clay, into porous beds of the Plastic-clay formation, or into the Chalk.*

Important treatises upon the subject of Artesian Wells have lately been published by M. Héricart de Thury and M. Arago in France, and by M. Von Bruckmann in Germany.†

* One of the first Artesian wells near London was that of Norland House on the N. W. of Holland House, made in 1794, and described in Phil. Trans. London, 1797. The water of this well was derived from sandy strata of the plastic clay formation, but so much obstruction by sand attends the admis. sion of water to the pipes from this formation, that it is now generally found more convenient to pass lower through these sandy strata, and obtain water from the subjacent chalk. Examples of wells that rise to the surface of the lowest tract of land on the W. of London may be seen in the Artesian fountain in front of the Episcopal palace at Fulham, and in the garden of the Horticultural Society. Many such fountains have been made in the Town of Brentford, from which the water rises to the height of a few fect above the surface.

This height is found to diminish as the number of perpetually flowing fountains increases; and a general application of them would discharge the subjacent water so much more rapidly than it arrives through the interstices of the chalk, that fountains of this kind when numerous would cease to overflow, although the water within them would rise and maintain its level nearly at the surface of the land.

The Section, Pl. 68 is intended to explain the cause of the rise of water in Artesian Wells in the Basin of London, from permeable strata in the Plastic-clay formation, and subjacent Chalk. The water in all these strata is derived from the rain, which falls on those portions of their surface that are not covered by the London Clay, and is upheld by clay beds of the Gault, beneath the Chalk and Fire-stone. Thus admitted and sustained, it accumulates in the joints and crevices of these strata to the line A. B. at which it overflows by springs, in valleys, such as that represented in our section under C. Below this line, all the permeable strata must be permanently filled with a subterranean sheet of water, except where faults and other disturbing causes afford local sources of relief. Where these reliefs do not interfere, the horizontal line A, B, represents the level to which water would rise by hydrostatic pressure, in any perforations through the London Clay, either into sandy beds of the Plastic-clay formation, or into the Chalk; such as those represented at D. E. F. G. H. I. If the Perforation be made at G. or H. where the surface of the country is below the line A. B. the water will rise in a perpetually flowing Artesian fountain, as it does in the valley of the Thames between Brentford and London.

† See Héricart de Thury's Considerations sur la cause du Jaillissement des Eaux des puits forés, 1829.

VOL. I.-36

It appears that there are extensive districts in various parts of Europe, where, under certain conditions of geological structure, and at certain levels, artificial fountains will rise to the surface of strata which throw out no natural springs,*

*

Notices scientifiques par M. Arago. Annuaire, pour l'An. 1835. Von Bruckmann über Artesische Brunnen. Heilbronn am Neckar, 1833. The Diagrams in Pl. 69. Figs. 1 and 2. are constructed to illustrate the causes of the rise of water in natural, or artificial springs, within basinshaped strata that are intersected by the side of Valleys, or traversed by Faults.

Supposing a Basin (Pl. 69 Fig. 1.) composed of Permeable strata, E. F. G. alternating with impermeable strata, H. I. K. L. to have the margin of all these strata continuous in all directions at one uniformly horizontal level, A, B, the water which falls in rain upon the extremities of the strata E, F, G, would accumulate within them, and fill all their interstices with water up to the line A, B; and if a Pipe were passed down through the upper, into either of the lower strata, at any point within the circumference of this basin, the water would rise within it to the horizontal line A, B, which represents the general level of the margin of the Basin. A disposition so regular never exists in nature, the extremities or outcrops of each stratum are usually at different levels, (Fig. 1, a. c. e. g.) In such cases the line a. b. represents the water level within the stratum G; below this line, water would be permanently present in G; it could never rise above it, being relieved by springs that would overflow at a. The line c. d. represents the level above which the water could never rise in the stratum F; and the line e, f, represents the highest water level within the stratum E. The discharge of all rain-waters that percolated the strata, E, F, G, thus being effected by overflowing at

e. c. a.

If common wells were perforated from the surface, i. k. l. into the strata G. F. E, the water would rise within them only to the horizontal lines a b, e d, e f.

The upper porous stratum C, also, would be permanently loaded with water below the horizontal line, g, h, and permanently dry above it.

The theoretical section, Pl. 69. fig. 2. represents a portion of a basin intersected by the fault H, L, filled with matter impermeable to water. Supposing the lower extremities of the inclined and permeable strata N, O, P, Q, R, to be intersected by the fault or dike H, L, the rain-water which enters the uncovered portion of these strata between the impermeable clay beds, A, B, C, D, E, would accumulate in the permeable strata up to the horizontal lines, AA", BB", CC", DD", EE". If an Artesian well was perforated into each of these strata to A', B', C', D', E', through the clay beds A, B, C, D, E, the water from these beds would rise within a pipe ascending from the perforations of the levels A", B", C", D", E".

and will afford abundant supplies of water for agricultural and domestic purposes and sometimes even for moving machinery. The quantity of water thus obtained in Artois is often sufficient to turn the wheels of Corn-mills.

In the Tertiary basin of Perpignan and the chalk of Tours, there are almost subterranean rivers having enormous upward pressure. The Water of an Artesian well in Roussillon rises from 30 to 50 feet above the surface. At Perpignan and Tours, M. Arago states that the water rushes up with so much force, that a Cannon-ball placed in the Pipe of an Artesian well is violently ejected by the ascending stream.

In some places application has been made to economical purposes, of the higher temperature of the water rising from great depths. In Wurtemberg Von Bruckmann has applied the warm water of Artesian wells to heat a paper manufactory at Heilbronn, and to prevent the freezing of common water around his mill wheels. The same practice is also adopted in Alsace, and at Constadt near Stuttgard. It has even been proposed to apply the heat of ascending springs to the warming of green houses. Artesian wells

These theoretical Results can never occur to the extent here represented, in consequence of the intersections of the strata by valleys of Denudation, the irregular interposition of Faults, and the varying condition of the matter composing Dikes.

If a valley were excavated in the stratum M below A", the water of this stratum would overflow into the bottom of this valley, and would never rise on the side of the fault so high as the level H.

Wherever the contact of the Dike H, L, with the strata M, N, O, P, Q, R, that are intersected by it, is imperfect, an issue is formed, through which the water from these inclined strata will be discharged at the surface by a natural Artesian well; hence a series of Artesian springs will mark the line of contact of the Dike with the fractured edges of the strata from which the water rises, and the level of the water within these strata will be always approximating to that of the springs at H; but as the permeability of Dikes varies in different parts of their course, their effect in sustaining water within the strata adjacent to them, must be irregular, and the water line within these strata will vary according to circumstances, between the highest possible levels, A, B, C, D, E, and the lowest possible level H.

have long been used in Italy, in the duchy of Modena; they have also been successfully applied in Holland, China,* and N. America. By means of similar wells, it is probable that water may be raised to the surface of many parts of the sandy deserts of Africa and Asia, and it has been in contemplation to construct a series of these wells along the main road which crosses the Isthmus of Suez.

I have felt it important thus to enter into the history of Artesian Wells, because their more frequent adoption will add to the facilities of supplying fresh Water in many regions of the Earth, particularly in low and level districts, where this prime necessary of Life is inaccessible by any other means; and because the theory of their mode of operation explains one of the most important and most common contrivances in the subterraneous economy of the Globe, for the production of natural springs.

By these compound results of the original disposition of the strata and their subsequent disturbances, the entire Crust of the Earth has become one grand and connected Appa

* An economical and casy method of sinking Artesian Wells and boring for coal, &c., has recently been practised near Saarbrück, by M. Sellow. Instead of the tardy and costly process of boring with a number of Iron Rods screwed to each other, one heavy Bar of cast Iron about six feet long and four inches in diameter, armed at its lower end with a cutting Chisel, and surrounded by a hollow chamber, to receive through valves, and bring up the detritus of the perforated stratum, is suspended from the end of a strong rope, which passes over a wheel or pulley fixed above the spot in which the hole is made. As this rope is raised up and down over the wheel, its tortion gives to the Bar of Iron a circular motion, sufficient to vary the place of the cutting Chisel at each descent,

When the chamber is full, the whole apparatus is raised quickly to the surface to be unloaded, and is again let down by the action of the same wheel. This process has been long practised in China, from whence the report of its use has been brought to Europe. The Chinese are said to have bored in this manner to the depth of 1000 feet. M. Sellow has with this instrument lately made perforations 18 inches in diameter, and several hundred feet deep, for the purpose of ventilating coal mines at Saarbrück. The general substitution of this method for the costly process of boring with rods of iron, may be of much public importance, especially where water can only be obtained from great depths.

ratus of Hydraulic Machinery, co-operating incessantly with the Sea and with the Atmosphere, to dispense unfailing supplies of fresh Water over the habitable surface of the Land.*

Among the incidental advantages arising to Man from the introduction of Faults and Dislocations of the strata, into the system of curious arrangements that pervade the subterranean economy of the Globe, we may farther include the circumstance that these fractures are the most frequent channels of issue to mineral and thermal waters, whose medicinal virtues alleviate many of the diseases of the Human Frame.t

"Thus in the whole machinery of springs and Rivers, and the apparatus that is kept in action for their duration, through the instrumentality of a system of curiously constructed hills and valleys, receiving their supply occasionally from the rains of heaven, and treasuring it up in their everlasting storehouses to be dispensed perpetually by thousands of never-failing fountains, we see a provision not less striking, than it is important. So also in the adjustment of the relative quantities of Sea and Land, in such due proportions as to supply the earth by constant evaporation, without diminishing the waters of the ocean; and in the appointment of the Atmosphere to be the vehicle of this wonderful and unceasing circulation; in thus separating these waters from their native salt, (which though of the highest utility to preserve the purity of the sea, renders them unfit for the

The causes of intermitting Springs, and ebbing, and flowing wells, and many minor irregularities in the Hydraulic Action of natural vents of water, depend on local Accidents, such as the interposition of Siphons, Cavities, &c., which are scarcely of sufficient importance to be noticed, in the general view we are here taking of the Causes of the Origin of Springs. † Dr. Daubeny has shown that a large proportion of the thermal springs with which we are acquainted, arise through fractures situated on the great Hines of dislocation of the strata. See Daubeny on Thermal Springs, Edin. Phil. Jour. April, 1832, p. 49.

Professor Hoffman has given examples of these fractures in the axis of valleys of elevation, through which chalybeate waters rise at Pyrmont, and in other valleys of Westphalia. See Pl. 67, fig. 2.