volume of blast with a Root's Blower is said to be 50 per cent. less than with a Fan. There are upwards of 800 of Root's Blowers in operation in the United Kingdom, and a much larger number are at work in the United States and on the Continent; and they are employed for the following purposes:-supplying blast for Danks's patent Rotary and other Puddling Furnaces, Refineries, melting metal for Bessemer Converters, Iron Foundries, Iron Ship-building, Smiths' Shops, Copper and Tin Smelting, Chemical Works, Distilleries, Rice Mills; Ventilating Mills, Ships, &c.; Wool-drying, Calico-drying after printing, Flour Exhausting in Corn Mills, Meat Preserving, &c.

The construction of the machine is shewn in Fig. 2, which is a transverse section.

The casing of the machine is bored out, and the end-plates are accurately planed. The centre journals are bushed with long gun-metal bearings; and the shafts are Bessemer steel. Special machinery is employed in the manufacture of the Blowers, and all parts are worked to standard templates, and are interchangeable. This Blower is equally effective in exhausting as well as forcing air; and this machine has been found to be a perfect Mine Ventilator.

THE BEST MINING MACHINERY.

BY RALPH GOLDSWORTHY.

I am induced to write this Essay, knowing that interchange of opinion and discussion of such an important topic as this will benefit the competitors, and, generally, all connected with mining.

ENGINES.

Well, then the best mining machinery is not always the most modern, as we have sufficient proof in the good old type of engine, the SINGLE ACTING CORNISH PUMPING ENGINE, which is not equalled by any of the new forms now developed. Although the duty is said to be dropped off, this is not really the case, the difference of duty now as compared with forty years ago will be found to be owing to the inferior coal now used, as may be verified by the agents' reports in most of our great mines, more especially during the last winter months when coal was so scarce.

If a mine is intended to be permanent, the first requirement in opening up will be to provide for its efficient drainage, and to effect this in the most economical way must be to use the Cornish Single Acting Pumping Engine, which engine is universally employed in the Cornish Mines, very largely in foreign and continental mines, and is now pumping nearly the whole of the water supply to the inhabitants of London. From the time when Trevithick first took his engines to Cerro de Pasco, in 1816, erected and set them to work on top of the Andes, and successfully drained the celebrated mines which are again recently

set to work, still employing the same type of Engine (which has been constructed in parts sufficiently light for carrying on mules' backs to an altitude of about 15,000 feet, a triumph of engineering skill, and the greatest mining enterprise of its kind on record); from that time to the present no machine has been built that can equal the duty now being obtained from the Cornish Engine in our most successful mining enterprises at home or abroad. On visiting the Grand Junction Water Works, Kew Bridge, London, I saw one of the noblest pieces of mechanism now in use—an engine with 100 inch cylinder, 11 feet stroke, equal beam, pumping 6,400 gallons of water per minute to a height of 175 feet, on 21 lbs. of coal per horse power per hour, working without the least shock, vibration, or noise, and this gigantic machine was so completely self-acting that it was entirely under the control of one attendant; engines of the largest size ever constructed on this principle require but one man's attention. The engine by its side, is a 90 inch cylinder of same class or type as are all the others in this colossal establishment, and does a duty of 105,000,000 lbs. lifted one foot high by 1 cwt. of coal ( best coal), as quoted by Mr. A. Frazer, in a paper read before the Society of Engineers, but with the common dust coal now in use in London its every day duty is 90,000,000. All the engines here employed are of the Cornish single acting type, and a visit to these works will amply repay any mine agent, mining expert, or the most qualified engineer.

The largest machine in the world for pumping water is that employed for the drainage of the Haarlem Lake, in Holland, which covers 45,230 acres at a depth of 14 feet, or containing a sufficient quantity of water to supply the inhabitants of London from six to seven years; the cylinders are 12 feet diameter, working eleven pumps each 63 inches diameter, and 10 feet stroke, each pump lifting 6 tons of water per stroke, and doing a duty of 90,000,000 lbs. raised 1 foot high with 1 cwt. of coals, or 2 lbs. per horse power per hour, a duty

certainly not attained by the rotary engine, in the best conducted mines or works; these colossal engines and machinery were manufactured, erected, and set to work by the celebrated engineers, Harvey & Co., Hayle, Cornwall.

Now as the question of fuel is of the first importance in establishing a permanent mine, the description of engine to be employed must involve the careful consideration of the engineer: in the first place it is usual to learn what is being done in the best practice, and for this purpose I annex, in Tables I and II, some data of engines I have visited in London and the County of Cornwall during my summer excursions.

Mr. Warrington Smyth has said in his lectures that he has watched a large pumping engine, in the North of England, raising water 105 fms. in 12in. lifts, seven and half strokes per minute, consuming 25 tons of small coal per day. Now this amount of work is done in Cornwall, with less than 2 tons per day, as is shewn by the Tables.

No doubt a visitor to any of the above establishments in London will meet with the same courtesy that has been extended to myself; and, after an inspection of the above the unprejudiced engineer will have no hesitation as to which type of engine it is preferable to adopt.

BULL ENGINES.-The direct acting Bull Engine is now coming into more extended use in the Northern Mining districts. The piston is directly attached to the pump rods, and the whole machine supported on framework over the pit or shaft. Its advantages are compactness (probably three bull engines might be erected in the same area as one beam engine of the same power) and less first cost in engines and buildings; but, on the whole the duty obtained has not been quite so great as in the beam engine, and where first cost is not of so much importance as permanence and high duty, the single-acting beam-engine must be recommended for its high degree of expansion, isolation of

steam passages and piston cover from the cooling effects of the condenser, great speed of piston, and small amount of steam lost in the steam passage. It also has the advantage of leaving the mouth of the shaft free for ventilation, or other purposes.

The Cornish single-acting engine may not be recommended for small powers-say 30 h.p.-but I prefer the beam engine, with the common reciprocating plunger pump, rather than the horizontal type of engine in this case also; and, as economy in first cost of works is generally considered, I say this type of engine can be rendered equally cheap. The pillars, entablature, framing, &c., must be self-contained, and should be made of sufficient strength to increase the power of the engine from time to time, as the sinking of the shaft progresses; and, when the requirements of the mine are greater, a new cylinder and pump may be added at a cheap rate, and a few hours stoppage of the engine should suffice to put them in place, if the design is properly arranged.

QUICK AND SAMPSON'S PATENT PISTONS.-Numbers of these engines have in use, Quick and Sampson's patent pistons and Husband's patent four-beat pump valves and seats; and I think I cannot do better here than quote from the manufacturers' descriptive circular :

"It is a well known fact that the present pistons of steam engines produce enormous friction, rapid wear in the cylinder, more especially when first packed, and produce the same friction whether loaded heavy or light, the work of compressing the packing or screwing down being always unsatisfactory; there is no sure indication of the amount of pressure put on, and, oftentimes, it is packed so tightly that a tremendous pressure of steam is put on to move it. In the case of springs used in superheated steam, they readily lose their elasticity, and are consequently useless; they produce undue friction when first put in, and the piston becomes leaky and non-effective immediately the temper is destroyed.