CHRISTCHURCH WATER SUPPLY.

Star (Christchurch), Issue 3656, 30 December 1879, Page 3

CHRISTCHURCH WATER SUPPLY.

TO TJIE EDITOB OF MB STAB. Sib,—l have just read two articles in your paper, of the 18th and 19th respectively, bearing on the water supply question. As I etill take some interost in it and in the welfare of tho citizens, and should be sorry to see them como to a wrong conclusion, will you kindly permit me to point out where I think you are in error in the remarks that you have made. The drift of your observations points to the conclusion that Mr Hubbard is not worth paying much attention, to, on account of some of the statements that he formerly made, and thoir apparently contradictory nature. In your article of the 18th you remark : —" At that time there was a general concurrence of opinion amougst the engineers who had reported'upon the scheme. Mr Hubbard alono stood out; Mr Hubbard alone constituted the disturbing element." If you refer to the report sent in by Thornton and Bull in tho Lyttelton Times of March 8, and again to my letter of April 7, you will find that this was far from being the case. You will find in the first placo that the report sent in by myself and partner differs in a moßt marked manner from those of tha others —in fact, it substantially agrees with Mr Hubbard in the matter of preßßuro, the slight difference thafc exists being afterwards explained, whilst in my letter I distinctly support Mr Hubbard, and give my reasons for so doing. ■' Again you say—" But Mr Hubbard's great strong point of opposition lay in the difficulty of securing the necessary pressure, for fire prevention purposes from the river Waimakariri, and upon this ho was most positive. All tho engineers had he told us omitted the very important matter of the length of the hoso." On referring to Mr Hubbard's letter of April 1 you will find thejo words — " Messrs Thornton and Bull are the only ones who have represented the matter in a proper and practical mannor, namely, by shewing tho heads duo to friction in each case, as they will actually ocour, and as must be provided for whilst consumption is going on." And you will find in our report that we mentioned length of hose with friction. The above therefore is a misquotation. Wifch regard to length of hose you observe for somo reason or other Mr Hubbard has pufc down 200 feet as the length necessary. Now, as Mr Clark has been so often quoted, although not always correctly, with the view of getting his support, I will here quote a remark or two that appeared in the letter that ho sent from England on April 24 last in answer to ono from Mr Hubbard—" For both these purposes undoubtedly a high pressure is required, and it would appear probable that when tho Council were framing this question they had this in mind. Recent experiments in extinguishing fires in this metropolis mado while I was in the Colonios havo shewn that tho head producing tho jet is to tho jet 160:100; if then you add to this 50 feefc as the head consumed in passing the wator through 200 feet of hose, the pressure in Cathedral Fquare would require to be 160 plus 50 = 210." You then go on to speak of the apparent absurdity of an elevation of something liko 288 feet being required only three miles away for tho Heathcote scheme when 'ID is considered sufficient 18 miles distant. To those having a knowledge of the laws that govern tho flow of water in pipes, it only requires to be understood to be seen. The solution of tlie question simply consists in making the diameter of tbe pipe suitable to its head und length, the quantity of water to be discharged being the ruling factur in this consideration. You next remark: —"Why could not Mr Hubbard have told us then, as he tells us now, that to increaso the main to 21-in would satisfactorily overcome the difficulty." If you will refer to fcho memo of instructions givon by the City Council on March 13, you will find that they asked the engineers to givo information on the question of faction and pressure in an 18-in main. Air Hubbard, therofore, in criticising this question, kept within the letter of instructions of the Council by confining his remirks to an 18-inch main. It is true he might have stated at the timo that the difficulty could bo got over by increasing its size, but he was not by auy aeons called upon to do co, especially as ho was not paid for his information, I called attention to thiß point in my letter of April 7, and also in a subsequent one, the date of which I forget, not having a copy by mo. As was pointed out by the Lythllon Times, the Council made the mistake of asking for information on particular points, instead of on tho whole question. It seems hardly fair, therefore, to blame tho engineers for confining thoir remarks to tho matter under discussion. On the contrary, it would be as woll perhaps if it was a habit that was a little oftener indulged in. In your issue of Dec. 19 you. observe, when referring to tho capabilities of the Waimakariri for giving a puro, abundant and selfsupporting scheme with adequate pressure — " The question before the ratepayers hitherto has been —Does the Waimakariri schemo answer satisfactorily all these important conditions, a question now answered by all tho engineers in the affirmative." In answer to this, Mr Clark characterised tbe scheme as an ingenious proposal, and gave it as his opinion that the filtration would be limited to tho sectional area of the cylinders, whilst Mr Dobson has expressed very strong opinions , against tbo scheme, so much so that he refused to report on it. In speaking on tho difference of levels made by the two engineers, you draw a comparison unfavourable to Mr Hubbard on what hardly appears to me sufficient grounds. Mr Hubbard states that, taking Doyne's contour levels, he makes the height 420 ft, and his levels taken with the barometer give him 412 ft. Mr Blackwell states that his birometrical levels give him a height of , 368.75: It does not follow as a matter of , course that Mr Hubbard musfc be wrong, but if anything rather tho opposite, because in , fcho first place levels taken with the spirit- , level (which Mr Doyne's were) are far moro , likely to be correct than any taken with the , baromoter,.and in the next barometrical levels , are never depended upon to give results

aeorer than a few feet,, and ce-tainly very few would pretend to measure a height tb» way to two places of decimals. The very faot of such accuracy being obtained would on the minds of most at once throw a doubt on the correctness of fche w»rk.. In any case,, however, the levels of one gentleman have as much right to, b* taken as correct aj those of tho other. But the question of levels is altogether foreign to the subject, and) had no righfc to be brought into the discussion, except as a sido issue. The two gentlemen were told to accept the distance as being 18 miles, and fche hc : ght ob 400ffc. .. One put himself to considerable trouble to travel outside his instructions and the other did not. Referring to the discharging capabilities of the mains, you state that Mrßlackwe 11 claims to be able to deliver in Christchurch no lesa than 5,530,000 gallons of water in twentyfour hours. I may a3 well hero si at i that, taking Mr Blaokwell's figures, this 5,530,000 is wrong, and I also make a considerable difference. If you will look at fche table in Mr Blackwell's report, you wiil see there is a mistake in the multiplication of tho 1500 gallons per -minute for fire purposes by 570,000. Ifc should bo 2,160,000, and ifc is set down as 2,730,000. The total should therefore bo 4,960,000 inßteadof 5,530,000. But I make the total discharging power of the pipe 5,616,000 in round numbers ; different formula; givo slightly different results. The difference between these quantities would be 656,000. m 5,616,000 inus 4,960,000 = 656.000 There is another Blight mistake that you have made, and the Lyttelton Times did tho samo in Mr Hubbard's quantity, where 31C6 gallons per minute is put down as 4,459,040 in the 24 hours instead of 4,559,040, bufc it is not of much consequence. You observe, sir : — " We propose fco cut tho Gordian knot of these difficulties by a very simple process. Messrs Clark, Dobson and Son, Hiddlestone, Thornton, Walkden, and Blackwell are all agresd that an ample— an abundant— supply of beautiful water, with sufficient pressure to meet the requirements of tho city for all purposes, can bo obtained from tho Waimakariri as proposed by Mr White." I have already shown that Mr Clark held quite an opposite opinion, whilst Mr Thornton (in conjunction with myself) stated in the report of March 6 that thero would bo a very great deficiency in pressure when tho 18in pipe was used. Finally, Sir, you say when all are agreed on the main question, it is quite unnecessary to waste time discussing the differences between two engineers, more especially when one of them has notoriously given expression to extraordinary and inconsistent opinions. And you then proceed to warn the citizens to beware, and call thoir attention to tho absurdity of supposing that it is necessary to have a head of 288 feet three miles away if 400 feet is considered sufficient at a distanco of 18 miles, and on these and other grounds dismiss Mr Hubbard's calculations as being unworthy of consideration. Reasoning from analogy, Sir, you would be almost justified in doubting the correctness of Mr Hubbard's figures, as you have had such ample precedents of the inaccuracies of those of others. But extraordinary as ifc may appear, Mr Hubbard's figures have the singular merit of being correct, neither more nor less. Tho what appears to you apparent inconsistency of their nature is brought about by threo causes — viz., the sizo of tho pipes and their combined length, and the amount of water proposed to be discharged by them. Tho application of their principle to the case in point, independent of any experience of the present writers on the subject, rests upon the testimony, as I have pointed out in tho Lyttelton Times, of some 'of the leading hydraulic engineers in the world. In writing before, Mr Hubbard was dealing with an 18 inch main and varying qualities of water. Ho is now dealing with a 24 inch main. Properly interpreted, there is no inconsistency whatever in his behaviour. Thore is no approach at a lecommendation in his present report of the Waimakariri scheme. He was asked to report, and he has dono so, probably in fcho same spirit that a lawyer would plead againsfc his conscience (if he had one). Had he been asked for a report on tho whole question, and had recommended this scheme in proference to tho Heathcote, then you might with justice have accused him of inconsistency. I am aware that in writing this letter, I lay myself open to the charge of partizanship, but this I cannot help. I believe Mr Hubbard has treated the question in a proper mannor, and I wish the public to have tho ease represented to them as correctly as possible, in order thafc they may judgo clearly of the issues. I trust, Sir, you will pardon me for having troubled you with this long letter, but I am anxious, as I hopo we all are, to sco this matter cleared of the mystery that seems to surround it, when thore is really no oceosion for any at all. — I am, &c, W. J. BULL, C.E. Oamaru, Dec. 23, 1879.