Engineering Wonders of the World
Volume I

THE ARTESIAN WELLS OF AUSTRALIA 313 DIAGRAMMATIC PRESENTATION OF AN IDEAL AND AN IMPERFECT ARTESIAN BASIN. that time—now ancient from an engineering standpoint—did the process go on, the boring tools being driven with successive blows, until, at the quite unexpectedly small depth of 140 feet, refreshing water sprang up like a small fountain above the surface, to the great delight of the believers and the doubters who stood around. The water thus won was an insig- nificant drop in the great wilderness of the west, but its great importance was at once recognized. It indicated the presence of a vast underground supply, which would at least cause numerous oases to flourish in the desert. And now as to these scientific inferences which led up to this modern counterpart of bringing water from the rock in the wilderness. What may be called an ideal artesian basin is rarely to be found in Nature, but for the sake of the principles involved basin may be described. We An ideal Artesian Basin. such an ideal must imagine a porous stratum, such as sand or gravel, shaped like a very thick basin, hav- ing a water-tight stratum—clay, for example —below it, and partly filled inside with similar impervious material. The basin-shaped por- ous stratum “ out-crops,” or rises to the sur- face of the earth, in the form of a thick ring, and the rain falling upon this ring will sink through the porous material, collecting at the lowest point, and gradually saturating the whole stratum up to the level of the surface of the ring. This water, seeking its own level, of course exerts an upward pressure against the impervious clay inside the basin. Where the difference between the levels is very great and the superincumbent clay is of small depth, the upward water pressure has in some cases been so intense that earthquake-like up- heavals of the latter have taken place. Now, if a hole be pierced through such an overlying stratum as we have supposed inside the basin, the water will rise through it, and even above it in the form of a fountain as soon as the level of the water standing in the porous material forming the basin becomes higher than the top of the hole. Such a hole in such a position is an artesian bore or well, and is so called because this system of obtaining underground water under pressure was first used in Europe in the prov- ince of Artois in France more than a century ago. In the old days, the springing up of a jet of refreshing water in parched lands was indeed a mystery, a special act of a benevo- lent Deity. Now practically all our beautiful mysteries have faded away, and prosaic scien- tific reasons have taken their place. We have described an ideal or perfect artesian basin, but most of those of the world, as far as they are known, are very imperfect, being either tilted so much at one end, or broken through at one or more sides, that there is a very considerable leakage, and the pressure is maintained only by the friction of the strata checking the water, or by some other obstruction to its progress. In settled countries, the geology of which is well known, the character of artesian areas is ascer- A vast Australian Basin.