82.07; hydrogen, 5.30; oxygen, 3.35; nitrogen, 2 72; sulphur, 1.64; ash, 4·90; loss, 0·02. The samples taken from the level drives, showing a specific gravity of 1.231, are scarcely less satisfactory. On first firing up, the coal is said to give out smoke rather freely, but this soon passes off, and its deposits of soot are not more than would accrue from good English coal. The following remarks of Mr. Madden, chief engineer of Her Majesty's ship 'Ocean,' are very conclusive as to its merits :-" Keeping steam with ease at 50 lbs. pressure. Full speed for five hours with a continuous steam exhaust blast from four cylinders, being a very severe test of evaporative qualities for bituminous coal, which involves large quantities of smoke each firing for a short time, but if used in ordinary boilers, without blast and slow combustion this would be considerably reduced. I consider the two samples as tested above to be equal in general steaming properties to English North Country; and compared with Welsh, repeatedly tested under same circumstances, as shown to be best Welsh 5 cwt. = 7 cwt. Takasima."

We have recently visited the Hayle Foundry Wharf at Nine Elms to see the operation of some pneumatic stamps. The importance of introducing the utmost economy into the ore-dressing arrangements of the tin mines of Cornwall renders this invention of the highest importance. The following is a brief description of the machine:

In the pneumatic stamp the motion is conveyed from the crank cap and guide cross-head, on piston-rod, by an ordinary connecting-rod. Attached to its lower end is the piston-rod, and piston packed with double reverse cup-leather packings; the piston is 44 inches diameter, and operates freely in the upper part of a gunmetal cylinder 3 feet in length; attached to the bottom of this cylinder, by a socket in the usual manner, is the round stamp-head of chilled cast-iron, 9 inches diameter. The upper end of the cylinder is bored, to receive the piston, to a depth of 14 inches; the piston-rod plays air-tight through the cylinder cover, which is screwed metal to metal on the cylinder. The working barrel of cylinder is pierced with two sets of small holes, for the ingress and egress of air, discharging the air behind the piston after it has been once used as an elastic cushion. Suppose the head to be set in motion with the crank in a horizontal position, the piston being in the middle, vertically, of the working barrel of cylinder, and midway between the two sets of air-holes referred to. As the crank and attached piston rise, the air is compressed between the piston and cylinder cover, and the cylinder, with stamp-head attached, is forced upwards. When in rapid motion, the elasticity of the compressed air between the piston and cover flings the cylinder, with head, some inches above the range due to the motion of the crank; on the descent of the piston below the bottom set of holes in the

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cylinder, the air is compressed in a similar manner, and the cylinder is forced down by the compressed air between the piston and cylinder bottom, until the stamp-head strikes the ore in a coffer-trough; thus, whether the quantity of ore be large or small, the blow is always effective, the only difference in the working of the machine being a shorter or longer vertical play of the cylinder and head.

The committee appointed by the North of England Institute of Mining Engineers to investigate the action of safety cages and hooks have made their report. After a most careful investigation of all the inventions which were brought before them, and they were very numerous, they have arrived at the following conclusion:"That there are really but two different classes, namely, those which come into operation every time the chain is slackened, and those which do so only when the cage is actually falling or descending at a speed almost equal to that of a falling body. Inventions of the first class are very numerous; the second class has one sole exponent, Calow, and both depend on the action of springs (which are always subject to derangement) to initiate the grip, which intensifies itself by being drawn more and more into gear by friction on the guides. Both systems have their advantages and disadvantages; for even Calow's, although it does not wear so much as the others by being constantly in motion at the top and bottom of the pit, yet is apt to stick in the shaft if by any cause the cage receives a sudden jerk."

In conclusion the committee say:-"It must be admitted that, with every desire to see some efficient apparatus in use at every colliery to prevent the lamentable loss of life that occasionally occurs, your committee have felt an instinctive distrust of the various modes hitherto proposed for doing so, which distrust has not been altogether overcome by the investigation that has been gone into. Up to the present time there seems some element wanting to perfect these machines (some of which are excessively ingenious) and render them really reliable, and it is much to be desired that such an improvement may be arrived at speedily. With this feeling your committee cannot express an opinion as to the necessity for the adoption of any of these provisions for safety, and can only lay before you the facts they have acquired, with such deductions from statistics and observations as have presented themselves, and which it is hoped will materially assist in considering the merits of new inventions."

Papers on the Theory and Practice of Coal Mining. By George Fowler, M.E. W. M. Hutchings. London. Mr. Fowler has read before the Institution of Civil Engineers, and other societies, papers "On the Relative Safety of different Modes of Working Coal," and on kindred subjects. These papers are now gathered together, and, reconstructed, are presented to the public in a very useful form. Each mode of working coal is carefully

described, and the author's views are given as to the relative values of the several systems. It is not practicable, did we even deem it advisable, to enter into any discussion on these questions. We must refer all of our readers who are interested in the subject of mine ventilation to the book itself, which they will find very full of useful information.

METALLURGY.

It is our duty to record such of the numerous attempts as are made from time to time to improve the make of iron and steel as may appear to possess merit. It is not a new idea to use the alkaline metals for removing deleterious ingredients from iron; but we are not aware that it has hitherto been proposed, as is now done by Girard and Poulain, to force the vapour of potassium or sodium through the molten metal. They propose to saturate the fuel with carbonate of soda, and dry it, or to mix common salt with the fluxing materials. These inventors, however, appear to place most confidence in a process for blowing those vapours mixed with moist air, or moist carbonic oxide, through the melted metal in a Bessemer converter. Pure iron or steel is said to be thus obtainable at pleasure. If experience proves this, we shall soon hear more of this process.

The continually-increasing demand for high-class pig-iron and iron ores, caused by the extension of the Bessemer process, has brought into notice the red hematite and magnetic ores of Norway as a possible source of supply for the Continent. According to a statement published in the 'Berggeist,' a paper representing the metallurgical interests of Westphalia and the Rhine provinces, it has recently been suggested to employ the magnetic ores raised in the neighbourhood of Arendal for the production of Bessemer iron on the spot, the total output of which the mines are capable being estimated at 50,000 tons of 40 per cent. annually, which it is proposed to smelt in two moderate-sized furnaces with coke made on the spot from washed English small coal. Whether such a proposal is likely to be commercially successful may be doubted; but the point is in so far of interest as showing how completely iron making is now governed by the item of cheap fuel; the making of charcoal pig-iron even in a thickly-wooded country like Norway being nearly at an end, for out of fifteen blast-furnaces in the southern part of the country only five are now in blast, the cost of production of pig-iron being nearly 67. per ton, owing to the high price of charcoal. On the system proposed, the cost of No. 1 grey Bessemer iron is computed at 688. 6d. per ton, which, could it be realized, would leave a fair margin on the selling price of hematite pig-iron in our north-eastern ports.

The question of the exact nature of the changes involved in the conversion of pig-iron into steel in the Bessemer process, or rather of the composition of the pig-metal employed, is still a matter of great uncertainty. That sulphur, phosphorus, and copper are in no degree removed during the process, and that consequently these impurities must be absent from the metal treated, is proved by all the analytical investigations made in this country as well as in Sweden and Austria. As regards the question of silicon, Professor Jordan, of Paris, has recently pointed out, in a memoir published in the Revue Universelle,' the probability that the enormous heat developed in the process is mainly due to the combustion of this element, because the whole of the heat produced by the burning of silicon to silica, of silicate of protoxide of iron in the slag, and the subsequent formation is entirely retained in the metallic bath, while that produced in the combustion of the carbon to carbonic oxide is in great part carried out in the current of flame and heated gases issuing from the mouth of the converter. The exactitude of this view cannot of course be positively demonstrated, because neither the calorific power of silicon nor its specific heat has yet been determined. If, however, we assume with Professor Jordan, which is not improbable, that these factors are the same for silicon as for carbon, it can be shown that in the conversion of a pig-iron containing 4 25 per cent. of carbon and 2 per cent. of silicon that the amount of heat developed by the combustion of the latter element is more than six times as much as that obtained from the former. In proof of this statement it is asserted that the Bessemer process could only be successfully carried out at Terrenoire in France when the metal was run direct from the blast-furnace to the converters, the small proportion of silicon, about 13 per cent., present being not sufficient to allow it to be cast into pigs and remelted, as is usually done. The dark grey No. 1 Bessemer pig-iron produced in Cumberland and Lancashire contains generally from 2-6 to 2.7 per cent. of silicon. It appears to be probable, however, that when too much silicon is present, or rather when its proportion as compared with that of the carbon is too high, it may not be entirely removed in the blowing.

The separation of sulphur and phosphorus from iron has long been a problem of much interest, especially so since the introduction of the Bessemer process. At the Working Men's International Exhibition at the Agricultural Hall, London, is a display of specimens of iron obtained, by a process invented by Sir Antonio Brady, from some of that dockyard refuse irreverently described as "Seely's pigs," and which has been the subject of discussion both in Parliament and by the press. These pigs were of different qualities, but were all largely contaminated with phosphorus and sulphur, and were supposed to be of little or no value. The presence of phos

phorus renders iron brittle when it is hot; the presence of sulphur renders it brittle when it is cold. The pigs containing both were worth in the market about 27. 58. a ton. By Sir Antonio's process the sulphur and the phosphorus is said to be extracted at a cost of about 35s. a ton, and the residual iron is described as "superb." One of the pieces exhibited is stated to have been beaten cold to the thinness of writing paper at one end, drawn to a point at the other, and then twisted by hand eight turns in an inch at a single heating. Massive bars are said to have been beaten cold until the surfaces on each side of the bend came into perfect contact, and a plate six inches wide and half an inch thick to have been beaten till its edges were in contact, the flat surface remaining horizontal. In neither case was there any trace of a flaw, either at the convexity of the curve, where the metal was stretched, or at the concavity, where it was compressed. Holes in a thick plate are labelled as having been enlarged by driving cones into them, and, in a word, the iron is described as having been knocked about in every possible way. At a very low estimate it is affirmed to be worth 147. a ton, and as there is plenty of the raw material to be had, the profit of the invention seems likely to be great.

A remarkable steel casting was made recently at the works of Messrs. Thomas Firth and Sons, Sheffield, which deserves a record. This casting is to form the shaft of the screw of the Dublin SteamPacket Company's vessel Munster,' and is about 15 feet in length by nearly 4 feet in diameter, and weighs over fifteen tons. This is one of the largest blocks of steel ever cast in this country.

The work of melting commenced about eight o'clock, in no fewer than five hundred and forty-four crucibles, each containing 64 lbs. the total quantity of steel being 34,816 lbs. At half-past twelve the work of casting began, and was rapidly completed, by the joint and perfectly organized action of 300 men. This metallurgical operation was a perfect triumph of mechanical skill.

The enormous difficulty and expense caused by the ever-accumulating mountains of slag produced by iron furnaces worked on the modern scale, often amounting to as much as 60 tons per furnace per day, has led to different proposals for utilizing these unpleasant ejecta, and we remember certain glowing descriptions of valuable results to be got by converting the despised slags into materials rivalling the finest porphyries and other ornamental rocks. The less ambitious but more practical plan of using them as paving stones has been for some time past under trial in Brussels, and, according to Kennis, with such success that they are to be employed generally in the repavement of that city. The process employed is simply that of allowing the cinder to run from the furnaces into an excavation sufficiently large to contain the whole daily yield of several furnaces, and the cooling is retarded by covering the surface