360 
SUPERFICIAL DRAINING. 
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 oft', 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 observa¬ 
tion are not yet perfected enough to enable us to appreciate 
and measure their effects. 
Climatic and Geographical Effects of Surf ace and 
Underground Draining. 
I have commenced this chapter with a description of the 
dikes and other hydraulic works of the Netlierland engineers, 
because the geographical results of such operations are more 
obvious and more easily measured, though certainly not more 
important, than those of the older and more widely diffused 
inodes of resisting or directing the flow of waters, which have 
been practised from remote antiquity in the interior of all 
civilized countries. Draining and irrigation are habitually 
regarded as purely agricultural processes, having little or no 
relation to technical geography; but we shall find that they 
exert a powerful influence on soil, climate, and animal and 
vegetable life, and may, therefore, justly claim to be regarded 
as geographical elements. 
Surface and Under-draining and their Effects. 
Superficial draining is a necessity in all lands newly re¬ 
claimed from the forest. The face of the ground in the woods 
—which affects the taste of all its products, even to the grasses, which the 
cattle 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 VAgriculture Toscane , pp. 11, 12. 
