192 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[June, 



liundred yards, Mr. McGregor's well, from long continued pump- 

 ing below low water, has thus become charged in a remarkable 

 manner » ith sea salt, and there are many other well-known in- 

 stances all tciuling to establish the fact, that when wells, especially 

 if near the river, are pumped below the level of low-water mark, 

 tlie permeability of the sandstone is such as to admit of impure 

 water flowing iiito them. And this result is in perfect accordance 

 with the views I have explained, and corroborates the statement of 

 the mode in w hich the sandstone is drained by the pumping in 

 individual wells. 



Tlie Booth Works. 



All these circumstances point out the impropriety of relying 

 much, or even to any extent, upon an increase from deepening the 

 existing public wells. To this remark Bootle may perhaps be 

 made an exception, as the level of the water at the works there is 

 so much aliove high-water mark, and cannot for some time be 

 reduced to it ; hut their proximity to tlie river is such that any 

 considerable deepening, accompanied by the abstraction of much 

 larger quantities than at present, would even in them be likely to 

 be attended by an influx of water from the river. 



The Bootle \Vorks furnish a very p-ood example of the free com- 

 munication through the sandstone by fissures or otherwise, from the 

 circumstance of the water in a quarry at a distance of about half a 

 mile being much influenced in level by the rate of pumping at the 

 Water 'Works. The foreman (John Prescott) states distinctly 

 tliat the Bootle Quarry maintained the level of water at about 54 

 feet from the surface from the time of its being opened until the 

 engines at Bootle commenced working night and day, when the 

 level of the water sank to 60 feet from the surface; and that when 

 this rate of pumping ceased and the water was allowed to accumu- 

 late in the reservoir at Bootle, a corresponding rise took place in 

 tlie level of the water in the quarry, and prevented the works pro- 

 ceeding in the manner deemed most eligible. 



The Bootle Works also afford a very interesting and instructive 

 lesson as to the efl"ect of bore-holes, and clearly demonstrate that 

 the increase of their number with very varying depths does not 

 regulate the quantity of water to be ohtained by their means. 



In the reservoirs at these works there are 16 bore-holes, each of 

 them having been made for the purpose of supplying an additional 

 quantity of water. Their efficiency was thus tested. The reser- 

 voirs having been pumjied dry and all the bore-holes tightly 

 plugged, the supply to the reservoirs when in this condition was 

 small, consisting only of some leakage through the bottom, and 

 what came from the engine well. The plug was then removed 

 from a bore-hide 308 feet deep, and the yield was ascertained to be 

 at the rate of 921,192 gallons per 21 hours. A second bore-hole 

 .599 feet deep was next unplugged and the yield increased to 

 949,461 gallons; and so in succession each of the remaining bore- 

 holes was unplugged until the whole were opened. By referring 

 to Table No. 7 in the Appendix the result of each step of the ex- 

 periment will be found recorded, and it will be observed that the 

 total increase by opening 15 bore-holes amounted only to about 

 112,792 gallons per 24 hours, being little more than an addition of 

 one-tentli to the yield when only the first was unplugged. But 

 the first experiment, showing a yield of 921,192 gallons, although 

 important, is not entirely free from objection, arising out of the 

 circumstance of the passage of water from the plugged bore-holes 

 through fissures in the rock between them and the lodgment or the 

 engine well. 



It may be inferred from the evidence of Thomas German the 

 engine-man at Bootle, that as each successive bore-hole was put 

 flow n an increa'-e of water was at first obtained, and the circum- 

 stances attending one or two of them would lead to the snpjiosition 

 of the supply being derived from independent fissures; they are 

 now, however, all more nearly in a state of equilibrium, and in 

 effect deriving their supply from one common source. If a pump 

 were applied to the first of the bore-holes which was unplugged 

 and the vvater drawn from it as quickly as it flowed, the yield of 

 the neighliouring bore-hole-; would immediately almost cease, their 

 ( ontents being absorbed by the pump; or if the arrangement be 

 I h:iiiged, the same anKuint of pumping pow I'r distriliuted amongst 

 the entire number of bore-ludes, each would yield a quantity 

 similar to that which flows into the lodgments under the ordinary 

 course of working. Every .-iddition to the pumping power would 

 equally lower the level of the w.ater in each bore-hole, and these 

 results could only be modified by the lateral communications 

 between the bore-holes not being uniformly ]>crmeable, but it is 

 evident from the above experiment, where the flow was interfei-ed 



with so little by the majority of the bore-holes being plugged, that 

 great uniformity exists in these channels of communication. 



This group of bore-holes at Bootle presents a complete epitome 

 of what is actually going on upon a large scale throughout the tow n 

 of Liverpool. The dift'erence is only one of degree, consisting in 

 the intervention of a large mass of rock between the wells, which 

 ofl^ers more difficulty to the free passage of water from one to the 

 other. 



Source of Supply. 



But, before referring more particularly to the wells in the town, 

 or their influence upon each other, I may state my idea generally 

 as to the source of the supply, and the mode of its distribution in 

 the sandstone. 



I conceive that the source from which all the strata and fissures 

 in the sandstone become charged, is the rain falling upon the sur- 

 face of the surrounding country; that so soon as they are fully 

 charged the surplus overflows and is discharged into the adjoining 

 brooks and rivers; and that the rain which falls upon the surface 

 and finds its way into the fissures, passes through apertures or 

 channels of limited area, and wiU consequently form an inclined 

 plane towards the easiest outfall, the angle of this plane with the 

 horizon varying slightly, according to the wetness of the sea.son. 

 This view is illustrated by the outfall along the margin of the River 

 iVIersey, of a number of springs deriving their supply from the in- 

 clined plane of water which rises towards the high ground of Ever- 

 ton and Edge Hill; and such is generally the state of things when 

 wells are first sunk. In order that a well should yield a supply of 

 water at all seasons, it must be carried below the extreme fluctua- 

 tions of the angles described; and the effect produced upon the 

 plane by sinking a number of wells below it, and extracting water 

 from them, would be to form a series of indentations, varying in 

 depth and extent, according to the intensity of the draught and 

 the permeability of the strata. 



These views are somewhat similar to those expressed by Mr. 

 Newlands and Mr. Rowlandson, and are corroborated by the 

 elaborate sections of wells furnished by the former gentleman re- 

 presenting their depths with the usual level of the water in them. 



Periodic Influences. 



It is now necessary to advert to the theory of Mr. Gage respect- 

 ing certain periodic influences to which he ascribes the rise and 

 fall of the level of the water in the wells. For the purpose of 

 illustration, he has favoured me with a section which shows the 

 highest and lowest levels of the water during each week, from 

 January 1846, to June 1847, which are prepared with care, and 

 exhibit well the facts they represent. 



I cannot, however, arrive at the same conclusions with him. 



The first section, referring to the Soho station, shows, from 

 January to March 1816, a gradual elevation of the level of the 

 water, and from March to June, a gradual depression. Following 

 the section, we find that from June to August, there is a consider- 

 able rise, which is no doubt attributable to the bore-hole made 

 about that period, and probably to the fact stated by Mr. M'Donald, 

 that the pumping at this station was not then so continuous as 

 before, owing to the Windsm* engine being worked for more hours. 

 From August 1846, to Januai-y 1847, this elevation is very 

 steadily maintained, but then declines to the follow ing May and 

 June, indicating, perhaps, to some extent, the falling off of the 

 first accession of water from the bore-hole, which is stated to have 

 been in progress between August 1846, and May 1847. 



The general contour of the section, after the boring, certainly 

 affords no proof of the periodic rise in March, broached by Mr. 

 (iage; and as he does not give the weekly quantities pumped from 

 the well, there are no data to show that the undulation in the 

 levels did luit arise simply from the abstraction of varying quan- 

 tities of water during the periods to which reference is made. If 

 there be any such influence, it appears to me that it would operate 

 entirely against his opinion of the chief supply of water to the 

 sandstone being derived from beneath. But this subject, although 

 of considerable interest in a philosophical point of view has not 

 really any important practical bearing upon the question before us. 



In oi'der, however, to ascertain the fluctuation which the level 

 of the water does undergo in the different wells, I have prepared 

 and given in the Appendix, sections for the year 1849, exhibiting 

 the greatest and least heights, with the important addition of the 

 ([uantities pumped out each week; thus affording an opportunity 

 of judging whether the variations at dift'erent seasons are not truly 

 ascribable to this cause. The examination of these sections has 

 perfectly convinced me that the levels of the water in the several 



