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In order, however, that the value of irrigation may not be misunderstood or overrated by the colonial
entire depth of the mass, would be to cover it with vegetable mould, in which the volatile principles would become condensed. The soil that served as a cover, would then be converted into a powerful manure. AVhcn the fermentation is carefully watched, and prudently managed, I do not hesitate to say that the loss of ammonia is inconsiderable. The fermentation, in such case, presents a character differing essentially from that which marks the rapid putrefaction that does not fail to develope itself when the proper precautions are neglected. As an example of a hasty and unfavourable fermentation, I may mention that which takes place in droppings of horse-dung. I have seen them when left untouched, and when not exposed to the contact of water, acquire, in a few days, a very intense degree of heat, and take fire. I have seen them thus become reduced to a mere earth. Such are not the results of the gradual decomposition of horse-dung.
"When the receptacle is emptied in which the slow fermentation has been going on, the upper layer is found in pretty much the same state as when it was brought there; the portion immediately beneath has undergone some change, a slight odour of ammonia being perceptible. In the inferior strata the change is great; the straw has lost its consistence, it is fibrous and easily crumbles. When taken from a still greater depth, the colour of the compost is darker. That nearest the bottom is quite black; its scent is that of hydro-sulphuric acid: we recognise in it sulphuret of iron; and doubtless these sulphuric products are the consequences of the decomposition of sulphates under the influence of organic matter. It is by this sign that I recognise the goodness of the compost for the farm. The presence of sulphurets, and of the hydrosulphate of ammonia, need not create alarm; for scarcely is the dung spread upon the soil, than these products transform themselves into sulphates, and soon emit that musky odour which is peculiar to those substances.
"Doubtless, the state in which such manure is found is owing to the manner in which it has been placed and preserved during the entire period of its change; the elements would have followed quite another course in their decomposition, if they had been left exposed to the open air. To be convinced of this, it is only necessary to notice the purely ammoniacal odour which is so strongly developed during summer in stables, where the urine of horses and cattle stagnates on the ground.
"It will be easily understood how unfavourable to the good preservation of manure must be the custom, common in certain countries, of turning it, as it were to air it, in order to hasten its decomposition. Thus treated, it does indeed decompose more speedily, but that result, the object of which I cannot exactly understand, is not attained except by the sacrifice of the quality of the compost; for it is^evident that its volatile principles evaporate the more easily, the more their points of contact with the air are multiplied."' — From Boussingault's Work on Economic Jiurale, ifyc.
agriculturist, it is necessary to state that, as applied to the soil, it is not a manure, but that it is instrumental in rendering the action of manure beneficial: per se, it does not enrich the soil with any marked element of productiveness, (unless the water contains some salts in solution,) but it serves powerfully to develope the richness the soil itself contains. "On a soil poor in mineral food, cultivated plants do not flourish, however abundantly water may be supplied to them." In dry climates, like those of Chili, Peru, Lower California, New South Wales, and Van Diemen's Land, its agency on a soil becomes precisely similar to that exercised in moist climates by a slacked lime dressing.
Both operations are only the means of effecting a further disintegration of particles, and a further decomposition of valuable salts and alkalies, which, without the assistance of such solvents, would remain inert in respect to the nutrition of plants: hence, however great and wonderful may appear its action on vegetation, water is, nevertheless, only what Liebig determined it to be, "a mediating member of all organic life."
In Australasia, numerous traces are seen of the escape of carbonic acid gas through fissures of the earth: in Van Diemen's Land, these are more frequent than in New South Wales; and in the upper country, more developed than in the lower. Of these traces, the most remarkable is that offered by dead trees, and by some long stripes of a stunted and sickly vegetation ranged in fines parallel to the axis of perturbation, and producing an effect similar to that observed by the writer in Hawaii (Sandwich Isles), and Sumbawa, where the escape of carbonic gas, by excluding oxygen from the soil, rendered the latter comparatively sterile. From this circumstance, the waters in both the colonies, particularly at their source, are impregnated with this acid, and are charged with many mineral salts. In many instances, passing through calcareous rocks, or such as contain calcareous matter, they carry with them the dissolved lime, and, on evaporation, incrust with it all vegetable or mineral substances which they meet in their courses. The chemical character which the waters of New South Wales and Van Diemen's Land thus possess, renders them doubly valuable in irrigation.
Its introduction in Australia is both practicable and easy, though more so in Van Diemen's Land than in New South Wales.
To restrain the extraordinary fall of rivers by damming up their courses, to make reservoirs, or to restore the old natural basins of lakes in the upper country; to bring the waters in their gradual descent to bear on the agricultural land, or to raise them by simple contrivances of windmills, pumps, or hydraulic belts, to the required level, still remain as means of irrigation to be adopted; the trouble and cost of which have been much exaggerated, but which have been most extensively accomplished by people of less energy, less industry, and less capital than the Australian settler possesses; subject also to trammels and restraints on the part of their unenlightened rulers, of which the Australian can scarcely form any idea. (South America.)
In New South Wales, the river Karua, and the tributaries of the Hunter, afford a most extensive range for the introduction of irrigation: the whole country of Cumberland may also be laid out in irrigated lands, by means of the Grose and WarrUgambia, Hawkesbury and Nepean rivers, and with the aid of cheap wooden aqueducts. The river Nepean for the county of Campden ; the Wollondilly, for Argyleshire; the river Cox, for the vale of Cly wd; and the Campbell and Macquarrie, for Bathurst; all offer most valuable water-courses for reclaiming or for increasing the productiveness of the comparatively . sterile lands. The lower portion of Gipps Land, sheltered, as it is, to the northward and westward by the dividing range, and watered by five fine rivers, may be rendered, by irrigation, a most flourishing portion of the colony.
In Van Diemen's Land, the central elevation, containing, at an average altitude of 3000 feet above the plains and valleys, five lakes constituting more than 200 square miles of superficial extent, and which by trifling embankments may be extended to double that area, appears to the traveller as if created for the special purpose of affording irrigation. In point of supply of water, and of the natural facility for regulating it, there is, perhaps, no situation equal to it in the world.
A wise legislation upon the right of appropriating and conducting the water through different properties, a general concurrence of efforts towards the extension of irrigation, and the bringing over of some few practical men from Chili or British India, to show the cheapest mode of effecting it, is all that is wanted: labour, which is becoming every day cheaper, will do the rest.
On its usefulness and necessity it is superfluous to expatiate. It will suffice to remind the colonial reader, that in Van Diemen's Land, Mr. Kermode reaped five tons of fine hay and twenty tons of potatoes from an acre, and this upon a soil which, before irrigation was applied to it, produced nothing; and that Mr. Jamieson raised the exhausted power of production in a soil, by one year of irrigation, from eighteen to twenty-five bushels per acre; and lastly, that in Sinaloa and Sonora, wheat gives a return of sixty fold; maize, of from 120 to 220; and this in an exceedingly dry climate, on a soil of which the mineral constituents are similar to the Australasian soils, and entirely through the effects of irrigation.*
• Hacienda <le Los Labores (Mexico). — I have not yet been able to recover from the surprise which my sojourn in the province of Sonora has occasioned me. Each step I take, presents me with some fresh cause for its renewal. My excursion to this farm has been a very agreeable one. In this corner of the Spanish American repub. lie, where my preconceived notions, derived from men and books, presented me only with images of wild Indians, I have found white men united in civilised communities, and animated with the active desire of progress and improvement in the career which independence has opened to them. I have found their intercourse most pleasant, their hospitality large as that of the Koran, and their inner, or mental life, wonderfully developed. In fact, when the short period of time and the limited means, or rather the total want of those means, which elsewhere facilitate, encourage, and promote amelioration, are considered, the people of Sonora may be said to have made gigantic strides in the path of improvement.
The hacienda of Los Labores, where I now am, is the finest among many farms I have visited in Spanish America, which constitutes the home of its proprietor. Every where else they cultivate their farms purely as a means of speculation or produce, — rent or gain being the only object of agriculture. They never visit them except when obliged to do so, and then, only make a brief stay. Here the owner, without losing sight either of produce or profit, finds, nevertheless, in the mere cultivation of the soil, the principal attraction of agriculture; he struck root in it like the trees of his garden; and, although severed as he is from all acquaintance with the valuable innovations which have affected this important branch of industry in Europe, he has, by his unwearied pains and his continual personal superintendence, more than quintupled the value of his farm during the thirteen years that he has been its proprietor.
This beautiful estate, lying twelve leagues north-east of the Pitic, and comprising an area of eight square leagues, extends partly along the flat of a valley, partly along the slopes of the mountains which enclose it. A third of the whole is under cultivation. The flat bottom of the valley, all of which is now under tillage, was formerly a forest of acacias, which have been destroyed by the axe. At present its excellent soil, tolerably well irrigated, and protected by impenetrable hedges, is covered with rich harvests, which surround, when gathered in, the farm-yard and the house of the proprietor.
The evening mists were falling when I arrived here yesterday, so that I could only form a partial idea of the scene; but this morning I was out of doors by day-break, and found my host on foot also. Full of activity and ardour, he sought to reanimate the labours of the farmyard, which the night had suspended. His example found but few imitators, and his zeal was little responded to. The denizens of the