C.—3

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and, if found by assay to contain an appreciable quantity of mineral, is raised to the stamps by a centrifugal pump, and subjected to further stamping, and thence to the graders and vanners as before. Loss is reduced to a minimum by this means, often to only 2 or 3 per cent., and the cost of working by reason of the whole system being practically automatic is often reduced by fully 80 per cent. The cost of working at the mines of the Fiscal Boyal does not exceed 7d. per ton. " Lead-ores from New South Wales can be concentrated by this system at a very low cost, varying with local circumstances, giving products containing 70 per cent, of lead, with 5 per cent, zinc, and 40 per cent, zinc and 5 per cent. lead. The plant referred to at Freiberg treats about 16 tons per hour. It requires 15 cubic feet of water per minute, of which sft. must be clean. The loss of water is about 1-50 cubic metres per hour, but this is no guide to what the loss would be in Australia, where it may be set down at about 22 gallons per ton of ore treated. " C. Luhrig, of Dresden, is the patentee, and has formed a company in London, called the ' Luhrig Coal and Ore-dressing Appliances Limited, 32, Victoria, S.W., London.' This company has sold its coal rights to a big company in America, where there is a good opening, and where a large business will be done. " Abstract of Guarantee. "The» Luhrig Company guarantees under strict penalty: (1) Quantity plant will treat; (2) material and workmanship; (3) cost of treatment per ton; (4) percentage of enrichment of mineral contents; (5) maximum loss in tailings."

In order that the whole system may be thoroughly understood, complete specifications and plans, as lodged in the Patent Office, are herewith annexed. It will be seen that a portion of the machinery used—namely, rolls and screws —have been in use for many years, and the concentrating appliances are a modification of the Frue and Triumph vanners. Any new machine which is purported to save a large percentage of metalliferous ore at a low cost in necessarily greatly inquired after, but it must be remembered that the cost of labour is far more here than in Germany, and the cost of treatment will be increased proportionately. Seeing that one of these plants is to be erected in New Zealand, it will be well to wait to see the results of its work and the cost of working the same in the colonies, together with the terms and conditions under which this company will allow their process to be used. Until we know what royalty is proposed to be charged, the adoption of the system should be held in abeyance. " Specification.—Ore-dressing Machinery. "Improvements in Apparatus for Dressing Ores. " We, Carl Luhrig, of Dresden, Saxony, German Empire, engineer, and John Charles Cunninghame, of 127, St. Vincent Street, Glasgow, Scotland, iron- and coal-master, do hereby declare the nature of our invention for improvements in apparatus for dressing ores, and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement :— " This invention relates to apparatus for treating ores, so as to separate and retain the portions containing valuable minerals, by the operation of a succession of machines, arranged so as to avoid as much as possible manipulation of the material dealt with. The arrangement which is adopted for this purpose is represented by the accompanying drawing, which is a vertical section of a building, with a set of the dressing-plant arranged according to this invention. " The ore to be dressed is raised to the top of the building by means of an elevator or lift A. It is delivered into a hopper B, whence it passes to the stone-breaker, or it may be a set of stonebreakers, C. For feeding the ore from the hoppers B into the breakers Ca reciprocating-pusher D may be employed, this being moved to and .fro by the connecting-rod E from a crank on a slowly revolving wheel F. As the ore passes towards the breakers, the smaller fragments escape downwards through sieves G, to which a jogging motion is imparted by the tappet H. " The ore reduced by the breakers C, together with the smaller fragments from the sieves G, is conveyed by the shoot I into a revolving sizing-drum /, which separates the material according to sizes that passes into shoots X, Xl,K l , K z respectively; thence they are led into three sets of washers L, by which they are concentrated in the usual manner. The concentrated material is at intervals passed from the washers by opening the valves X into drainers N. The water carrying the finest portions of the ore is led by a shoot N* in graders or funnel-shaped boxes P, by which these portions are graded according to their specific gravities and sizes. " The larger fragments which pass through the drum J are delivered on a slowly revolving table B, where the attendants select the valuable pieces, which require no further dressing, and reject useless pieces. The rest, requiring further dressing, passes by a shoot S to a pair of crushingrolls T, whence the fragments pass to a revolving sizing-drum J l . From this the sized materal is passed by the shoots U into the washers L l , to be concentrated, drained, and graded in the same manner as that dealt with by the washers L. " Such of the material from the drum J 1 as requires reduction is led by the shoot D Ito crushingrolls T l , and thence to the sizing-drum J~ a , from which the sized material is led by the shoot V into sets of washers L2,to be concentrated, drained, and graded as above. The material which passes through <7 2 is passed by the shoot V 1 through another pair of crushing-rolls T 2 to a sizing-drum J s , the finer material being led by the shoot W into the graders P and sizing-drum J 4 , while the coarser fragments are fed by the shoot W 1 into the elevator X carrying them to the stamps Y. The sized material from J" 4 is led into the grader P, the products of which are concentrated on washers P. " The overflowing liquid from all the concentrators and graders is passed into the pit Z, where the heavier fragments and particles sink to the bottom, whence they may be raised by the elevator