1842.] 



THE CIA^IL ENGINEER AND ARCHITECT'S JOURNAL. 



241 



are now in process of being sunk for the purpose of a coal-pit. They have 

 encountered a stratum of sand lying between the magnesian limestone and 

 the coal formation, abounding with water to an extraordinary degree. For 

 some mouths past, and up to the present moment, more than 10,000 gallons 

 per minute, or 14,000,000 per 24 hours, have been pumped from the stratum 

 of sand crossing these two shafts. 



Here, then, surely we have an instance which proves the practicability of 

 obtaining, within a small space, a much greater quantity of water than is 

 sought for, or calculated upon, from the proposed shafts in the chalk. 



It is probable that some may be found to urge that, even here, the cases 

 are not absolutely parallel, the water in the one instance being drawn from 

 sand, and in the other from chalk ; but I would ask when we connect this 

 case of quantity with those already n)entii)nc<i as actually existing in the 

 ciialk, (for example, at Brighton,) can any reasonable doubt be entertained 

 that a supply, up to the amount of 10,000 gallons per minute, or more, may 

 may be obtained from the chalk by the adoption of the means I have 

 proposed ? 



Having, I believe without-prejudice, most carefully weighed these and all 

 other facts wliich have come before me relative to this matter, I have mil// 

 to add, that I am perfectly convinced of t he feasibility of ttie proposed plan, 

 as far as regards quantity. 



.4nd now I beg to relinquish this part of the subject, and proceed to 

 another, which will, doubtless, form one of the chief features in the oppo- 

 sition which you will encounter in laying your prigect before Parliament — I 

 allude to the question whether such a quantity of water as you contemplate 

 sending to the metropolis can be drawn from the chalk without injuriously 

 affecting local interests ? 



That part of my former Report bearing upon this point was vehemently 

 called in question by the Rev. Mr. Clutterbuck, of Watford; and as he and 

 his relatives possess property in the neighbourhood of tbat i)lace, 1 con- 

 sidered it my duty to recommend the Committee to allow Mr. Clutterbuck 

 to suggest any experiments which he conceived were calculated to decide 

 whether the views I entertained were correct or incorrect. 



For this purpose, he suggested that the steam-engines at the experimental 

 ■works near Watford should be kept at work without intermission for three 

 days and nights ; that previously to the pumping being commenced the levels 

 of the water standing in all the adjoining wells should be accurately ascer- 

 tained ; that these levels should at proper intervals be again measured, for 

 the purpose of detecting any change which might take place during the 

 process of pumping. 



I readily acquiesced in every suggestion which I thought calculated to allay 

 those apprehensions Mr. Clutterbuck and others needlessly entertained. 

 Accordingly, on the 3rd day of March, 1841, the necessary preliminary 

 measurements having been made, the engines were set to work, and, at the 

 close of the experiment, not one of the levels of the different wells was 

 found to corroborate the objections of Mr. Clutterbuck ; so far from it, 

 -there was no perceptible difference in any one of them. 



It is only reasonable to exp.'ct that an experiment of this kind, undertaken 

 expressly for Mr. ClutterbuckS satisfaction, and, as it were, under his own 

 direction, would have enabled him to remove from his mind any impressions 

 S3 to the injurious consequences which be had anticipated would result from 

 the establishment of waler-nnrks in the immediate neighbourhood of his 

 property ; on the contrary, he adheres to his preconceived opinions, instead 

 of deducing the most simple, obvious, and only rational conclusions from the 

 facts developed by the experiment made at his own suggestion. 



He addresses a letter to Sir John Sebright, in which he studiously avoids 

 all detail of the experiment made at his express wish, and during which 

 several parties were associated with him in taking the measurements, and 

 brings forward other measurements, and observations made by himself atone, 

 at some prior period, during the sinking of the shafts, when no regularity 

 existed in working the pumps. He never even alludes to the wells in tlie 

 town of Watford, some of which he measured with myself; he does not 

 admit that those levels were taken with a confident anticipation on his part, 

 that they would be instantly lowered when the pumping commenced. He 

 makes no mention of the disappointment on finding, after three days' inces- 

 sant pumping, that those levels were in no degree affected; he makes no allusion 

 to any one of these circumstances or results that so completely negatived his 

 previous positions, and which would have carried couviclion home to the 

 mind of any unbiassed inquirer after truth ; but he proceeds disingenuously 

 to select various levels of wells, taken by him at a distance of several miles 

 from Watford, where it was quite impossible the influence of pumping could 

 extend ; yet all the variation of level in the distant wells he deliberately 

 attributes to the pumping, willtout making the slightest effort to reconcile 

 the discrepancies which would have Ijeen apparent, had be candidly recorded 

 the results of the experiments to which I have already previously alluded. 

 Finding, in fact, that the wells in the immediate vicinity would not tally with 

 tis notions, he calls in the aid of distant wells, where the levels, according 

 to his own showing, were so capricious that anomalies constantly presented 

 themselves, and in the end he adopted a theory at variance with all hydro- 

 statical laws. To discuss it would really be a waste of time, and I think I 

 shall be justified in treating it thus summarily, by stating that it follows 

 from his theory, that pumping at any point in the chalk is not so likely to 

 affect the neighbouring as the distant wells ; and so distinctly is this the 

 tendency of his theory, that he gives a diagram where the level of the water 

 in the clialk is shown to be influenced to a far greater extent at fifteen miles 

 than at one mile dLstant. Previously to the experiment being made at Mr. 



Clutterbuck's request. I fully explained to him the circumstances which had 

 led me to entertain views so diametrically opposed to his own ; I explained, 

 in the most particular manner, that those opinions were forced upon me by a 

 long series of observations which could not be called in qnestion ; still he 

 never refers to the facts which 1 communicated to him. but finishes his letter 

 with an exposition of views totally irreconcilable with them. The series of 

 observations 1 have just meutioned were brought before me during the exe- 

 cution of the Kilsby Tunnel, on the London and I3iriuingham Railway, where an 

 extensive bed of quicksand was met with in the process of tunnelling. Before 

 any progress could be made, it was necessary to drain the sand of water, and 

 for this purpose several shafts were sunk and steam engines erected on the 

 line of tunnel. As the pumping progressed, the most careful measurements 

 were taken of the level at which the water stood in the various shafts aud 

 boreholes; and I was soon much surprised to find bow slightly the depression 

 of the water level in the one shaft influenced that of the other, notwith- 

 standing a free communication existed between them through the medium 

 of the sand, which was very coarse and open. It then occurred to me that 

 the resistance that the water encountered, in its passage through the sand to 

 the pumps, would be accurately measured by the angle or inclination which 

 the surface of the water assumed towards the pumjis, and tbat it would be 

 unnecessary to draw the whole of the water off from the quicksand, but to 

 persevere in pumping only in the precise level of the tunnel, allowing the 

 surface of the water flowing through the sand to assume that iiichnation 

 which was due to its resistance. 



If this view were correct, it was evident that no extent of pumping what- 

 ever would have effected the complete drainage of the bed of sanil. To test 

 it, therefore, boreholes were put down at about 200 yards from the lino of 

 tunnel, when it was clear that, notwithstanding pumping had been going on 

 incessantly for twelve months, and for the latter six months of this period at 

 the rate of 1800 gallons per minute, the level of the water in the sand, at a 

 distance not exceeding 200 yards, had been scarcely reduced. 



The simple result, therefore, of all the pumping was merely to establish 

 and mairttain a channel of comparatively dry sand in the immediate line of 

 the intended tunnel, leaving the water heaped up on each side by the resist- 

 ance which the sand oflfered to its descent to that line on which the pumps 

 and shafts were situated. 



Observations of this description were continued for upwards of two years, 

 and it is upon them that I rest my views respecting the drainage of the 

 chalk, or any other porous stratum or mass, by means of pumps concentrated 

 at a focus ; indeed, when once suggested, it seems so self-evident that we may 

 with considerable confidence predict the results of any pumping operations, 

 under such circumstances as are found to exist in sand, chalk, or any rock 

 or material, presenting resistance to the free motion of the liquid flowing 

 through it. This resistance is unquestionably represented by the angle of 

 inclination which the surface of the water assumes, and this, again, is no 

 doubt much influenced by the size of the fragments of which the same may 

 consist, thus giving rise to a variety of modifications in the slope of water, 

 in difl'erent directions, from the focus of pumping. 



If the above views be correct, and of which, supported as they are by 

 indisputable facts, there can be no admission of a doubt, it follows that the 

 result of pumping at a deep shaft, in chalk or other similar porous material, 

 would be the drainage of a portion of the district, represented by an inverted 

 cone, the point being at the bottom of the shaft ; the upper surface, or what 

 is generally designated the base of the cone, occupying an area depending on 

 the inclination which the fluid assumed in passing through such porous mass. 

 This inclination must vary with the character of the material, but in no chalk 

 that I have ever met with can it be inconsiderable ; consequently, from no 

 extent of pumping at any one point in a formation like chalk, can the influ- 

 ence be apparent at any great distance. 



Before I commenced the above remarks, it was my intention to have 

 extended them into greater detail, hut I found that adducing abstract calcu- 

 lations would tend rather to obscure than to elucidate tbat which is really 

 clear and simple. I have, therefore, contented myself with such a statement 

 as will convey, I trust distinctly, my views, and the reasons upon which they 

 are based, and I am not without hope that the following facts are established 

 — viz. : — 



1. That the chalk is the '• great water-bearing stratum" underlying the 

 London clay, and from which all the Artesian wells, directly or indirectly, 

 draw their supplies. 



2. That below the level of its natural drainage of the country it is charged 

 with an enormous quantity of water, which may be obtained with extra- 

 ordinary facility by pumping. 



3. Tbat the quantity obtainable from shafts is amply sufficient to meet the 

 object contemplated by the Company. 



These facts established, it is scarcely possible to believe tbat any who are 

 interested in the supply of the metropolis with pure water will hesitate in 

 assisting you in carrying out your project, and I cannot conclude without 

 expressing an ardeut'wish that'the subject may he treated by alt parlies in a 

 Uberal and impartial spirit ; and I am persuaded tbat this new source of 

 supjily of water will soon be made available for the most important capital in 

 the world. 



Robert Stephenson. 



