Though much has been done in many parts of the globe, in order to attain the proper advantages to be derived from irrigation, it is probable that few of these in proportion have yet been secured. The rains which inundate the Nile, the Ganges, and other great rivers, do not convey the full benefits to the rich plains which they fertilize, unless by embankments the management and distribution of the water be secured, and the culture of the soil duly attended to The deadly swamp, which is occasioned by water per mitted to go to waste by stagnation, may be converted in many instances, by industry and skill, into fertile soil. Even the most barren mossy flats have often been convect ed into meadows by natural irrigation. But in how many instances is this neglected, where it might by art and la bour be done ? England furnishes the most alluring speci mens of what is possible artificially, by means of water, not only in the improvement of soils by irrigation, but in cre ating new soils by warping ; yet we cannot extend our views without becoming sensible, that though much has been done in this field of improvement, a very great deal more still remains to be accomplished.
The truth is, that if draining and embanking were con ducted on liberal principles, with a view to, and in connec tion with irrigation, there would be far more advantage resulting from their union, than can ever be secured by attending to them separately. It may also be remarked, that these arts, though greatly improved, are yet far from practical perfection. Errors equally frequent and gross are still committed in them all, and these have a tendency to bring unmerited reproach upon arts of great utility to man.
It is not an easy matter to convince mankind, how much is really within the power of„,human skill and industry. The first settlers in the American colonies would not have believed what improvement, even in the climate, was to follow the draining and cultivation of their lands after the forests disappeared. Many ages elapsed, before the peo ple of Egypt were capable of duly appreciating the full swell of the Nile, and of turning its enriching floods to most advantage. The treatment and cultivation of soils enriched by flooding, and the due application of industry and skill it) raising the most suitable crops, require time and patience; and can seldom or never he fully attained, unless the political state of a country be favourable to it-, improvement. In this view, irrigation fairly appears as a part of an extensive system of national economy, which ought to embrace the husbandry of every country to which this art can be of material use.
Immense additional supplies of grass have been raised in England within the present age by means of irrigation. These have contributed in a very large proportion to the support of live stock ; and of course they have added not only to the general produce and value of the soils on which this art was employed, but also to that stock of manure which has been turned, with great effect, to the purposes of arable husbandry. An increasing population has fur nished at once the labour necessary, and markets for the produce : and irrigation has thus, indirectly, but in a very considerable degree, increased the value and the produce of corn lands. This known and important fact ought to
recommend the continuance of a system fraught with so much advantage, and to lead to farther improvement in its principles and progress.
On the other hand, it cannot be denied that errors have been committed in respect of this art. It has been tried in situations where nature did not favour the success of it ; or it has been employed in order to force a produce for which there was not an adequate demand ; or it has been attempted to such an extent as exceeded the proper sup plies of labour within the district : and in all these and other similar cases, the failure has been most unjustly as cribed to the art itself, when in fact it arose from errors on the part of those who conducted it.
Notwithstanding the generally enriching qualities of the floods which are sent down by tropical rains, it requires both skill and attention to cultivate the soils to advantage, and to plant in every soil and situation the most suitable crops. A cold and moist climate also requires a similar portion of skill, in order to turn irrigation to most ac count ; which answers in Britain much better for grass than for corn. Without this requisite skill and attention, it is evident that no art whatever can prosper : errors, therefore, which proceed from this want, ought in no de gree to bring discredit on the art itself.
The art of irrigation, fully considered and improved by observation, in connection with that of draining and of em banking, has been so highly improved in some parts of the globe, as to approach towards a scientific character. Its features vary, indeed, so much, in different climates, as hardly to per mit us to view them in a proper light. We contemplate in succession, the new established system of irrigating for grass in England ; that of the south of France and of Lombardy for grass, vines, olives, mulberries, and other purposes ; and though much ingenuity and consider able diversity tppear, we hesitate not to pronounce the whole included in one art. But where nature takes the lead, and human agency is employed only to promote the utility of her operations, we hardly recognize the art of ir rigation : yet it is really of great importance, not only on the lesser, but the larger scale ; and the shepherd who properly directs the course of a mountain st•eamlet, or turns the collected waters of his drains, in order to prevent stagnation or waste, and of course to promote the health of his flock, at the same time directing these waters in such a manner as to fertilize barren spots of soil, and thus to furnish additional supplies of food, really belongs to the same class of artists, as those who by means of embank ment, or otherwise, direct to the most useful ends the vast inundations of tropical rivers. The features of this art of irrigation appear very different, but the art itself is the same.