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A BIG BORE., Issue 7983, 12 August 1889
A BIG BORE.
Not the common, every day, time-wasting bore who exasperates his friends by inopportune button-holing at street corners, nor the conscienceless variety of bore who loiters in the wake of an acquaintance that is steering for the refreshment-bar, It is of a different kind of bore that we would say a few words: a bore that will neither afflict nor annoy : a bore with a purpose: a bore that we want j a bore, in ihort, for water. The New Zealand Refrigerating Company must have a regular and abundant supply of water at their Burnside works, and to obtain thin they have covenanted with Mr. J. H. Stubba to put down an Bin pipe to a depth of I,oooft. This is no light undertaking. Many men can bo found willing and competent to drill to the depth of three or four hundred feet, but the difficulties from about that point increase at an enormous rate, and it requires the skill of an expert to sink lower at a profit. Mr Stubbs, though brought up to a very different line of business, has for years paßt made a special study of the most approved methods of making deep borings, and, having operated with succees in the petroleum district of Poverty Bay, was asked to give a price for the present contract, whiph will be the bjggest undertaking of the kind ever seen in these parts. He has his plant already on the ground ; the derrick is completed by Messrs Crawford and Watson, who have, we are told, made a capital job of it; and it is expected that the boring will be begun on Wednesday. It Bhould be an interesting sight to watch the drill at work. We do not propose to weary the casual reader with a full description of the apppliances and the manner of working, but may mention a few facts to give some idea of the process. The derrick, erected straight over the place where the perforation is to be made, is 75ft high and 20ft square at the base, built of sawn timber and bolted together in euch a way that the parts may be afterwards 'taken asunder and the concern re-erected in another place. At the top of this derrick is a pulley, over which bangs a ropo, one end of which is attached to the boring tools and the other end connected with a beam engine. The tools are thus raised and dropped, and it is this raising and dropping that makes the hole and ensures its perpendicularity. With ordinary care in operating, the drill must be straight up and down so long as gravitation is a force. It may sound strange to say that the hole is made with a rope instead of with rods, but the reasonableness of the process is manifest to anyone who gives thought to the subject The appliances are calculated to drill to' the lowest-tested depths—Mr Stubbs would, if necessary, undertake to go down 5,000 ft; and in thus penetrating the strata there comes a depth at'which rods would not bear their own weight. The weight of a full set of tools, it may be mentioned, is about a ton and a-ha]f, and in upright measurement they are as 46ft of solid iron and steel. The engine used for the purpose was specially made in America, and, though plain in appearance, it has connected with it over twenty-five patents, the main principle being that an irregular stroke is produced, the operators relying on the steam in the cylinder to give a free blow. TE'e strokes are to be thirty-five per minute. The engine lifts the tools about 2ft at each stroke, but this stroke is added to by the spring of the rope. We have said above that one end of this rope is attached to the machinery on the surface. This is not strictly correct. If it were, there would be no downward progress; the tools would hit nothing after a few strokes. The arrangement is this : that the machinery grips the 'rope on the bight, and by an ingenious contrivance the man at the top can increase the length of rope in the hole, lowering it by a quarter of an inch at the time. This man, as it were, feels his way with the tools, and by constant practice knows exactly what length of rope is required. The instrument that does the cutting—that is, the lowermost of the tools —is simply a piece of iron with a sharpened point as broad or a trifle broader than the diameter of the hole to' be bored. It is kept turning round, like a gad, and simply pounds away at the bottom, the stuff being brought up in the shape of mud by a sand pump. A clearance is made every four or five feet. Mr Stubba says that he does not mind how hard the stuff is on which he has to operate—whatever it is, it is bound to come away—and he would sooner drill on granite than on soft substances, as these are apt to choke the tools nnless care is exercised. To guard against the loss of a set of tools by accident, another set appliances is kept handy to fish up anything that becomes disconnected. The rope used is 6in cable-laid manila. It is expected that when the work is in full swing the boring will be proceeded with at the rate of 30ft or 40ft per day of twenty-four hours, and if anything like a good Btream of water is found it should yield from 700,000 to 1,000,000 gallons per day. The preliminary investigations as to the lay of the country and the geological formation were undertaken by Sir James Hector.
A BIG BORE., Issue 7983, 12 August 1889
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