ARTESIAN WELL. 



ARTESIAN WELL. 



67 



should not have any communication with the surface. The facts, and 

 the theoretical reasoning, published with respect to the well of Orenrlle, 

 so strikingly illustrate the philosophy of similar operations, that a 

 short account of it is subjoined. 



Numerous wells had been sunk in the neighbourhood of Paris, and 

 also, it may be added, near London, in which a supply of water was 

 obtained from the permeable sand beds situated immediately above the 

 chalk, and covered by the impermeable tertiary strata. At Orenelle, 

 however, it was known, by experiment, that the permeable strata of 

 the other parts of the basin were replaced by marls and clays, which 

 intercepted the passage of the water; and therefore M. Mulot, the 

 engineer of the well, supported by the theoretical reasoning, and by 

 the authority of Messrs. Arago and Walferdin, resolved to seek a 

 apply of water by boring through the chalk into the subcretaceous 

 strata, which were believed to form a continous basin under Paris. At 

 Elbomf and at Rouen the chalk had actually been traversed, and the 

 water had risen at the former locality to a height of 82 feet above the 

 surface of the ground, or 109 feet above the level of the sea. M. Mulot 

 thence concluded that as the surface of the ground at Orenelle was 

 about 104 feet above the level of the sea, and was nearer the inland 

 outcrop of the water-bearing subcretaceous strata, the water furnished 

 by them would there flow over the surface. Messrs. Arago and 

 Walferdin, in fact, found that the level of the lowest point of the valley 

 of the Seine, in its course above the lower greensand formations, was 

 situated at Luaigny, near Troyes, where the surface of the land was 

 nearly 300 feet above the level of the plain of Crenelle; and they 

 inferred from this fact that not only would the water overflow the 

 borehole, but that it would also rise to a very considerable height 

 above the ground. The great Artesian boring of Crenelle was com- 

 menced upon faith in this reasoning; and after eight years of inde- 

 fatigable labour, in spite of all the accidents of the undertaking, and 

 the sneers of the incredulous, the efforts of M. Mulot were crowned 

 with signal success. After traversing the series of beds described 

 below, a supply of water equal to about 800,000 gallons per diem 

 was obtained from a depth of 1802 feet from the surface, or from a 

 depth of about 1698 feet below the level of the sea ; and this water 

 rose to the level of 122 feet above the ground at Crenelle. 



Before this result had been obtained, M. Walferdin mode a fwrip* 

 of observations upon the increase of temperature observable in exca- 

 vations made in the neighbourhood of Paris ; and he there found that 

 the mean temperature of the surface being fil'34, the temperature 

 below the surface became constant at a depth of 94 feet below that 

 level, and that it there invariably marked 63'06. In the boring itself 

 the thermometer marked, in the chalk, at a depth of 1319 feet from 

 the surface, 76'3 ; and in the gault, at a depth of 1657 feet, it marked 

 79*-61 ; thus showing that in the distance of 1553 feet below the line 

 of constant temperature, the total increase of temperature was 26'5S, 

 or about 1'7 for every succeeding 100 feet. According to this law of 

 increase of temperature, the water at the depth of 1802 feet below the 

 surface ought to have risen with a temperature of 81'96 nearly ; and 

 as they are stated to rise actually at the temperature of 81'81, they 

 must be considered to confirm, in a very striking manner, the 

 theoretical reasoning of M. Walferdin. It may be added that the 

 waters thus obtained are remarkably pure and soft, and that they arc 

 used for the municipal service of Paris. The bore-hole appears, how- 

 ever, to be exposed to occasional stoppages by the rising of sand: 



The brilliant success of this boring at Paris brought Artesian wells 

 into fashion, and a number of works of the same description were 

 undertaken in various parts of Europe, within a very short period of 

 the completion of the Orenelle well. Amongst the most important 

 of these were the borings undertaken in the Rhenish provinces for 

 bringing to the surface the waters of the brine springs of that district, 

 BOOM of which even exceeded the depth of 2400 feet from the surface. 

 But no new phenomena of the subterranean strata were observed in 

 these cases ; nor was any doubt thrown upon the universal application 

 of the laws of underground waters observed to prevail under Paris, 

 till the result of some Artesian borings, in the neighbourhood of Tours, 

 showed that it was impossible, & priori, to state infallibly the con- 

 ditions which would prevail at great depths. M. Degoussee mentions 

 in his ' Guide du Sondeur,' Paris, 8vo, 1847, that he himself had exe- 

 cuted no less than sixteen deep borings in the De'partement de 1'Indre 

 et Loire, of which ten are in the town of Tours and six in its neigh- 

 bourhood, and presented an avenge depth of about 600 feet. Two of 

 these borings were, however, unsuccessful ; and it appears that the 

 conditions under which they occurred, with respect to the great water 

 courses of the district, were such that it became necessary to suppose 

 that the underground course of the waters was interrupted by means 

 of a fault, or of an upheaval. At Calais, the result* obtained by the 

 great Artesian well there sunk were even more striking than those 

 obtained near Tours ; for after having in this case passed through the 

 drift above the chalk, the chalk itoelf, and the whole of the subcre- 

 taeeous strata, the boring was continued m tkt traiuitvm rod*, until 

 it had attained a total depth from the surface of about 1160 feet. 

 It will be necessary hereafter to refer to this well, and to the abnormal 

 sUte of the geological formations under this district. 



Very shortly after the completion of the Artesian well of Orenelle 

 some operations of the same description were undertaken in England, 

 of which the wells at Chichester and at Southampton were perhaps the 



most important. The former well waa carried through the strata of 

 the great Hampshire tertiary basin, then through the chalk, chalk- 

 marl, and upper greensand, wherein it stopped at a depth of 1054 feet 

 from the surface of the ground. Very little water was obtained from 

 this boring ; and, indeed, the low temperature at which the water 

 stood in the well, led to the inference that the supply could not have 

 come from the lowest level thus attained. The Southampton well 

 was carried through the tertiary beds of the same Hampshire basin as 

 had been traversed at Chichester ; and in this case the total thickness 

 of the series was not less than 434 feet The boring was then carried 

 through the upper and lower chalks, which here presented a thickness 

 of 851 feet ; and was finally abandoned in the chalk-marl, at a total 

 depth from the surface of 1317 feet, without securing any valuable 

 supply of water. A great number of Artesian wells had in the mean- 

 time been sunk in the tertiary basins of both London and Hampshire, 

 and the drain, thug established upon the subterranean watercourses of 

 those formations was so great, that the waters which originally had 

 flown over the surface of the ground, were no longer able to reach 

 that height; and it became evident that the demand upon these 

 water-bearing strata was rapidly exceeding the supply. Under these 

 circumstances the Hompstead and Highgate Water Works Company 

 resolved to renew under London the attempt which had been abandoned 

 at Southampton ; and their advisers argued that, inasmuch as the 

 outcrop of the subcretaceous formations was continuous around the 

 margin of the cretaceous basin surrounding and underlying the London 

 tertiaries, excepting on the eastern border, those subcretaceous strata 

 would be found under London just as they had been actually found 

 at Paris. 



This reasoning proved to be correct so far as the chalk-marl, the 

 upper grecnsaud, and the gault were concerned ; but when those for- 

 mations had been traversed (to a depth of 11134 feet) the boring tools, 

 instead of entering upon the lower grcensand, which theoretically had 

 been expected, entered upon and traversed to a total depth of 1302 feet, 

 a series of marls, clays, and sandstones, which appear in all probability 

 to belong to the new red sandstone series : all the intermediate strata 

 being absent. 



The interruption in the series of the subterranean strata at Highgate 

 corresponded in so very marked a manner with the analogous inter- 

 ruption previously observed at Calais, that geologists were forced to 

 admit that their theoretical reasoning with respect to such subterranean 

 strata could only present a character of certainty in so far as it enabled 

 them to foretell what formations vxndd not be found in any place, whilst 

 it afforded no guarantee as to what \nuld be found. In other words, 

 the lesson derived from these two wells was, that the first attempts to 

 secure a supply of water by means of an Artesian boring to a deep- 

 seated, and hitherto untried, stratum were exposed to great dangers 

 and difficulties, with respect to which the ordinary hypothetical reason- 

 ing possessed no character of certainty. Subsequently, the result of 

 the Artesian boring, as it was commonly, but somewhat incorrectly 

 colled, at Harwich, added to the point of this lesson ; for after travers- 

 ing the tertiaries, the chalk, chalk-marl, upper greensand, and gault, the 

 boring tools came, as at Calais, upon the transition rocks of a very early 

 geological period, at a total depth of about 1200 feet from the surface. 

 This result was, perhaps, the more remarkable from the fact that a 

 successful boring had previously been made at Stowmarkc't, within a 

 comparatively speaking short distance from Harwich, in which the 

 lower greensand was found to occur in the position it might have 

 been expected to have occupied iu the ordinary geological order. 

 More latterly still a very successful Artesian boring has been executed 

 at Ostend, where a supply of water has been obtained, but only from 

 the lower tertiaries, without traversing the chalk, at a depth of about 

 658 feet from the surface of the ground. 



It would appear from these facts, and from the very remarkable 

 success which has attended the efforts of the French military engineers 

 to obtain water in the Desert of Sahara, that in all cases where the 

 continuity of the subterranean water-bearing stratum is known to 

 exist, Artesian wells may advantageously be resorted to, provided the 

 quantity of water taken from them be not very considerable. From 

 the experience obtained near Paris, Tours, and London, howevi-r, it 

 would appear that the supply so to be obtained is very limited ; and 

 whenever the demand sensibly approaches the subterranean supply, 

 the first effect produced is to lower the level of the water line, and thus 

 very frequently to destroy the true Artesian character of the wells. 

 In the neighbourhood of Tottenham, for instance, the water now 

 hardly rises to the surface of the ground in some wells where formerly 

 it overflowed. 



The operation of boring for Artesian wells is effected usually by 

 means of wrought-iron rods, of about 20 feet long each ; the upper 

 end of the first rod having a hook, by means of which it is suspended 

 to the lever communicating to the system the necessary percussive 

 motion, and the lower ends of all the rods bearing a lie-screw fitting 

 into the socket of the she-screw on the head of the lower ones. Below 

 the suspending hook there is an eye intended to receive a hand lever, 

 by means of which the workmen give, when required, a rotary motion. 

 In traversing soft materials, such as chalk, clay, fine sand, &c., a mere 

 rotary motion will suffice to ensure the descent of the boring tool 

 carried by the lowest rod; and this tool, it must be observed, is 

 modified so as to suit the various descriptions of soil. But in traversing 



