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subject of water supply. The contrast that existed between the information, or rather want of information, on this subject, in this country and on the Continent, was anything but creditable to us. They owed something to the Ordnance Survey, and they owed much to several gentlemen who had devoted themselves to this subject. It was impossible to touch the subject at all without acknowledging what they owed to Mr. Symons for the information he had collected with regard to the rainfall. That information had been collected, in the first instance, by his unassisted efforts, and afterwards by the efforts of an unpaid and disinterested body of fellow workers, which were an honour to the country, but possibly not so much an honour to the Government that such a duty should be left on the shoulders of private individuals. The Bluebooks which had been issued by the different Commissions contained a mass of information, and so did the proceedings of the Institution of Civil Engineers. But when they turned to other countries, a very different state of things was to be found. The Italian Government published, in a form accessible at a small cost to every landowner, information as to the flow, both in summer and winter, and all the other particulars of every river in Italy. But if we turned to our own books and proceedings, there was an absolute absence of this fluviometric information which in Italy was at the command of everybody. He need not point out how important it was to the engineer and landowner, or to any one who had to keep off floods, or seek for water, to possess all this information ; and therefore it was not merely as an academical demand, but as a matter of practice, that this knowledge was required. Many of them were aware of the present condition of the Thames, and he apprehended, from instructions recently given by the Board of Trade, that they would shortly be in possession of the actual summer flow of the Thames during July. The lowest account of the flow was that of Mr. Harrison, who put it at 309 million gallons per day. Mr. Bateman put it at 350 million gallons as the summer flow, for days and days together. But the question was whether, with a long series of dry years which might naturally be expected to follow the long series of wet years we had had, a constant supply of 350 million gallons could be anticipated. On the other hand the demand was constantly increasing. The quantity pumped in July, last year, by the five metropolitan water companies, exceeded 75 million gallons per day; and considering that in the Valley of the Thames, not including that of the Medway, there were now something like seven millions of inhabitants, who require 225 million gallons a day, that was making an unpleasant approach to the 350 millions of possible flow. In forty or fifty years, those seven millions would have increased to something like 14 millions, and the 225 million gallons required now would be from 400 to 500 millions. It was tolerably clear, therefore, that it was desirable to know all that was to be known about the sources and the behaviour of the Thames.
With regard to dummy wells, it was a local question how far any individual well might absorb a flood, but as to the general idea, he thought all would agree it was a feasible and good one. There was one point to which he would call the attention of practical men which had not yet been touched upon. The Valley of the Thames and Medway included an area of something like 6000 square miles, or 5000 for the Valley of the Thames alone, and of this, according to the figures, something like 4000 miles was a permeable area, of which 2000 were chalk and 2000 miles sand and gravel-a true water-bearing area. The great object of the Geological Survey was to avoid wasting flood-water. The natural storage of this water was the pervious waterbearing beds, and the importance of the information suggested as to the percolation from the surface was no doubt very great. They had the facts of the rainfall, and of course they could get nothing more than the rainfall. About fifteen inches evaporated in the course of the year, which would leave only eleven inches to be dealt with in the Thames Valley, of which it was supposed two or three
ran down the river Thames. But in whatever mode the water got into the water-bearing strata, there was no doubt it escaped from it very irregularly. It escaped at the lowest lip of the basin, and if a thorough knowledge of the basin were obtained, it occurred to him it would be possible to raise the lip, and place a regulating sluice there, and by that means, to store one, two, or three years' of rainfall in these water-bearing strata, to be drawn upon as required and so keep up the flow of the Thames.
Mr. BALDWIN LATHAM said, with reference to the escape of water from the outcrop of the chalk formation, it was quite clear that all round the escarpment of the North Downs a very small quantity flowed away in the opposite direction to the dip of the strata, which was towards London ; in fact, immediately under the chalk there was the upper greensand, which all along the escarpments was worked, at various quarries, both for building and fire-stone ; and the level of the water in those quarries varied with the level of the water in the overlying chalk formation; and although there appeared to be the chalk marl intervening between the upper greensand and the chalk, he did not think it was of such an impervious nature as to prevent direct communication between the waters of the two strata. In fact, it was clearly shown where the chalk marl came to the surface all along the foot of the escarpments of the North Downs, there were no ditches or streams all along the formation, and all the rain equally disappeared there as it did over the chalk itself; therefore, practically for all water supply purposes, the chalk, with the chalk marl and upper greensand, might be taken as one stratum. There were immense fluctuations in the quantity which was stored from year to year in these formations. In March, 1883, they had one of the largest quantities of water stored in the chalk of the North Downs and South Downs which had been known for many years, and yet at the end of 1883 they had one of the lowest water periods. That was a thing which had hardly ever occurred beforegoing from extreme high water to extreme low water in a VOL. VIII.-H, C.
single year. The maximum probably exceeded the minimum by ten times, and, therefore, when considering the water supply of a particular district, the minimum must be borne in mind, and either the average or the total capacity, seeing there were these immense fluctuations in the quantity of water which were common to all geological formations. The same thing occurred in the new red sandstone, the permian beds, and the oolite, in all of which he had carried on observations for some years. It was absolutely certain, therefore, as Mr. Lucas had pointed out, that a future water supply for underground sources must depend upon correct hydrogeological surveys. When the quantity of water was known, and they could show the yield over certain years, and what area of strata was required to supply a definite quantity of water, there would be nothing to do but to make careful observations in order to get a sufficient supply of water. The question of compensation would naturally crop up, and to his mind there was not the slightest doubt that a single drop of water could not be taken from any of these porous strata without interfering with the flow in some adjoining stream. It seemed, therefore, to be a matter of great injustice that power should be given to water companies to sink wells and abstract water to the injury of those who had property, and often very valuable property, in the water supply, without compensation. The hydrogeological experiments which had been made would tend to show that these areas which were affected contributed their supplies to different rivers, and when it was essential to the public advantage that supplies of water of this character should be procured, it was only right that those who were injured should be properly compensated. With reference to Mr. De Rance's proposition as to the means of storing water in porous strata, of course there were great difficulties in the case of elevated strata, but there were other circumstances in which water might be stored in that way. In the course of his investigations, he had received the most valuable contributions from General Hyde, of the
Indian Railways Department, who stated that in Peshawur, from time immemorial, it had been the practice in the rainy season for the natives to cut channels from the water source to the wells so as to fill up the gravelly strata underneath the more impervious surface stratum, and when the wells were filled in that way they were closed, and only opened in the summer time, so that they had at that period an abundant supply of water which had been cooled by coming in contact with the earth at the time at which it was stored. Therefore, what might appear to be a new idea, was really one of extreme antiquity. The whole question of water supply was one of the greatest importance with regard to the public health, and it behoved them, especially in seeking for these underground supplies of water, to take care that they were sought for at points not liable to contamination. Many underground sources of water supply were polluted to a frightful extent; and really the cause of his undertaking these investigations was the repeated outbreaks of typhoid fever in the district with which he was especially connected. Having been able to collect statistics for some fifty years back, he could say with confidence that there was the most marked parallelism between the state of the underground water and typhoid fever. Not only so, but these statistics showed very clearly that there appeared to be a ten years' periodicity in low water times. One of the lowest water periods in this country occurred in the cholera year of 1854; another very low water period occurred in 1864, and another in 1874 ; and two years ago he predicted, as the result of investigations, that there would be a low water period this year. There was not a shadow of doubt in his mind that over a large portion of England we should have the water lower this year than it had been for years, and the consequence would be that the diseases which followed those periods were likely to be more rife than they had been for some time past.
Mr. W. SMARTT said he understood that the water at Birkenhead was contaminated in a very serious manner, and