Ancient Civilisations Founded on Irrigation.

Timaru Herald, Volume LXXVIII, Issue 11998, 21 February 1903, Page 1 (Supplement)

Ancient Civilisations Founded on Irrigation.

A great part of Australia is more or less arid. People think this a tremendous misfortune; but in the United States — which is completel}' arid over nearly onehalf of its great extent—they now speak of "the blessings of aridity"—and they have cause to. There is also the fac'J that all the notable civilisations of antiquity nourished in dry regions. It has puzzled the historian —says Mr W. E. Bmythe, the author of that most stimulating and instructive book, " The Conquest of Arid America"—to account for the fact that the glories of antiquity sprang from the heart of the desert. The fact itself is, of course, beyond' dispute. Egypt, Asia Minor, and Syria, with Palestine, " the land of milk and honey " ; Persia, Arabia, and the classic lands of Northern India, as well as the countries of the Carthaginians and the Moors, were arid regions. So also were the homes of the Incas in South America, and of the Aztecs and Toltecs in Mexico and the American South-West, the fame of whose vanished civilisations is reflected in. the pages of Prescott and Baldwin.

The accepted explanation of the choice of the arid land by the ancient races is that they sought security against savage enemies, both animal and human, which infested the forest. The theory is purely sentimental and quite inconsistent with the slight but conclusive evidences of their superior intelligence and courage which yet survive. The reasonable explanation is that the arid lands were chosen because they were infinitely better than the humid lands, and because they presented conditions much better suited io the industrial polity of the people and the an-e. In searching lor the clue of , this°niystery, Professor HiJgard, of the University of California—perhaps the greatest living authority on soils—has developed facts which tend to upset other accepted theories. It has long been conceded that certain arid districts are the richest spots on the surface of the globe. " The Valley, of the Ivil'e," for instance, is a phrase which is everywhere taken as a synonym of extraordinary fertility. The richness and dur-

ability of the Kile lands, which have supported for centuries an average population, of a little more than one and a-half persons to each acre of cultivated soil, has been ascribed to the fertilising quality of the annual deposit of river sediment. That the famous Nile does, indeed, leave a thin deposit of rich soil upon each sub-

sidence of its annual flood the California scientist, of course, does not deny. He

noves, however, that this layer of new

soil is only of the thickness of common cardboard—o.ie twenty-filth of an inch—and is equal to only about two good twohorse loads per acre. Three times as much stable manure is the usual dressing: for an acre. He tiuly observes that as the :-i:iiinejit is jneiely rich soil, thousands of luime'.s could readfy haul and spread such fertiliser upon their land, and would doubtless do so if they could thereby duplicate the phenomenal fertility of the Nile countiy. Re clinches Ids argument by showing that the neighbouring province of Fayoom, in the Libyan desert, shares the perpetual fertility of the Nile district, though irrigated only with the clear waters of Lake Mueris ; that the regular lands of the Deccan, in South-Central India, have

been phenomenally productive for thousands of years, and that the loess region, of China, drained by the head waters of the Yellow River, has been the granary of China for ages. Like the famous Egyptian provinces the lands leferred to in India and China are arid or serai-arid, and unlike the Nile Valley they have not been enriched by sedimentary deposits or fertilised by irrigation. Hence, Professor Hilgard, who has set out his views in detail in recent numbers of American magazines, reaches the somewhat sensational conclusion, ■that the extraordinary fertility which, by world-wide acknowledgement, marks the valley of the Kile, is a quality inherent in aridity itself. Soils, he points out, are formed from rocks by the physical and chemical agencies commonly comprehended ed in the term "weathering," which includes both their pulverisation and chemical decomposition by atmospheric action. The weathering process is accompanied by the formation "of new compounds out of the minerals originally composing the rock. Some of these, such as zeolites and clay, are insoluble in water, arid therefore remain in the soil, forming a reserve of plant food that may be drawn upon gradually by plants; while another portion, containing especially the compounds of the alkolis —■ potash and soda—are easily soluble in water. Where the rainfall is abundant, these soluble substances are currently carried into the country drainage, and through the rivers, into the ocean. As Mr Smythe puts it, the valuable ingredients of the soil which are soluble have been washed out of the land in humid regions by the rains of centuries. On the other hand, these elements have been accumulating in the arid soil of the west during the same centuries. They lie there now like an inexhaustible bank account on which the plant life of the future may draw at will, without danger of -protest. The process which created this rich soil goes on repeating itself—recreating the soil season after season. Having made more than one thousand, analyses of the soils of the arid and the humid regions of the United States —of the west and the east—he has demonstrated that the average arid soil is equal, to 1 lie monfc phenomenal soil of the cast, while the soil of (he avid west as a whole is beyond comparison with that of (ho humid east as a whole. Thus the conspicuous Messini; of ariditv - is ils remark-sble eil'ect on 1 lie "soil. The land which the casual traveller, speaking ! out of the splendid depths of his ignor-. ■ ante and prejudice, condemns as " worlh- : less." and Jit only "to hold the earth ; toj'-et.Ver," is in 7-e-di'y rich and durable b'.ynnd :he most favoured dHricts in tho '-.r.r.ud iY-»ions.

It is in 1 lie fa.v 'Mb:;! it com; cis the use, of iriiixatii.-.i'' that Mr !:'mylhe iiudfi the chief blessing of aridity.