The question of the life of steel pipes versus cast-iron is one which has long been exercising the minds of engineers. As it is not practicable to sit down and wait for the necessary time (which really means the passing of a generation) to elapse to prove beyond a doubt that the former is equal in life to the latter, the next best thing is to show, by what has been accomplished, what can reasonably be expected. There is no doubt that the life of a steel pipe mainly depends upon the coating, and, given a good covering, a steel pipe will, without doubt, equal in life that of cast iron. This coating is composed of a good mixture of Trinidad asphaltum and tar, and has proved to be most efficacious.

Since the Ferguson pipe was invented about eight years ago, the following, among other mains, have been manufactured.

In South Australia : -

8, 12, 31, and 8 miles respectively of pipes ranging from 15 ins. to 26 ins. in diameter, test pressure to 300 lbs.

West Australia: -

350 miles 30 ins. diameter for the Coolgardie water scheme, test pressure to 400 lbs.

New South Wales: -

13 miles 32 ins. diameter, test pressure to 300 lbs.

South Africa: -

12 miles of 21 ins. diameter pipes for the Premier Diamond Mines, tested to the following pressures: 1/4 in. thick to 300, 5/16 in. thick to 350, 3/8 in. thick to 450, 7/16 in. thick to 600 lbs. per square inch;

2 miles 30 ins. diameter by 5/16 in. for Durban Corporation ;

6 miles 30 ins. diameter by 5/16 in. for Durban Corporation.

England and Wales • -

13 miles ranging from 21 ins. to 36 ins. diameter for the

South Staffordshire Mond Gas Company, test pressure to 300 lbs.; 3 1/2 miles of pipes ranging from 21 ins. to 48 ins. diameter for the Western Valleys Sewerage Board ; 1,500 ft. 86 ins. diameter by 1/4 in. for Conway Hydro-Electric Power Main. New Zealand: -

14 miles 24 ins. and 27 ins. diameter for Auckland. India: -

4,350 ft. 24 ins. diameter by 3/16 in. for Benares Municipality ; 3 miles 24 ins. diameter 3/16 in. for Jubbulpore Waterworks ; 1,680 ft. 18, 24, and 33 ins. diameter for Bombay Municipality. The pipes supplied for the South Staffordshire Mond Gas Company are being laid in a part of the country which is the very worst for steel pipes. Besides containing sulphur and other chemical properties, which are most dangerous to the life of steel, the land is subject to subsidences. It was a matter of great concern to the engineer how best to protect the pipes against such enemies, and after much thought and experimenting he decided upon having the pipes coated once with asphaltum, then wrapped carefully round with Hessian or canvas, and afterwards a further coating of asphaltum applied on top of this. The result has been to produce a coating which is of great thickness, and adheres tenaciously to the pipes, and there is no question but it must go far to remove any trace of doubt as to the life of the pipes in this treacherous district.

The following correspondence confirms our contention that the life of wrought-iron pipes is equal to that of cast-iron, so far as this can at present be proved : -

Department of Public Works, Melbourne,

25th February, 1902.

Mr. Mephan Ferguson.

Sir, - With reference to the life of wrought-iron or steel pipes, the fact is that anticipations have been so much exceeded, and dismal prognostications upset, that I am not yet able to fix a period as the limit of their durability.

It now seems almost that, given the conditions - (a) sound, well-selected plates, free from rust; (b) honest workmanship; (c) perfect coating with refined Trinidad asphaltum, or other equally efficacious envelope; (d) care in transit and laying so as to avoid abrasion of coating or the proper treatment of unavoidable abrasions - the life of wrought-iron pipes may equal that of cast-iron.

When I introduced wrought-iron pipes into Australia for water supply purposes, it was on the basis of Californian practice, and notably as carried out by Mr. Schussler, engineer of the Spring Vale (San Francisco) Waterworks, who at that date had nearly twenty years' experience of the system, with the result that whenever opened up the pipes were found to be in as good condition as when laid, and, with an added eighteen years, I am aware that the same condition prevails. Although at first I was rather sceptical as to a very extended life for them, I was able to demonstrate that, from a financial point of view, if wrought-iron pipes continued to be so effective in the Melbourne water supply system for fourteen years, and were then altogether abandoned, there would be an actual monetary gain at the then relative prices for cast iron and wrought iron, which made a difference of over 50 per cent. in favour of the latter.

But eighteen years have now elapsed, and it can be said of our original wrought-iron main, one of 7 miles long and

30 ins. diameter, that, as is also Mr. Schussler's experience in America, it is as sound in every particular as when laid down, and I see no reason why it should not be found as sound fifty years hence. I find that, before giving up the Melbourne water supply in 1890, I laid wrought-iron pipes as follows: -

or say 58 miles. Excepting in the case of a few pipes laid through bad ground in South Melbourne, and in respect of which it was afterwards found that there had been carelessness in handling, there had been a complete absence of failure, and of the whole of them, as of our initial main, it may be said that they continue to be so sound, that no line is afforded from which to predict when they will be otherwise.

I continue to be, I assure you, quite satisfied with my action in successfully combating doubt and opposition to the adoption of wrought iron for large water mains.

Very truly yours, (Sgd.) W. Davidson,

Inspector-General of Public Works, Victoria.

Department of Public Works, Melbourne, diameter would have lost at least 1 in., and more probably 2 ins. of section, from incrustation. The cast-iron branch, which had been connected to this wrought-iron pipe, with its valve, was heavily covered with material adhering to the inner surfaces in the form of nodules, and consisting of oxide of iron and earthy matter attracted to it. This deposit or incrustation is peculiar to all cast-iron pipes, large and small, in the Melbourne water supply system. Its rate of growth is equal to the complete filling up of a 4-in. pipe in from fifteen to eighteen years. The coating of the wrought-iron pipes, as used in the Yan Yean, is now demonstrated as being absolutely impervious to incrustation, the initial effort in which must be from the iron and establishes the impermeability of the Trinidad asphaltum process. Altogether the result is so pleasing to me, although I have now nothing to do with water supply affairs, that I cannot refrain from expressing it to you, who were so closely associated with my first efforts in introducing wrought-iron pipes, and indeed to ask you to share my feelings of satisfaction, and, in doing so, to authorise you to make any use of this note you see fit.

18th May, 1902. Sir, - In extension of my letter dated 25th February, on the subject of the life of wrought-iron pipes, I cannot now help apprising you of the great pleasure and satisfaction I have just received from the inspection of a length of the South Melbourne 24-in. wrought-iron main, the pipes for which, you will remember, you manufactured. The main crosses from Preston reservoir to Brunswick, and thence down the Sydney Road, and via Queen's Bridge into the city of South Melbourne. It is, I think, about 10 miles long. The pipes are of the original pattern of 1/4-in. plate, with longitudinal double-riveted and transverse single-riveted seams in 28-ft. lengths, fitted with spigots and faucets. The M. and M. Board, within the past week or so, made some alterations-in this main on the South Melbourne side of the bridge, which necessitated the cutting out of a length of 24-in. pipe, to which had been attached a cast-iron 12-in. branch, with sluice valve, etc. This is the pipe which I at once took an opportunity of inspecting.

It was laid early in 1887 in ground that is the most unfavourable of any in the Melbourne district to the preservation of ferruginous material. Inside, the pipe is now as if it had just come out of your works, so perfect and japan-like is the coating, and, making allowance for the adhering clay, the same may be said of the outside, excepting that in cutting out rivets (the pipe appears to have been taken out in sections), and in the handling and cartage, portions of the exterior coating have been knocked off. This, for the purpose of my examination, I found to be rather an advantage, as it afforded me a welcome opportunity for examining the plates in several places. These are in perfect order, and considering the absence of change in practically sixteen years of service, I see no reason why the same condition should not prevail for sixteen years longer, or, for the matter of that, for sixty years or longer - indefinitely. Where no change has taken place it is certainly warrantable to assume that, under a continuation of the like conditions, none will take place. Not the least source of my gratification, having first become satisfied as to the stability and certain longevity of this main, is in the splendid condition of the interior of the pipe. Its perimeter is perfect without signs of incrustation, obstruction, or deposit. This is the more remarkable from the fact that, in an equal period, a cast-iron pipe of 24 ins.

Very truly yours, (Sgd.) William Davidson, Inspector-General of Public Works, Victoria.