IRRIGATION. In warm climates, where at certain seasons there is no rain, artificial watering must be adopted. Hence it became one of the first supplementary arts practiced in agriculture among the ancients, especially in Egypt. The appliances were crude, and the manual labor connected with it excessive; but in those early days the common people were slaves, their labor costing their masters merely the coarse food eaten, and the scanty clothing supplied.' Modern intelligence has reduced irri gation to a science, wherever Europeans have penetrated, but in some Oriental countries nearly the same means are now employed as in .ancient times. In irrigating the soil, the stagna tion and evaporation of the water applied is to be guarded against. It would create as great an evil as drought. The circulation of the water is necessary. Hence, the more porous the soil, and especially the subsoil, the greater the vigor of the irrigated vegetation. Hence two principles have been established in irrigation. A sufficient supply of water during every period of the growth of the crop, and never to allow it to remain at rest on the land. In the cultivation of rice an exception is made. One of the objects of water here is to kill weeds. It is simply inundating the soil, and is called warping. Irri gation is the supplying of plants and the soil with water, either by showering, or by con ducting the water over the land by means of artificial channels. In the United States the irrigation of water meadows has been practiced in some of the Eastern States. In the rice grow ing regions of the South, flooding is practiced, and in cranberry cultivation the same means must be available to secure the best results. In California, Utah, and Colorado, extensive systems of irrigation, involving the outlay of large capital, is common, and with , the best results. In fact, in California, irrigation is con sidered essential in the reclamation of the swamp lands of the State, and that it would be of com paratively little use to reclaim from overflow the swamp-lands of the Sacramento or San Joaquin Valleys without providing at the same time an efficient system of canals and ditches for irri gating them during seasons of drought. The lowlands have an advantage in retaining their moisture to a later period in the season than the uplands; but experience shows that their pro ductiveness is materially affected by drought, and that no reclamation is perfect which does not include the means of irrigation. The Com mission appointed some years ago by the general government for the examination of certain lands and rivers in California with reference to irriga tion, in their report say, the first point in a sys tem of irrigation is to raise the surface of the water in the river to a level which will enable it to flow freely over the hiithest ground to be irri gated. This is usually none by a dam; but in the construction of dams, a great many mechani cal, hydrostatic, and hydraulic principles must be applied under a great variety of circum stances. In the Old World, it is said, it is diffi cult to find two dams resembling each other. The size, alignment, and construction of the main canals constitute another branch of hy draulic engineering. The quantity of ]and to be irrigated, the nature of the soil, the minimum rain-fall, the kind of cultivation to be applied, and other considerations must be embraced in the programme of construction. The subordin ate channels which are to convey the water down to the plow-furrows require the application of scientific principles. The following statement will show the methods which the commission considered practicable and suited to the peculiar features of the Great Valley. These methods are based on results of irrigation systems in the Old World. This account is taken from the works of San Joaquin and King's River Canal. The main canal has a slope of one foot per mile, the ground sloping at the rate of eight feet per mile. Water is not taken immediately from the main canals to the irrigated ground, but to the primary ditches, which follow the highest part of the ground and are about a mile apart. The section is partly in excavation, and partly in embankment. As a general rule water should not be taken from primary ditches, but through secondary ditches. Each secondary ditch irri gates the land between it and the next one below it, embracing about eighty acres. The land is subdivided, first, by plow-furrows, forty yards apart, parallel to the primary ditches. It is again divided by cross-furrows, called checks, fifty yards apart and parallel to the primary ditches. By closing the gate at the mid dle of the ditch, all its contents are dis charged into the ten furrows above, through little gates at the head of each. The first check furrow will arrest the flow and cause it to spread over the strip between it and the secondary ditch. When this is sufficiently irrigated, the check-furrow may be opened with the hoe, and the water will then overflow the second strip; and the process may be continued till the first forty acres are irrigated. Then close the small gates and open the gate in the secondary ditch, and in like manner irrigate the lower forty acres. As the ground slopes from the secondary ditches at the rate of eight feet per mile, the level of each check-furrow will be 2.7 inches below its prede cessor. There will then be an inequality of depth of water at different points of a strip between the two furrows, but in porous soils there is a compensation in the percolation of the water in the check-furrows to the land just below them. In impervious soils, or in irrigation for alfalfa, or permanent pastures, the furrows and check-furrows must be more numerous. The surplus water is caught in catch-drains for irri gating land still further down the system. The irrigation of ]ands should not be undertaken except under due consideration. Irrigation is costly. It is not a current annual account simply, but an outlay to start with, that must be made as a permanent investment. The annual outlay is also considerable, amounting often to five dollars per acre. When hand labor is scarce and high this must be taken into account. Sub terranean irrigation by means of drain pipes has been practiced in California. The plan has long been known in England, but in that moist climate is not recognized as of value. Warping, allowing the water to back over ]and, is used when there is tide water, and quickly produces results. In irrigation, sand and porous land receives the greatest benefit from irrigation; clay soils are least benefited, since they per colate water slowly, and one of the effects of irrigation is constantly to compact and harden the soil. Hence, cultivation should always fol low irrigation between waterings, as soon as the soil becomes dry enough. Indeed, this is one of the best known means of conserving the water irrigation rrigation by preventing undue evaporation, and in irrigation, the greater the descent and the quicker the flooding, the greater the benefit. It is also essential, that means be proyided to secure the escape of superabundant water quickly, once the soil is saturated, since, as before stated, once water has done its work, stagnation is injurious. The history of irrigation and its advantages have been summed up as follows: The art of producing large, crops by means of artificial supplies of water, has been practiced from remote ages in the warm countries of the world. It was used by the aborigines of America, by the Incas, the inhabitants of Mex ico, extensively practiced by the Egyptians, the Romans, and at the present day in France and Germany. The Hindoos make no attempt at cultivation without artificial irrigation. The rivers of Italy are made subservient to agricul tural wants wherever it is practicable. Arthur
Young gives an account of an hour's run of water through a gutter, near Turin, which produced, in 1778. 1,500 livres. The rent of irrigated lands in Italy is much larger than upon land not watered. Moses, in speaking to the Israelites in the wilderness, said : The land whither thou goest in to possess it, is not as the land of Egypt, whence ye came out, where thou sowedst thy seed, and wateredst with thy foot, as a garden of herbs. Here the lawgiver alludes to the machines that were used in Egypt, which they worked with their feet, for raising water. Virgil tells how to bring down the waters of a rivulet upon the sown corn, and when suffering from beat, to convey the vivifying liquid from the crown of the declivity, in chan nels, to the roots of the plants. Columella, Pliny, Cato, Varro, etc., all dwell upon the importance of irrigation. It is found profitable in England to irrigate plantations of willows and other semi-aquatic trees upon dry soils. The efficiency of irrigation is dependent upon many considerations; one of the principal is the nature of the subsoil. When it is a tenacious clay, the preparation consists in suitable under draining, that would be useless where the sub soil is sand or open gravel. Some waters are injurious. Certain salts of iron are known to be unfavorable to vegetation. Waters issuing from factories impregnated with animal and vegetable substances, such as the waters of distilleries, brew eries, slaughter-houses, etc., are highly fertilizing; others issuing from chemical establishments, calico printing factories, are injurious. Salt water in small quantities may be found useful upon certain plants, such as the grasses, aspara gus, etc., while they are positively injurious to such plants as rice. The salt marshes of France are known to produce a superior quality of mutton, which commands a high price, and is known in the French market under the name of pres sal B. Waters impregnated with carbonate and sulphate of lime are very fertilizing. In certain parts of Germany, a weak solution of sulphuric acid has been employed for irrigating grass lands with great advantage. Those which hold in suspension mud and other detritus, are highly useful, particularly on sandy soils; the fine mud settles in the pores, and gives consis tency, but any soil would be benefited by water holding mud in suspension, and that, of course, in proportion to the amount of organic and saline matter in the mud. Sir Humphrey Davy thought that the protection of grasses from frost during the winter season was of great impor tance, for a meadow irrigated in winter is pre served from sudden alternations, and, from the effect of the roots being thrown out of the ground by alternate freezings and thawings. The water immediately in contact with the roots of the grass is rarely below 40° Fahr. In the month of March, in a meadow near Hungerford, the air was, at seven o'clock, a. m., at 29°. The water was frozen above the grass, and the tem perature of the soil below the water in which the roots were growing was 43°. While the temperature is thus prevented from falling dur ing the winter, it is kept cool during the summer. Irrigation supposes water in motion; if it be allowed to stand and stagnate, its effects would destroy the objects sought to be accom plished. instead of fine grasses we would have a growth of carices, junci, and other coarse plants of no value. Sir John Sinclair says that the advantages of meadow irrigation are chiefly as follows: With the exception of warping, it is by far the easiest, cheapest, and most certain mode of improving poor land, particularly if it is of a dry and gravelly nature. Land once improved by irrigation, is put into a state of perpetual fertility, without any occasion for manure or trouble of weeding or any other material expense. It becomes so productive as to yield the largest bulk of hay, besides abun dance of the very best support for ewes and lambs in the spring, and for cows and other cattle in the autumn of every year. In favor able situations, it produces very early grass in the spring, when it is doubly valuable. Not only is the land thus rendered fertile without having any occasion for manure, but it produces large amounts of food for animals, which is con verted into manure, to be used on other lands, thus augmenting, in a compound proportion, that great source of fertility. The subject of irrigation is one of immense importance, in a dry, arid climate, such as characterizes portions of the western plains particularly. It is paramount, and may be employed throughout the continent with advantages greater than any other agricul tural application. It is an important art of itself, and one that requires special acquirements for its adaptation. The direct action of the fer tilizing constituents of water are not the only influences which that substance exerts upon our fields and growing crops. Its simple percolation through a soil has an important influence, by displacing gases and thus creating circula tion of air and bringing a fresh supply of ameli orating agents. It is not necessary in this article that we go into details of the various systems of doing work in the articles treated. These must be sought in Works written especi ally therefor, giving in detail the minutia. There are, however, many things to be it considered before entering upon the the con figuration of the land to know if t s adapted to .rrigai,loa, second, the water supply, to be sure that there is enough for every contingency. Then the nature of the soil, the character of the climate, and the nature of the subsoil must be taken into account. For instance, the greater the capacity of the soil for absorbing water, the longer it will retain it, so that a soil containing but a small amount of sand or gravel will not. need irrigation nearly so often as one composed: largely of sand; and yet the best results in irri gation, are reached, when water is abundant, io porous soils and subsoils, and for reasons hereto fore stated. To give some idea of the water required per acre, it may be stated that a stream, of water one inch wide and one inch deep flow ing four miles an hour will cover an acre one inch deep in twenty-four hours. Hence, thia would only suffice for seven acres to furnish an amount equal to the average annual rain fall which is fifty-two inches a year. In the irriga tion of gardens recourse is often had to the com mon watering cart. This may do as a make shift in times of drought, to keep special crops along until rain falls; no man would be foolish enough to depend upon this means in an arid climate. The only means here presented, where the water of natural streams can not be carried over the ground is by means of steam or wind power, and a system of underground pipes may thus be supplied, from a tank elevated twelve or fourteen feet, that will irrigate whatever the water supply will afford. Thus, with a tank holding 400 barrels, we hav6 had a full water supply for 1,100 hot bed sash, besides affording• all the water required at the house, barns, and wash-houses, no inconsiderable amount in a large market garden. A round tank, twelve feet and fifteen feet across will hold 15,000 gallons, and a square one sixteen feet across, and ten feet deep will contain nearly 20,000 gallons. Thus, such a tank if the water supply is sufficient to replenish it once a day, will furnish an inch a day over an acre of land. In times of extreme drought this supply will irrigate from five to seven. acres of land. Thus the land may be irrigated by surface pipes discharging over the beds, in jets or it may be carried in open channels but at a waste of water.