1850.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



395 



and badly tasted; and from what cause ? Simply because water has an ex- 

 traordinary capacity for absorbing the impurities of the atmospliere. 



Referring again to the plan of collecting rain-fall by draining the sandy 

 heaths, I question whether it could in one case be carried out with advan- 

 tage — namely, on the higher levels ; as, for instance, the crests of the Fox 

 Hills and Chobhara Uidges, where the strata of sand are of a very loose 

 nature. I think that the surface once broken through, the water would pass 

 by the pipes. The area on which this would happen is, however, not very 

 large. It is very desirable to ascertain this point by trial works ; a few 

 acres drained would satisfactorily settle an important question. The same 

 would occur in the lower levels were it not that nature has abundantly pro- 

 vided a subsoil in the form of a crust or pan about 9 inches thick, composed 

 of 3 inches of closely-packed pebbles and sand resting upon 6 inclies of 

 sandstone. This pan lies at a depth varying from 1 to 3 feet below the 

 surface; in some cases it is found beneath a few inches of sandy loam. The 

 pipes might be laid on the pebbles and sand incrusted together, which would 

 hold the wafer. The pan once broken through the water would, I fear, be 

 lost for ever. The cultivation of these heaths would eventually repay a 

 large portion of the expense of collecting a rain-fall by drainage. Mr. 

 Hewett, a most intelligent farmer and land surveyor, from whom I have 

 obtained much valuable information, assures me that v^bere this pan comes 

 near enough to the surface to be broken through, which is done at an 

 expense of SI. or 10/. per acre, and when properly manured, the cultivation 

 pays. 



The only disadvantage attending the Board's scheme, if in such an im- 

 portant matter it may be deemed so, is the expense of the large lined storage 

 reservoirs necessary to contain a six weeks' or two months' supply for a city 

 of the giant proportions of London ; otherwise the system is unique in sim- 

 plicity and peifect adaptation for the purpose required. So vivid was this 

 impression on my mind, that on developing the idea of supply from springs, 

 I conceived a method of adapting the principle to my own case. Where the 

 springs are large, I propos.'i to inclose them in brick or tiles, but when small 

 and numerous 1 would prefer to gather them in one stream to be led away in 

 pipes ; but this must be effected on the pure sand, and great care must be 

 taken to avoid the mixture of surface-washing. In the case when leading 

 away a stream of springs it would be liable to discoloration from heavy 

 rains, I propose to provide a remedy by preparing at the point of diversion 

 from the natural channel a new bed for a short distance at a less inclination. 

 The bed to be a trench with a pipe at the bottom, and filled up with small 

 stones and sand, heather or heath being placed round the pipe joints. The 

 stream being led on this new bed will percolate into the pipe beneath. When 

 the extent of the ground above the springs would expose them to be choked 

 up by rubbish and dirt after a storm, I would intercept the rain-fall in con- 

 tour trenches with pipes underneath them also, and lay a branch to lead the 

 water aw.ay to the main. I have shown both these plans as adapted to the 

 case of Farnhara-hill, and a large addition might thus be made to the flow 

 of the springs if desirable. 



Hereafter I propose to detail my arrangements of branch Imcs from the 

 spring-beads, leading to mains terminating on Wimbledon-common ; giving 

 also an estimate of the expense of the entire schemeworks, compensation to 

 mills, &c., also some general information on the collateral advantages of a 

 pure soft water supply — the results of some experiments I am making on the 

 action of sand as a filter, and some qualitative analyses of the springs. 



The annexed plan is that of Farnhani-hill, reduced from the Tithe Com- 

 mission plan, and tested as to accuracy. The blue contour line represents 

 the level of the springs. I have gathered them together and gauged their 

 flow as accurately as in my power. Their daily discharge is equal to 

 897,393 gallons. " 



The area within the contour line is 571 acres. The available rain-fall 

 from 22'G5 inches per annum ; a mean of 30 years' register at the Military 

 College, Sandhurst, allowing the usual deduction of 14 inches for evapora- 

 tion and absorption, is 279,858 gallons per day. The difference, then, 

 611,160 gallons, is the least figure in favour of ray assertion that the water 

 in this hill is due to rain-fall elsewhere, for the rain on the hill does not 

 percolate, but passes away. 



I assure the Board, however, that a careful collection of these springs 

 would double their volume, and produce a daily discharge of 1,794,786 

 gallons. This, then, leaves a total of 1,514,928 gallons above the available 

 rain-fall on the hill, supposing it all to penetrate. The plan also shows the 

 hill drained above the springs on the principle already alluded to. The 

 section of the pipes and their outfall is calculated in proportion to the 

 quantity of rain likely to fall in the shortest time, according to the prin- 

 ciple laid down by Mr. Chadwick. 



In reference to my idea of the cause to which these springs are due, I 

 would mention that a notable instance of the kind occurs in Hongkong, an 

 island mountain of not 25 mUes in circumference at its base, and of 1000 or 

 12,000 feet elevation above the level of the sea. The quantity of water 

 supplied from springs on the top of this mountain is notoriously far be. 

 yond its rain-fall, which latter, from the declivity of the other ground, is at 

 once discharged into the sea, as all who have been there are well aware of. 

 The shore of the mainland is not further than two miles and a-half, but 

 the range of mountains of equal and higher elevation, and which furnish 

 the supply, are at a distance of upwards of ten miles. Tne rain-fall cannot 

 find its way again after percolation to the surface, and is necessitated to find 



its level by crossing the sea and rising through the fissures of the granite 

 formation of Hongkong. The springs are rarely known to be affected in 

 quantity even after a three months' drought in the island, the thermometer 

 often at 80° and upwards in the shade. 



Tbc advantages 1 propose to derive from permanent springs, that is, 

 always preserving an average flow of summer and winter, over surface 

 drainage, are twofold : — 



1. The continuous flow from springs gives water of better quality as to 

 aeration and temperature. 



2. An immense saving will be eflected on the item of storage reservoirs, 

 and, I believe, a considerable sum in the diminished quantity of excavation 

 and pipage. Assuming that the supplies from these springs do not mate- 

 rially alter, no necessity can exist for storage reservoirs. A covered reservoir 

 for two days' supply might he provided at Wimbledon-common to meet any 

 extraoulinary emergency ; otherwise, amain with a simple waste-pipe into 

 the Thames woidd suffice. 



Too much importance cannot be attached to a constant flow of pure, cool, 

 and soft water, brought direct without detention from the Ilindhead to the 

 attic of the highest house in London. How grateful will be the daily use 

 of cool soft water only 24 hours from a natural reservoir in the depth of 

 the earth ! 



I consider I have realised, in a remarkable manner, the Board's enunciation 

 — " The nearer the source the purer the supply." The whole value of the 

 scheme appears to me to depend on the accurate following-up of this 

 principle. 



On consideration of the original proposal, there is only one more point I 

 shall at present touch upon — namely, the great and scarcely estimable 

 benefits of land drainage, not only to the soil, but to the inhabitants of the 

 district. From the rain-fall, a depth in the year of 22-65 inches (allowing 

 seven to be absorbed), there remains nearly 15 inches, or 1529 tons of 

 water on every acre, impeding cultivation by diminishing the temperature of 

 the soil, by not allowing a proper circulation of air iu it, and by causing a 

 perpetual evaporation, not only injurious to health in itself, but excessively 

 wasteful of the heat of the atmosphere, a loss which in our damp climate 

 is a very serious consideration indeed ; and it is only when the whole country 

 shall have been perfectly drained that this stigma of unnecessary and dan- 

 gerous damp will be efiaced from our registers of temperature. 



Again, experience has satisfactorily shown {vide the Report on the Water 

 Supply) that the low temperature of undrained land is the chief cause of 

 scanty and poor crops, and inferior growth of timber. In an economical 

 point of view, it is most necessary then to remove this noxious agency. 



Having given the results of my observations iu detail, it may be now 

 proper that I should state my opinion of their variance as compared with the 

 conclusions enumerated in the report, which difference I attribute to the 

 limited investigation of the subject. 



Generally, in all points as applied to the quality of water, its advantages 

 in economy, its beneficial influence on health, &c.., my experience not only 

 distinctly confirms the views of the Board, but has elicited further illustra- 

 tions, in respect to which I hope shortly to have the honour of addressing 

 them. This information I have collected from persons of all classes, me- 

 dical men, manufacturers, farmers, tradesmen, peasants, Sec, all of whom, 

 in their difi"ereut spheres, have given me valuable evidence on the subject in 

 question. 



The results of my experience are as follows : — 



I. With respect to the quantity and quality of water to be derived from 

 the gathering-grounds, in whatever method of collection — the report gives 

 28,000,000 of and under three decrees of hardness. My results give 

 40,000,000 of and under one degree, and 10,000,000 of and under two 

 degrees of hardness. This improved quality is gained by my development 

 of the principle of taking the water from its source (that is, where it issues 

 from pure sands), and leading it away before it can be affected by contact 

 with soils. I beg to express my convi'ction that the purity will depend 

 entirely on the careful exer:ution of the work; it would give, to recapitulate 

 its qualities, 40,000,000 of water, of primitive purity ; perfect as to aera- 

 tion; of a grateful temperature, about 30 degrees; brilliant in colour ; soft 

 almost as distilled water ; and almost free from all mineral, animal, and 

 vegetable impregnation, suflicing for the supply, at the estimate of 75 gal- 

 lons per house, of 523,150 houses.— The 10,000,000 of aud under two de- 

 grees of hardness are derivable from sources rising in sands not quite pure. 



II. By the direct means of collection from springs, instead of the exten- 

 sive system of land drainage originally contemplated, very considerable 

 saving of expense would be effected: — 1. In the less quantity of pipage 

 required, and, consequently, of labour expended. 2. On the item of the 

 large extent of storage reservoirs, originally required to provide for summer 

 months, periods of drought; and which, by my plan, would be unnecessary. 



3. On the reduced claims for compensation, especially as no breadth of land 

 would be required to be taken up. In fact, after collection, on descending 

 into the lower levels, the mains would lead along and just outside the lines 

 of railway. A mere underground right of way — a pipe-laying easement — 

 would be required. 



A rpsMmt'of the above then gives, in favour of the plan proposed — 1. 

 Greater certainty of supply. 2. Superior quality. 3. Greater abundance. 



4. Greater speed of execution of work and application for service. 5. 

 Greater economy. 



52* 



