DUNEDIN GAS WORKS.

Evening Star, Volume III, Issue 780, 4 November 1865, Page 2

DUNEDIN GAS WORKS.

Gas is undoubtedly one of the necessities of modern civilisation, and in more senses than one its absence denotes social darkness, but like railways and other mighty aids of progress, ga3 works are not easily attainable in a young colony. The capital required for their construction is frequently difficult to raise, and when found is often contributed by foreign capitalists. When those locally interested subscribe amongst themselves the large amount of money required for establishing costly works, the of which, and the profit of the undertaking, depend on the permanent prosperity of the locality, it is a healthy sign of social progress. It is no vain boast for Dunedin that it was the first city in New Zealand to be lighted with gas, and it is still more to its credit that the capital required was almost entirely raised by its citizens at a time when the ordinary channels of commercial enterprise held out much greater probabilities of profit. The most striking feature of this establishment, which covers an area of 2 acres, on the borders of the bay, is the retort house, which is a stoae building admirably adapted to the requirements of the city, and measures 65 feet in length, 62 feet in breadth, and 22 feet in height. It contains at present 5 beds of retorts, with 5 in each bed, and are capable of producing from 65,000 to 70,000 cubic feet in 24 hours. Without extension also, the retort house is capable of admitting 45 extra retorts of equal carbonising capacity. The building is surmoxmted by a circular iron roof, and was originally imported by the Melbourne Gas Company for their works. This is only one of the many examples of foresight which Mr Hutchison exhibits in his management of one of the most important branches of our social and domestic industry. This department of the firm is also used as a coal store, and is capable of containing 1200 tons of coals. Until very recently a large proportion of the coke was used for carbonising purposes in the process of manufacture ; but owing to the newly created desire for that article for domestic purposes having exceeded the quantity produced on the works, Mr Hutchison has devised and erected an apparatus whereby tar is introduced at a high pressure into the retort furnaces in a stream not exceeding three-sixteenths of an inch in diameter. The result has been that the heat produced not only more effectually carbonises the coal, but there is a sensible difference in the labor expended. - The public now therefore can be amply supplied with a coke quite equal to anything produced in older countries. The gas generated in the retorts passes to the hydraulic main, which, to use the vernacular of the business, is a seal to prevent the gas returning to the retorts after having once passed off. It then travels from the hydraulic main to the condensers, which are on the atmospheric principle. These are placed on a tank which receives the tar and other ammoniacal compounds that cannot be effectually separated from the gas when the latter is in a state of high temperature. From the condenser the gas passes off into the " purifying house" to be still further cleansed from impurities. There are four purifiers on the dry lime principle, to which a distributing valve is attached. Two or three of these can be worked at one time, and the remainder left for the purpose of being cleaned. The working capability of these purifiers has been estimated at 80,000 cubic feet in 24 hours. In connection with this part of the process of gas manufacture, we ought to congratulate ourselves upon the fact that for purifying purposes, the Oaniaru lime has been pronounced by the manager of the Dunediii Gas Works as the best he has ever met with. Tliis accruiaitioii, viz., good lime —was, at the opening of the works, one greatly to be desired, and we have the satifaction, as colonists, to know that the whole of the Oamaru district is exceedingly productive h\ this, one of the most useful of all minerals.

The "purifying house" measures 35 feet in length, 21 feet in breadth, and 20 feet in height; and its construction in point of ventilation and general arrangement is such as to render it secure from the frequent accidents which occur on works of a similar character in other parts of the world. From the purifying house the gas is conducted underground to the gas-holder. The tank which contains this appliance is 63 feet in diameter, and is built of brick and stone. The construe-

tion of the tank, owing to the nature of the ground in which the sinking is made, must have been an operation presenting almost insurmountable difficulties, and we do not exaggerate when we say that its perfect completion under the direction of Mr Hutchison, was one of the greatest triumphs of the' works. The gasholder is 21 feet deep, and 60 feet in diameter, and is calculated to contain 60,000 feet of gas. It is made of unusually stout iron, thus rendering it suitable for the exposed position in which it is placed. The gas-holder well, in immediate contiguity with it, and which is 25 feet deep, contains the necessary valves and syphona for the control of the supply of gas in the works.

The works generally have been constructed on such a scale that if Dunedin were to become of equal extent and importance with Melbourne or any other city in the Southern hemisphere, no portion of the machinery would be rendered unavailable, and would only require additions to meet the increased demand. This may be regarded as an unusual feature in the establishment of gas works for small cities. At the present time Dunedin contains 220 private consumers of gas, and is supplied with gas for 156 public lamps, and it may be further stated that if many of our principle thoroughfares had the advantage of public lighting, this number would have to be materially increased.