1. Chairman.] WILL you be good enough to place the Committee in possession T. Hawksley, Esq. of the objects, that you sought by the plan for purifying the Serpentine, which is

now in operation, and also the means by which you expect to attain it. First of 5 March 1860. all, I ask you whether you were consulted by the late First Commissioner of Works, and were you consulted upon the special point as to the waters of the Serpentine, or was the whole question laid before you?—It was with respect to the purification of the water of the Serpentine. It was at the same time explained by the First Commissioner to me that he saw no possibility, and that he could not propose to the House of Commons to take a vote for the large sum that would have to be expended in altering the bottom of the river.

2. What did you consider to be the defect in the Serpentine that you had to provide against-The First Commissioner sent to me for the purpose of proposing to me to make an examination of the state of the water of the Serpentine; and he desired that my opinion should be given to him, as the termination of the Session was approaching, in as short a time as possible. I told him that there were some difficulties arising from want of information, as there would be a considerable amount of data to get up; and particularly as to soundings and things of that kind. He then mentioned to me that he would furnish those particulars from the office; that he thought they had everything of that sort in the office, and he would direct that I should be supplied with them. In the course of a couple of days after that I was supplied with them, and I immediately proceeded to make a personal investigation of the state of the water of the Serpentine, and the results are given in the report that was, I believe, presented to The House. With regard to the date on which I received the information from Mr. Bonham Carter that Mr. Fitzroy desired to see me, it was on the 7th of July. The papers reached me on the 9th of July.

3. When did you send in your report ?-The draft report was sent in on the 15th; it was sent in in the first instance in draft, for the purpose of ascertaining whether it contained every thing that the First Commissioner required, and it did; it was returned to me on the 19th, and was fair copied, and sent to the Board on the 20th.

4. Are the Committee to infer from this report, in which you treat the green flocculent matter in the water as the chief evil, that you do not consider it neces

5 March 1860.

T. Hawksley, Esq. sary that the mud should be covered over or removed in order to purify the water? -So far as the purity of the water goes, it has, certainly, no effect upon the water, as you can ascertain both by the appearance and taste, and by chemical analysis; the quantity of organic matter held in solution, by the water of the Serpentine, is remarkably small, and not more than it is usual to find in the Thames above the tidal influence, so that the quantity is very small indeed, it is only a little over two grains in a gallon. With regard to the salts, the mere saline matter held in solution is almost precisely the same as in the ordinary Thames water.

5. Have you had any analysis made, in addition to that which you have alluded to from Mr. Spencer-No, I have not since been called upon to make any.

6. Are the Committee to infer from your report, that the question of preventing danger to bathers and skaters from the depth of the river, and by the inequality of its bed, was one which might be tried, independently of your plan for purifying the water?-Quite so; it was reserved; and you will find, I think, if I do not imperfectly recollect, a spontaneous note at the end of my report, which arose out of some conversation that I had, for I had many with the First Commissioner, and that induced me to put at the end of it a spontaneous note on that subject; although I was engaged to purify the water of the Serpentine, I was desirous also to mention that i had not failed to consider the other matter, so far as it had been incidentally mentioned.

7. Did this note that you added, allude to the danger throughout the whole of the water, or only to that part of it which is near the edge, and which is frequented by bathers who are not strong swimmers ?—It related to all the water excepting that part of it above the bridge which is extremely shallow, and where no bathers are at present, although possibly it might be well to alter that regulation, allowed to go. In consequence of the sewage mud which has been deposited there from the occasional overflowings of the Ranelagh sewer, that part of it has not been in a very fit state for bathing.

8. Will you now proceed to explain to the Committee your plan?-1 examined the water of the Serpentine in many parts, not merely at the side, but upon various occasions I took a boat and went upon it, and I may say that the First Commissioner on two occasions met me there, and he also accompanied me in the examination of the water in the centre of the Serpentine as well as elsewhere; and the conclusion that I came to, from having had a long experience in these matters, and also from the result of chemical analysis was this, that the lake was abundantly large to keep the water pure by the simple process of natural oxydisation which takes place in all large lakes, although it does not in small ones. I found by the results of analysis that it was almost perfectly pure; but I found that it was very much loaded with filaments of confervæ, and with the lower orders of vegetation, such as naviculæ, and other matters of that kind. And therefore I was induced to try a very simple experiment, that is to say, whether I could, as I expected to do, and as I had done in many other cases, strain this off. I found that I could, and that straining left the water perfectly clear and transparent-good in every respect-as good as Thames water in every respect.

9. When you speak of the Thames water, do you mean the Thames water in London?-No; I scarcely call that Thames water.

10. Above the tidal area?--Yes; I mean that it was practically as good as the water which is supplied by the companies after filtration from the upper reaches of the Thames, that it contained an excess of not more than about a grain of organic matter in a gallon.

11. You consider that the water which is now stagnant in the Serpentine is as chemically pure as the water which is delivered by the water companies after filtration With a little difference, as I tell you, about a grain in a gallon.

12. Then what feature in the water do you think it was that required the expensive process which you have recommended?-With the exception of perhaps, rather demurring to the word expensive, I may say that the matter which I wished to take away was all the organic matter that was not in solution, and as I mentioned before, it consists of fibrous confervoidal plants and small naviculæ, almost microscopic, and many of them quite microscopic, and other plants of the very lowest order, which usually, in these cases, give to water that green tint which may be perceived in other reservoirs under similar circumstances. They are very common; we know all about them; they have been well investigated; we know under what circumstances they occur, and how to remove them.

13. Did

13. Did you find that this vegetable aquatic growth pervades the whole of the T. Hawksley, Esq. water from the bottom of the bed to the surface?-It is dispersed through the whole of the water, of course; it grows most upon the margin where it is more 5 March 1860. directly exposed to the agency of light and heat. If you could make the water much deeper than it is you would have nothing of it, except on the margins; and if it were much shallower, then you would have a great deal more of it. In the reservoirs for waterworks, where the water is pumped in in the brightest possible state from a well, these things make their appearance with most extraordinary rapidity. At the Liverpool reservoir, and I can give a vast number of instances, the water could not be kept a fortnight, although it was pumped from deep wells out of the sandstone rock; chalk water acts in the same way; chalk water produces these things with such extraordinary rapidity, that a reservoir filled with that water will in a few days become loaded with these things; and hence it is that we are obliged, where the waters are used for the supply of a town, to arch the reservoirs, and earth them over. I have vaulted over a great number.

14. So that the purest hard water which contains much carbonic acid gas will, when exposed to light and heat produce much of this aquatic vegetation without there being any impurity in the water itself?—Yes; particularly where it contains a considerable amount of earthy neutral salts, such as lime and magnesia.

15. Are the Committee to understand that the object you set your mind to was to extract from pure water a great mass of aquatic vegetation?-No, I did not set my mind to that in that particular way. What I investigated was first how the end to be sought for could be attained in the most effectual manner, and with the greatest economy, and I found that it could be attained in the most effectual manner, and with the greatest economy by establishing these filters because you could purify by these filters very much larger quantities of water than you could purify by any other means. If you can take two millions of gallons through these filters in hot weather, you get rid of the suspended matter in two millions of gallons of the contents of the Serpentine every day. If you could put one million of gallons of fresh water into it, that one million being as liable, and more so, to produce this kind of vegetation, you would do only half the work.

16. I wish to know whether as you are satisfied that the water is as pure as the water which is drunk by the people of London, the object was not somehow or other to get rid of the confervæ, the diatomacea, and other vegetable growth-Quite so; having first ascertained that there was no noxious matter held in solution-that first attracted my attention. Water may be sometimes very clear, and at the same time very much loaded with matter in solution, and knowing that, and having had very much experience in that matter, I first directed my attention to that subject, and I found that it was not so.

17. There being so much vegetation in the water as to make it quite green to the eye, how much of this vegetation do you expect will be deposited as scum upon your filters ?-Practically, the whole; every part of it.

18. Have you made any calculation as to the amount that may be daily deposited out of your million gallons which pass through the filters?-In weight it really amounts to nothing; there is no mud in the water; it is only these small organized matters. I could not give the quantity, it is so small; suppose I estimated it at a grain in a gallon, a seventy-thousandth part, that would be nothing. What we find in filtering is this, that there is a coating left on the surface of the sand; it does not sensibly penetrate the sand, not a quarter of an inch; and then the filtration gradually diminishes in the rate at which it allows the water to pass through. When it is thought to be sufficiently plugged at the top, the water is allowed to fall away from the surface of the sand by the operation of a valve underneath; and then an instrument is applied, a mere shovel or scraper, by which about three-eighths of an inch of the sand and the whole of this vegetable coating are removed, and that is taken into any convenient place. Here it is taken within this building (pointing to a drawing), where it is instantly washed, and the clean sand brought back again and spread over the surface of the filter bed. The whole of the cleaning would take from two hours to three hours, and the whole quantity to be removed from the filter bed of this area (pointing to a drawing) would be about six cubic yards of sand.

19. Although you could not form any estimate of the weight of so light a material as the filaments of the confervæ, have you made a calculation as to the extent that would be covered by it in a certain period of time. For instance,

5 March 1860.

T. Hawksley, Esq. what quantity of water would have to pass through the sand at the filter before that filter would be stopped up by the deposit of vegetable scum ?-It varies at all periods of the year. When the water is very bright, for these things grow most under the stimulating action of light, the whole four would require to be cleansed once in about three weeks; in the very worst circumstances, in about a fortnight; but that must be under extraordinary circumstances.

20. The whole four would require to be cleansed once in three weeks ?—No, not if you take the whole year round.

21. During the summer?-Yes, but it would be done between the hours of five o'clock and eight in the morning, and it produces no nuisance. The sand is taken out and carried into this building (pointing to the drawing). The water passes through the sand and removes all these filamentous matters almost instantly, and then runs into the sewer; there is already constructed a communication for that purpose; there is nothing to be carted away from, and nothing to be carted to, the place.

22. You do not propose that these vegetable matters should be exposed to the air, but that it shall be immediately cast into the sewer?-Certainly; it runs spontaneously into the sewer as the water comes through the bottom of the vessel containing the fouled sand, and it rises through and brings the dirt with it, all these filamentous matters: the water overflows the top of the vessel in a dirtied state, and carries the deposited matter away with it; it is carried into the sewer and it leaves the clean sand behind; that is the ordinary and constant operation in these cases.

23. What sewer is that?-That is the Ranelagh sewer, the Uxbridge-road

sewer.

24. Have you made any calculation as to the amount of labour involved by cleansing the filter beds?—It is so small that I scarcely know what it is; it is that of only three or four men who are called in for just that time in a morning. filtration-The

25. Will you state what you intend to employ as a medium of filtration -The medium of filtration is washed sand which reposes on different sizes of gravel, beginning with the very small shingle at the top, so small that it will not allow the sand to pass through it, and that enlarging again so as not to allow the stratum incumbent upon it to pass through, and so on until it arrives at stones as large as this inkstand. The water goes down through this, and then passes into drains at the bottom, and so flows away to this large fountain (pointing to the same) and falls over that in a cascade into the Serpentine; it enters from the engine at this fountain (pointing to the same) and is distributed into all these filter beds, and then sinks to the bottom and makes its way to this circular fountain (pointing to the same) and then tumbles over into the Serpentine.

26. These filters would only, I presume, remove matters in suspension, and would have no effect upon anything that was held in solution in the water ?-It has a little effect, but nothing that is very material. This is the mode in which the operation is performed: this is an empty filter bed (explaining to the Committee by a drawing). This is the filtering stratum of sand, and the shingle and gravel are represented in succession; this upper portion is sand; above that is water; below that is shingle; the water is then collected by lateral drains, into one large central drain, and it rises up in this pipe (pointing to the same), passes along that pipe, and then makes its way along the pipes laid down here to this part (pointing to the drawing). This is the work as designed, and as now constructed-(A drawing being exhibited to the Committee). The engines are placed in that central building, and the house with the side doors contains a sort of washing cistern; the water comes from the engines into this central fountain; it then disperses itself in every direction, generally into the whole of these filter beds, except during the time of cleansing, a short period, when one will be let off. It passes into these filter beds, and then comes along here (pointing to the drawing), where there is a pipe concealed under the ground, and comes to this fountain, where it falls over into the Serpentine.

27. What amount of water has to pass through the filter beds?-Two millions of gallons per diem; 1,400 gallons per minute, besides the supply to the jets. There are two fountains, and the water from the filter beds falis over this (pointing to the drawing). This is a fountain 16 feet in diameter. There is another system worked by the same engines and the same operation, which elevates the purified water into some cisterns which are placed in the roof, and that purified water supplies all the jets of the fountains.

28. Will

28. Will you state now how the water is drawn from the lower end of the T. Hawksley, Esq, Serpentine, and brought to that point which you have explained?—The water is taken from the lower end of the Serpentine by means of a brick conduit, and that brick conduit is laid at the necessary inclination, to convey something more, I think, than 2,000 gallons per minute, and it carries it directly into the engine-room.

29. What is the depth of the lower part of the Serpentine from whence the water is drawn?-I think it is 11 feet in mud, and eight feet in water.

30. At what level is the entrance to this conduit?-The entrance to the conduit is brought as near to the surface as is necessary to keep it submerged, so that it will flow with its full volume; but the water can be drawn from any depth.

31. Will you explain that on the plan; the conduit seems to be very near the ordinary level of the upper surface of the water; the entrance of the conduit is near to the top of the water-Yes, and purposely made so.

32. Can it be drawn from any level?—Yes, in exactly the same way that the water is brought up again. There is nothing to be done but to turn the pipe downwards, and the water will rise up that pipe so long as all the pipe is submerged, and it will enable the water to be drawn from any depth-from the bottom, the middle, or the top, just as you please.

33. You would continue the pipe from this conduit?—No, I would not, because it is not objectionable to do so. The largest quantities of this matter, of which I spoke, are to be found near the surface, and therefore the faster we can draw it from the surface, the more we shall carry away; it will be replaced from the water below.. 34. But what would become of the vegetation below the level where you were drawing?-You cannot skim water off the surface only. It is always being mixed by the difference of its temperature, and as the water is never lying in strata, I could not skim off the surface water; that is impossible.

35. I ask you whether the filaments of the confervæ which are at present near the bottom would rise and enter this conduit to be drawn into the filter beds ?-Certainly; as I mentioned, by merely putting an iron pipe in for this purpose you may draw from any depth, we do it in reservoirs frequently, and put three or four valves on for that purpose.

36. Do you anticipate that there would be a current of water upwards from the bottom ?—No; not a current, in the sense of a visible stream, but all the water is being continually mixed, you cannot keep one part stagnant under another.

37. I particularly allude to those things which are held mechanically in suspension, would they be moved upwards by the water, so as to enter it. What guarantee is there that much of this vegetable matter will not always remain beneath the influence of the conduit which is placed at the level of the water?— Because this vegetable matter is to be found chiefly at the surface, and it is continually rising to the surface, and is always rising in hot weather, that we see in all cases of waterworks, reservoirs-there is great difficulty in consequence of that circumstance in keeping the surface of such reservoirs clean.

38. With regard to the matter which does not rise; how would that be carried off by the conduit? That which does not rise is fixed.

39. I mean that which is floating on the bottom of the water?-That will always rise; it is always changing its place, and coming to the surface, particle by particle in succession.

40. Will you just explain the action of the engine in drawing this water; how is it drawn from one end of the conduit to the other. In other words, when your steam-engine is drawing the water through this conduit, does it keep the conduit always full, with a perpetual stream, or do you anticipate that only part of the conduit will be filled?-The conduit will be filled, and the water will be drawn in the requisite quantity, as the conduit is made larger than necessary to supply the exact quantity of water which is required to supply the system of filter beds. It commences below the surface of the water, and consequently, the conduit will always be full.

41. What is the size of the conduit?-It is 30 inches in diameter, and the water is brought into this well (pointing to a drawing), and these are the pumps which receive it from the well. This is the top water of the Serpentine, and that will be the level of the water in the well when the engine will be at work (explaining to the Committee by a drawing), the difference being the head which is necessary to give a velocity to the water along the conduit.

42. The fall on the plan is marked as one inch in 100 yards?—Yes; the diameter of the conduit is calculated to that fall.

5 March 1860,