1842.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



239 



Both the chalk and sand are extremely porous, and there can be no ques- 

 tion that each of the "belts" of country occupied by their outcrops con- 

 tributes alilic its share to the supply of the great reservoir of water 

 covereiP by the London clay. 



In the construction of Artesian wells in or about London it is obvious, 

 therefore, that the supply docs not come immediately from the plastic clay 

 sands ; hut this does not militate against my conclusion, that the reservoir 

 formed by these sands is supplied principally by the absorption of rain, 

 through the medium of the chalk, which occupies far more extensive areas 

 than tlie plastic clay sands, and consequently possesses (even though it may 

 not be so porous as sand) infinitely greater powers of absorption. 



Mr. Webster tlien proceeds to state, that where wells are sunk through 

 the London clay into the chalk, the water which the latter yields is most 

 probably derived from the water-bearing stratum " above it. 



That this was the case in the Ilampstead-road well (the instance quoted 

 by Mr. Webster), I am not prepared to deny, though I much doubt the fact ; 

 but it cannot be considered conclusive against the supposition of chalk being 

 extremely porous and absorbent, especially as innumerable examples may be 

 referred to in every district occupied by the chalk, as incontestable evidence 

 in its justification ; moreover, many instances exist, even in London, where the 

 supply of water to wells sunk to the plastic clay sands having proved insufficient, 

 it has'become necessarj-to sink them into the chalk, when an increased supply 

 has been invariably procured ; for example, in the wells at Messrs. Meux and 

 Keid's breweries, at those at Greenwich Hospital, and Mr. Nicholson's dis- 

 tillery, the necessity has arisen, and been met successfully by such a process. 

 And since no particulars can possibly be given of the sinking into the chalk 

 in the Ilampstead-road well, no general inference as to the contents and 

 capacity of that formation should be drawn from it, more especially as other 

 examples, upon a much larger scale, such as those above mentioned, may be 

 quoted to prove that an augmentation in the feeders is immediately consequent 

 upon penetrating the chalk below the sands. 



I am well acquainted with the chalk district between Watford and Tring, 

 and it having devolved upon me, in the course of my connexion with the 

 London and Birmingham Railway, to sink a great number of wells in the 

 chalk, my attention has been particularly called to the extraordinary quantity 

 of water existing in the chalk immediately below the level of the natural 

 drainage of the country — that is, of the adjoining streams, and I was at the 

 same time struck with the conformity apparent between the surface of the 

 subterranean reservoir of water and the natural surface of the country. 



The evidence which the valley from Watford to Tring affords in reference 

 to this point, is replete with interest, for it establishes beyond all question 

 that the water absorbed by the chalk is held up to a very high level towards 

 the edge of the basin ; indeed, there is sufiicient evidence in the district just 

 mentioned to prove that the surface of the water absorbed by the chalk 

 assumes an inclination corresponding almost exactly with tlie declivity of the 

 valley by which tlie district is drained. Thus, near Watford and in the vicinity 

 of the river Colne, all the wells require to be sunk to the level of the Colne 

 before the supply of water is obtained ; but as we proceed up the valley 

 towards Boxmoor, Bcrkhampstead, and Tring, water is procured at levels 

 corresponding strikingly with the inclination of the valley, far above the 

 levels of the water in the wells at Watford. 



The Tring cutting on the London and Birmingham Railway presents 

 another forcible example of the constant and rapid absorption of water by 

 the chalk. In the execution of that cutting a very large quantity of water 

 was encountered, notwithstanding the situation was on the summit of the 

 chalk ridge, forming the actual l)rlm of the basin, where it could not be 

 supplied with any water but such as fell upon the immediate neighbourhood, 

 yet it yielded upwards of one million gallons per day, and continues to 

 yield an extraordinarj- quantity up to this hour, without any sensible dimi- 

 nution. 



This is surely incontrovertible evidence that the chalk absorbs water witli 

 the utmost facility, and as a consequence, when the levels are suitable, 

 readily yields it up again. It may not be uninteresting to add, that previously 

 to this work being commenced, attempts were made to sink wells to test the 

 material from the surface of the land to the intended ilepth of the cutting; 

 hut so freely did the water flow from the chalk, that it was found impossible 

 to sink several of them by ordinary means to tlie deptli of 60 ft. Similar 

 results have followed all experiments of this kind which I have witnessed, 

 and those who are best acquainted with the sinking of wells throughout dis- 

 tricts occupied by the chalk formation, concur in the opinion that it should 

 be regarded as an enormous mass of rod saturated trith water, which it 

 yields with the utmost rapidity, by the action of a very small hydrostatic 

 pressure. 



I might here enter into a minute detail of the levels of the wells sunk in 

 the districts occupied by chalk, which have come under niyoliservation, were 

 I disposed to extend this report to an unusual length ; but I beheve it will 

 be more satisfactory to the committee that I should allude to the results 

 which have been laid before me by the gentlemen who were deputed by me 

 to examine waterworks, which are known to derive their supply entirely 

 from such wells ; with this impression, therefore, I transcribe the following 

 extracts from the reports which have been placed before me : — 



WiNciiESTEu. — This town is at present supphed by wells. There is a well 

 that has lately been sunk on the hill, near the barracks, entirely through 

 chalk, to the depth of 170 ft. ; near the bottom there are fissures, out of 

 which the water rushes with considerable TioUnce ; the water rises about 



10 ft., and after pumping for seven hours successively, it is reduced 2 ft_ , 

 but immediately the pumps stop working it rises again to the same height i n 

 15 minutes. 



The water is raised by the aid of an 8-horse engine working a 6-inch 

 pump, 2 ft. stroke, and from 18 to 22 strokes per minute ; at 18 strokes per 

 minute the pump lifts 44 gallons, or 31,680 gallons per 12 hours. 



At the railway station there is another well sunk in the chalk, to the depth 

 of 80 ft. ; at Christmas time there was about 4 ft. of water, and in April 

 about 12 to 14 ft. In October, a month when the springs are generally low, 

 the engine was kept constantly at work, day and night, for 4 or j weeks, and 

 could not lower the water beyond 2 ft. from the bottom. In July, last year, 

 after working the pump for an hour and a half, the water could not be 

 lowered more 18 inches. The quantity the pump lifts is the same as described 

 above. The engineer never knew a deficiency. 



Through the town of Winchester there is a very fine stream of water, 

 which rises from the chalk hills. 



I was informed, at Winchester, that at Sir William Heathcote's seat at 

 Merdon Farm there is a well in the chalk, 331 ft. deep; the water appears 

 to pass across it like a river, with a rapid current. 



Sir Thomas Baring, at his seat at Stratton Park, has sunk a well in the 

 chalk, and is now having a steam engine erected for lifting the water to 

 supply his estate and mansion. 



Arundel. — There is a well at the bottom of the town, which supplies 

 nearly the whole of the inhabitants of that portion. It is stated to be only 

 20 ft. deep, sunk in the chalk ; a deficiency has never been known. 



The upper part of the town and the castle are supplied from a spring, 

 which rises from the chalk in the valley, on the south-west side of the town, 

 where there is always an abundance. 



Brighton. — The whole of this town is supplied with water obtained from 

 the chalk, either by wells or from the water-works. The water-works are 

 situated about a mile from the town, on the Lewes road, adjoining the 

 barracks. The surface of the ground at the well is 64 ft. above high water 

 mark. A well has been sunk to the depth of 97 ft. ; at 16 ft. above the 

 bottom there are four adits driven in from the sides of the well, to the extent 

 of 46 ft. each, and about 6 ft. square ; they are driven north, south, east, 

 and west ; the water flows into these adits from fissures in the chalk, in very 

 considerable quantities, and appeared to flow towards the sea. 



The water rises to difler,«:nt heights at various periods of the year ; it has 

 been as low as 58 ft. 6 in. from the surface, or 38 ft. 6 in. of water, and as 

 high as within 8 ft. 10 in. of the surface. In the present month of April, 

 when I viewed the works, before the engine commenced working, it stood at 

 31 ft. below the surface, or 66 ft. of water, and after the pumps had been 

 working 12 hours, the water was lowered 2 ft. 9 in. ; it will regain that quan- 

 tity in a very' short time after the pumps have ceased working. 



The water is lifted by an engine of 20-horse power, working three pumps 

 8} in. diameter, and three pumps 8,i ill. diameter, both 18-inch stroke, and 

 1.") strokes per minute, lifting together 231,840 gallons per 12 hours, the time 

 the engine works daily, Sundays excepted. 



Previously to the Company being formed, there was a strong opposition in 

 the town, and a cry that " all the wells would be dried up," but since the 

 works have been in operation, there has not been a single complaint. The 

 only well that was effected was one close to the works in the barrack yard : 

 this well has been lowered a few leet, and no complaints of want of water 

 have arisen since then. 



The supply at present is to about an eighth part of the town, besides for 

 watering tlie streets, and it is daily increasing. The quantity is amply suffi- 

 cient for the whole lown. When the springs were low in June, 1840, the 

 six pumps were kept working day and night, for eight days, when the water 

 could not be lowered more than 12 ft. 



The pumps are fixed in the well in such a manner that either set can be 

 raised or lowered, according to the height of the water in the well. There 

 are two rising mains 9 in. diameter, (one to each set of pumps,) and an 

 air-vessel, 4 ft. diameter, C ft. high ; tlie delivery-pipe from tlie air-vessel is 

 12 in. diameter ; near the exit it is furnished with an air-valve and a steelyard 

 lever, loaded witii about 80 lb. The water is conveyed througli a 12-inch 

 main, about a mile in length, to the reservoir, the bottom of wbirh is 113ft. 

 above the top of the well, and the surface 120 ft. The water is crmveyed 

 from the reservoir by a 10-inch main to supply the eastern part of the town, 

 and a 12-incb main, to the old Stein, then 10 in.; there are branch mains, 

 from 5 to 10 in. diameter ; the service-pipes vary from 2 to 5 in. diameter. 



Dover. — This town is entirely supphed with water from wells sunk in the 

 chalk, and from the water-works' at the lower level of the towns in Mr. Wal- 

 ker's vard, where there is a well sunk in the chalk lielowthe clift"; the surface 

 is 10 ft. above high water mark, the depth is 33 ft. 6 in., and the diameter 

 12 to 13 ft.; it is a tidal well; when high water, there is about 10 ft. of 

 water, and at low water, 3 ft. The water is lifted by the aid of a 25.horse 

 engine working two pumps, 8 and 9 in. diameter. 3 ft. 6 in., and 3 ft. stroke, 

 and 18 to 20 strokes per minute; at the rate of 20 strokes they lift 317 

 gallons per minute, or 228,240 gallons in 12 hours; the water is lifted 160 ft. 

 to the top of a tank. 



This well supplies about 50,000 gallons jicr diem. There is another supply 

 obtained at the gas-works, lifted hy the aid of a two-horse engine. 



Deal and Walmer. — Water-works have been lately erected about a mile 

 to the west of Deal, which obtain their supply from a well 120 ft. deep and 

 6 ft. diameter, the surface beiug 90 ft. above low water mark ; there is 16 ft. 



2 L 2 



