trifles, and the great principle that each watershed district is by nature indicated, and is complete within its orographic boundary, is recklessly disregarded.

It is remarkable to see how a natural source, to which no objection occurs, and to which it is more than probable that we shall hereafter have recourse for the drinking-water of London, has been not only neglected, but carefully shut out, at considerable cost, by the water companies. On the occasion of constructing a reservoir near Walton, on the Surrey side of the river, the prosecution of the work was impeded by the ready flow of water through the gravel which was being excavated for the purpose. Clay underlies the gravel, and the supply comes from the watershed of the chalk hills of Surrey. No water is more pellucid than that which wells out from these hills. At Albury, near Guildford, on the estate of the Duke of Northumberland, is a natural reservoir, or true fountain, called 'The Silent Pool,' which rises from the chalk, and is so perfectly transparent that the reflections of the trees around it are almost indistinguishable from the objects beneath the surface. The depth, which is considerable, seems to be only a few inches. The flow is perennial, and the spot resembles the well-like heads of some of the great Asiatic rivers more than anything to be found elsewhere in England. This exquisite spring is a sample of what may be derived from the Surrey chalk. At Walton the reservoir lies above the level of the Thames, from which the water is now supplied by pumping engines. In that case the company interested incurred great trouble and cost in keeping this magnificent supply out of the reservoir, in making that receptacle water-tight, and in pumping into it the polluted water of the Thames. Favour

able accident had opened to them a source of natural wealth. They not only threw it away, but went to great cost to exclude it. The question of water supply, as far as quantity and quality were concerned, offered its own solution. It was not perhaps secundum artem to take a lesson direct from nature. The pure water was walled out, and the impure water was pumped in (though the former cost nothing, and the latter involved a constant cost), and so we believe it remains to this day.

The principle that each great natural basin or watershed district is to draw its supplies from its own rainfall is one which no denselypopulated country can afford to neglect. Any such schemes as those which have been projected for bringing the main water supply of London from a distant watershed are fraught with the gravest objections. These schemes have not been deficient either in number or in audacity. Mr. Bateman, in 1875, proposed to intercept the head waters of the Severn, and to bring them in an aqueduct or artificial river of 180 miles in length, from the highland district between Snowdon, Plynlimmon, and Cader Idris to Stanmore Heath. The fall from one end to the other of that channel is about 270 feet; but the water would have either to be led up hill and down hill through syphon pipes or to be carried over deep valleys by lofty aqueducts. The design contemplated the supply of upwards of a million of metric tons per diem, and the reservoir was to be adequate to hold the consumption of fifteen to twenty days.

Messrs. Hemans and Hansard proposed to tap the Lakes of Cumberland and Westmoreland, and to bring the water of Thirlmere, Haweswater, and Ullswater by an artificial channel, of 240 miles in length, to supply the metropolis. The level of the last-named lake,

which is both the largest and the lowest of the three, is 480 feet above the sea. The district comprising the lakes has the heaviest rainfall in England. In 1872 the rain gauge at the Stye Head Pass registered the fall of 243.98 inches of rain-quite a tropical quantity. In North Wales, in the same year, the heaviest fall was one of 150.21 inches, at Bedgelert.

Mr. Hamilton Fulton proposed to intercept the supplies of the headwater of the Wye, forming a reservoir at Rhyader, 590 feet above the level of the sea. The length of the artificial channel would be approximately the same as that of Mr. Bateman's scheme-180 miles. Stanmore was the locality selected for the London reservoir of this project.

Mr. Remington proposed to abstract the waters of the Dove, commencing his artificial river at Milldale, on that stream, at a height of 586 feet above the sea, and carrying it to Barnet, where the London reservoir was to be at the level of 300 feet above the sea. As far as rainfall observations go the supply of this district would be totally inadequate to meet the requirements of London, apart from any other objections.

The population of the greater London of the Registrar-General, which covers an area of 698 square miles, amounted in the last return to nearly 4 millions of persons. Nearly a million more has to be added for the population of the remainder of the district which is now supplied from the Thames and its affluents. At least 250,000,000 tons of water per annum must be conveyed by any system of supply that is intended to serve this great population, or to displace the natural source of their supply, the watershed basin of the Thames itself. And although, within the last few years, London has shown indications of a decline in the rate

of increase which has for some time prevailed, and which was such as to double the population in a period of 40 years, yet provision for a very extensive annual increase must be made in any plan that proposes seriously to meet the requirements of the case. It is obvious that if it were attempted to raise the funds for either of the gigantic schemes that we have cited, capital could only be found on the security of a general water-rate. That is to say, the new company must be invested with the sole right of supply. If any option were left in the matter, the companies already in possession of the ground would be able, by combining, to lower their rates for a time, and to starve out a competitor weighted with so enormous a capital. In any case of gradual improvement in supply matters would in course of time adjust themselves. But to effect

total revolution, revolutionary measures must be taken, and power of enforcement given to the new purveyor of water. Considering

the sum that is invested in the existing waterworks, the probability that Parliament would grant such powers is so low as to be out of reasonable calculation. We have seen on a former occasion that the price at which water is now supplied in London is under three halfpence (more accurately one and fourtenths of a penny) per metric ton. At that rate, London and the Thames Valley consumers would pay a little under a million and a half per annum for the improved supply. But London already pays to the existing water companies 1,165,000l. per annum, out of which sum only a little more than half (662,000l.) is received in the form of interest and dividend on capital by the owners of the waterworks in question. The maintenance of a river of a couple of hundred miles long, running across the backbone of England, would, of course, add much to the expen

diture of a lake, or a Welsh river supply, as compared to that of a supply taken from the Thames. But under the new arrangement it would be necessary to continue this payment, or in some way to compensate the existing proprie tors. Interest would have to be added on the new works, the cost of which Mr. Bateman estimated at eleven millions sterling, requiring an annual payment of at least 550,000l. more. Thus up wards of 1,200,000l. would be required for interest. A further sum of 800,000l. would probably prove quite inadequate to meet maintenance of works and cost of distribution. Thus an increase of nearly 50 per cent. in the waterrates would be an immediate result of the adoption of either of the schemes for supply from a distant source; and it is probable that such an increase would by no means prove sufficient to meet the requirements of the case.

With regard to to the natural sources whence the 250,000,000 tons of water required for the annual need of the metropolis and the Thames Valley inhabitants may be derived, there is really no room for hesitation. An inch of rainfall, over an acre of ground, amounts to 100 tons of water. This is an extremely simple and convenient unit for calculation. The area of the Thames basin above the pumping stations of the metropolitan water supply at Hampton is 2,352,640 acres. The area below that line is 951,040 acres. The average annual rainfall over this great area of 3,300,000 acres is estimated at from 25 to 27 inches. In the dryest year in which rainfall observations have as yet been made, namely, in 1832, the rainfall in the valley of the Thames was 16.1 inch. Thus under the most disadvantageous circumstances we receive from heaven, with in the limits of the Thames watershed, more than fifteen times the

utmost quantity of water required for the resident population. Nor must it be considered that the water, if supplied to the metropolis and large towns, is chemically lost to the country. In a more or less deteriorated shape it reappears. It issues from the drainage of the towns. A very large proportion of it is, indeed, at present conveyed to the sea at Crossness, and the expenses of the ratepayers are needlessly enhanced by the waste, pollution, and subsequent pumping up of a large quantity of valuable stormwater. But the application of the water that is effluent from towns to agricultural purposes, after it has performed the function of the scavenger, is one of the features of the sanitary measures of the day. An impression of the folly and extravagance of the plan of turning storm-water into sewers is becoming daily more widely spread. And in looking forward to the regular supply of a population of which a part is rural, a part suburban, and a part urban, it may fairly be anticipated that absolute waste of water, such as now takes place to so great an extent in the metropolis, may be expected rather to diminish than to increase.

In the exceptionally dry season of 1832, taking the smaller area of 2,300,000 acres above Hampton, we had a rainfall amounting, in round numbers, to four milliards of tons of water. This, as above remarked, is nearly sixteen times the maximum quantity demanded, on the most wasteful scale, for the requirements of a population of five millions of souls. The question that is most important as to this part of the subject is, In what manner can this fifteenth part of the rainfall which is required for the supply of the metropolitan population be most properly retained for their use? The question of cost is, of course, here highly important. But the greatest cost is that of health and of life. It is therefore rather to be sought, in

the first instance, how best to preserve the purity of the supply. As to absolute cheapness, no doubt the old plan of a water-wheel at London Bridge was the best. Old engravings of London show us a water-tower erected by the side of the Thames, while the landward arches on the City side of the venerable structure of London Bridge were occupied by quaint and cumbrous water-wheels. The tidal force was put under contribution. The outfall of the Thames provided the force requisite to pump its own waters for the supply of London citizens. It is certain that we are not likely to revert to the cheapest source of supply - the Thames just above the pool-at all events, until the limpidity of the stream is so restored that salmon may again be seen sporting in the reach now looked down on by the towers of Westminster.

The observation before mentioned of the abundant flow of pure water through the gravel excavation at Walton is highly suggestive with reference to the question of the mode of storing the rainfall. We can tell, or rather we might tell, if proper steps were taken, what is the annual outflow of the Thames. If the Council of the Institution of Civil Engineers, or the Conservators of the Thames, or the Royal Society, or the more actively voluntary Society of Arts, or anyone whose business it is, or whose credit would be improved by the effort, would pay as much attention to our chief river as Mr. Fowler has given to the Nile, we should soon be in possession of definite information on a subject that comes home to every Londoner. As it

is, estimates differ very widely. Mr. Bailey Denton considers that the outflow of the Thames is equal to a rainfall of three inches over the watershed. Mr. Harrison estimates the summer flow of the river at onesixth of the rainfall. The Royal Commissioners of 1869 exactly doubled this estimate. When we find such wide divergencies of

opinion as to a matter that might be so easily ascertained as the annual flow of the river, it is small wonder that the question, how much of the annual rainfall passes off in evaporation, is without even an attempted solution. Measurements of evaporation have indeed been attempted in some cases. But all that the experimenters have had in view has been to ascertain the amount of water vapourised from a given area in a given time. What became of the vapour thus produced; how far it was absorbed by the foliage of plants; how far it returned to the earth in the form of dew; and how far, if it were wafted by the winds from the watershed district in which it arose, it is replaced by the vapour from other districts, or from the surface of the ocean, no one has yet even attempted to guess. But allowing the fullest flow for the Thames that any measurements justify, and allowing for the freest action of evaporation from the surface of the soil, there must yet remain an enormous quantity of the rainfall of the Thames basin that has otherwise to be accounted for. If this be only one-third of the rainfall, it will still be five-fold the supply needed for the wants of the population.

That the portion of the water provided by the rainfall of the district in question, which is neither evaporated nor carried to the sea by the ordinary river channel, makes its way in some fashion to the ocean there can be no doubt; were it otherwise, the country would be waterlogged. The operations of the well-digger and of the borer reveal, it is true, an ample source of subterranean supply. But the irregularity of level at which water is met in different portions of the basin, as well as the difference of level in the same district, and even in the same wells at different seasons, denote that the subterranean store partakes rather of the nature of a river, cr group of

rivers, than of a lake. A study of the superficial nature of the country points to the same conclusion. Over the clay lands, as, for example, in the district drained by the Brent, a few hours' rain, unable to penetrate the impervious soil, takes the form of a flood, and pours down over a broad space of ground into the Thames near Brentford. On the south of the Thames, on the contrary, the watershed districts, drained, or rather indicated, by the Wey, the Mole, and the Wandle, have no visible outlet for the greater part of their rainfall. These rivers seem rather to lose than to gain in volume as they approach the Thames. It is true that after heavy rain land floods cover the low-lying districts of these river valleys, but the rapidity with which these floods fall is by no means to be accounted for by the surface current over the meadows, or by the increased volumes of the streams. On the other hand, at no very great distance beneath the surface, in the green sand, or in the debris filling up the bottom of the valleys, a copious and unfailing supply of the purest water is constantly to be found. Such is the supply of the town of Guildford, pumped from a well sunk only thirty feet below the level of the Wey-unstinted in quantity, and unsurpassed in purity. We have already spoken of the natural fountain which, on the estate of the Duke of Northumberland at Albury, springs from the river-courses of the chalk. All these facts point in the same direction. As to the country north of London, when we have left the chalk and superposed gravels that border the valley of the Colne, and passed the great ridge of high land that stretches from Stanmore to Barnet, the case is somewhat different. Boring for an artesian well has been carried to the depth, we have been told, of 1,200 feet, in the neighbourhood of Camden Town, without obtaining

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the expected supply of water. seems as though this district were unpromising. Perhaps some fault or dislocation connected with the line of the trough of the Thames may cut off the floods that pour from the south. But on the Surrey side of the river, or on the chalk beyond the barrier of which we have spoken, lie the natural feedinggrounds of the London water supply. No human engineering can form such reservoirs. No human art can ensure so constant and so pure a supply. Not even can it be done if we seek the watersheds of Snowdon or of Helvellyn, and emulate the engineering of the Romans in costly aqueducts.

As far, then, as it is competent to form a forecast from our actual knowledge, we think that the improvement that may be expected in either the gas or the water supply of London is to be sought rather in care of detail than in heroic magnitude of effort. In the supply of coal gas, it does not seem probable that any reduction in the price now regarded as fair can be effected. It is by the purification of mineral oils, and by the careful admixture of cool air at the moment of burning, that we think the best hopes are to be formed, either of producing independent lights for domestic or even for public use, or of keeping the gas companies on their best behaviour. It is by the utilisation of the ample supplies of water to be found in and under the chalk that purity, as well as quantity, are to be attained for the metropolitan demand. Slight as these sources of improvement may seem to those who have not studied the subject, it is possible that much may result from their careful developement. And it is at all events certain that it is not until these simple means shall have been tested and exhausted that we can be in a position gravely to entertain any colossal scheme for improving either the illumination or the water supply of London.

F. R. C.