son—and thereby enlarging the evaporable surface of the 
country; and we have already seen that they interchange the 
flora and the fauna of provinces widely separated by nature. 
All these modes of action certainly influence climate and the 
character of terrestrial surface, though our means of observation 
are not yet perfected enough to enable us to appreciate and 
measure their effects. 
Antiquity of Irrigation. 
We know little of the history of the extinct civilizations 
which preceded the culture of the classic ages, and no nation 
has, in modern times, spontaneously emerged from barbarism, 
and created for itself the arts of social life.* The improve- 
richness of the soil seemed to have designed for the most abundant har- 
vests. In ground thus pervaded with moisture, or rendered cold, as the 
Tuscans express it, by the filtration of the canal-water, the vines and the 
mulberries, after having for a few years yielded fruit of a saltish taste, rot 
and perish. The wheat decays in the ground, or dies as soon as it sprouts. 
Winter crops are given up, and summer cultivation tried for a time ; but the 
increasing humidity, and the saline matter communicated to the earth— 
which affects the taste of all its products, even to the grasses, which the cat- 
tle refuse to touch—at last compel the husbandman to abandon his fields, and 
leave uncultivated a soil that no longer repays his labor.”—Tableau de lV Agri- 
culture Toscane, pp. 11, 12. 
* T ought perhaps to except the Mexicans and the Peruvians, whose arts 
and institutions are not yet shown to be historically connected with chose of 
any more ancient people. The lamentable destruction of so many memorials 
of these tribes, by the ignorance and bigotry of the so-called Christian bar- 
barians who conquered them, has left us much in the dark as to many points 
of their civilization ; but they seem to have reached that stage whee continued 
progress in knowledge and in power over nature is secure, and a few more cen- 
turies of independence might have brought them to originate for themselves 
most of the great inventions which the last four centuries have } estowed upon 
man, 
