424 DEAINESTG OF SWAMPS. 



fused modes of resisting or directing the flow of waters, wliicli 

 have been practiced from remote antiquity in the interior of all 

 civilized countries. Draining and irrigation are habitually re- 

 garded as pm-ely agricultural processes, kaviug httle or no rela- 

 tion 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. 



Superficial draining is a necessity in all lands newly reclaimed 

 from the forest. The face of the ground in the woods is never 

 so regularly inclined as to permit water to flow freely over it. 

 There are, even on the hillsides, small ridges and depressions, 

 partly belonging to the original distribution of the soil, and partly 

 occasioned by irregularities in the growth and deposit of vegeta- 

 ble matter. These, in the husbandry of nature, serve as dams 

 and reservoirs to collect a larger supply of moisture than the 

 spongy earth can at once imbibe. Besides this, the vegetable 

 mould is, even under the most favorable circumstances, slow in 

 parting with the humidity it has accumulated under the protec- 

 tion of the woods, and the infiltration from neighboring forests 

 contributes to keep the soil of small clearings too wet for the 

 advantageous cultivation of artificial crops. For these reasons, 

 surface draining must have commenced with agriculture itself, 

 and there is probably no cultivated district, one may almost say 

 no single field, which is not provided with artificial arrangements 

 for facilitating the escape of superficial water, and thus carrying 

 off moisture which, in the natural condition of the earth, would 

 have been imbibed by the soil. 



All these processes belong to the incipient civilization of the 

 ante-historical periods, but the construction of subterranean chan- 

 nels for the removal of infiltrated water marks ages and countries 

 distinguished by a great advance in agricultural theory and prac- 

 tice, a great accumulation of pecuniary capital, and a density of 

 population which creates a ready demand and a high price for aU 

 products of rural industry. Under-draining, too, would be most 

 advantageous in damp and cool cHmates, where evaporation is 

 slow, and upon soils where the natural inclination of surface does 

 not promote a very rapid flow of the surface-waters. All the 

 conditions required to make this mode of rural improvement, if 



