IRRIGATION. The improving of land by means of watei, is an object of importance throughout the greater par; of the globe In various countries it is effected by na ture on the great scale, occasionally or partially modified by human skill and labour. In others, nature applies this powerful mean of improvement in efforts more detached and confined. In sonic parts, irrigation, as a mode of im provement, is effected principally by the agency of man; and in all cases, this agency, skilfully applied, is more or less useful.
A just view of the fatal effects produced by destructive floolis, compared with those which arc the result of ju dicious irrigation, and of that sterility which is occasioned by excess or by want of water, compared with the fertile produce of lands properly irrigated, would set in a proper light the advantages resulting from this natural mode of improvement, by which water is turned to use, instead of being left to run to waste and ruin.
According to circumstances, it may be employed for meliorating soils of different characters, and for increasing the produce in many variegated forms in most of the popu lous districts of the globe. The tropical rivers convey to the plains over which they flow those annual and immense supplies of enriching deposit, which nourish the corn that sustains a considerable proportion of the population ; or they tend to form and to enrich those vast savannahs, which occur in that extensive portion of the earth. In the warm but more temperate climates, there arc considerable tracts of soil, which, if not irrigated, are almost wholly barren ; and water is also employed there, for the purpose of en riching soils already fertile. It is a cheap and powerful manure for various crops of great value to man ; and the use of it is extended, according to the views and circum stances of the husbandman, into the vineyard, the corn field, the garden, the orchard, or the meadow.
Instructed by nature, and improved by experience in the use of this element for meliorating the soil, mankind has i already felt that it is of great value and importance from the equator nearly to the 60th degree of north latitude, and from the same extending on a more limited scale pat tly into the southern temperate zone ! The periodical rains widna the tropics could not be sufficient, in that burning climate, for nourishing the crops necessary to support the i people, if nature itself had not employed them, and if art and labour were not also employed in fertilizing vast tracts of soil. Es en in the milder climates of Italy and France,
immense advantages are derived from the judicious appli cation of this mo le ef improvement ; and, though it may appear parrdoxic .i, it is perhaps more productive still in the climate of England, notwithstanding its high northern latitude, a•d the moisture of its climate.
The truth is, that irrigation, when conducted on the right plan, is generally either preceded or accompanied by drain ing, embanking, or both ; and that it has therefore a ten dency at one time to improve the soil and the climate also, while the element of water, instead of being destructive, is directed to purposes the most useful to mankind.
It is chiefly in this view, that a proper general idea may be formed of irrigation. The advantages of this mode of improvement are greatest in populous districts, where the produce of land is of superior value, and the labour neces sarily bestowed on it may be had at an inferior price ; but in all situations water is valuable, when it can be safely di rected to enrich the soil, and to improve and augment the produce. Every one admires that beautiful arrangement of nature, under which putrescent substances, instead of being useless or noxious, become valuable, by affording new supplies of nutriment for living vegetables, and of course for animals ; but water either is, or may become one of the most valuable means known for improving the soil in every climate, excepting that where the cold is long continued and severe.