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T. Kirke Rose, London, Eng. (communication to the Secretary*) :—The authors have shown that, under certain conditions, the rate of dissolution of gold by chlorine and bromine is reduced by the addition of 10 per cent. of silver to the gold, and that the action is almost stopped when the silver amounts to 30 or 40 per cent. of the alloy. Even if full recognition is given to the practical way in which the work was done, however, it is to be regretted that Prof. Hofman and Mr. Magnusou did not determine the temperature at which the experiments were carried out. From the details given, it may be inferred that the temperature was raised by chemical action by about 20' C. when 21 g. of sulphuric acid was added, and that the mixture was then slowly cooled down during the experiment. When bromine or very weak chlorine solutions were used, there could not have been any perceptible heating-action. As the action of both chlorine and bromine is aided by heat, it follows that the stronger solutions of chlorine were given an unfair advantage over the weaker solutions, and over bromine. If the temperature had been the same in each case, I do not think that the conclusions deduced by Prof. Hofman and Mr. Magnuson' would have been found to be justified. (This is speaking generally. In barrel-treatment the conditions are similar to those in the experiments.) The superior speed of bromine as compared with chlorine at equivalent strengths is not yet disproved, and the differences noted between strong and weak solutions of chlorine may have been largely a function of the temperature. Moreover, the authors used somewhat-coarse particles of gold, and did not try how far time was a factor, although it is obvi-

Jan 1, 1906

By ANTON GRAY

In considering the possibilities and costs of discovering minerals by exploration. mineral occurrences may be classified roughly according to the size of the target they offer to the various methods that have been used to search them out. This classification is advantageous because the methods of search which might be expected to give results in one case may be totally inapplicable in others. Mineral deposits for the most part have been found in groups, or districts, in which the individual deposits occur under the same general geological conditions and usually contain more or less the same metals. There are, also, what are apparently isolated de- posits, although if the truth were fully known many of these probably would not be isolated. These districts, such as the Belgian Congo copper fields, the California Mother Lode, and the Linares lead district of Spain, form the first division of my classification. The second division is formed of the individual deposits of these districts, for example, Kambove mine in the Congo, the Kennedy-Argonaut vein in California, and the Cruz vein at Linares. The third division consists of the separate ore bodies that make up the deposits

Jan 1, 1949

By Robert Bell

THE " Tar-Sands." is the name which has been given to the extensive horizontal deposit of fine Cretaceous sand, blackened by tarry petroleum, which forms the banks of the last or lowest 130 miles of the Athabasca river before it terminates in Athabasca lake. The Cretaceous strata, to which these sands belong, extend northwesterly from Dakota all the way to this lake and for 500 miles beyond it. The Athabasca river forms the uppermost section of the Athabasca-Mackenzie, one of the great rivers of the world. It rises on the Pacific side of the Rocky mountains, westward of Edmonton, and flows north of east to a point called Athabasca. Landing, 100 miles north of Edmonton, where it turns northward and runs about 280 miles before it falls into the west end of Athabasca lake. The section of this river-system which discharges the lake just named into Great Slave lake, is called Slave river, and below the latter lake it becomes the Mackenzie river. Along the section of 280 miles of the Athabasca river above mentioned, the Cretaceous strata consist of bluish-gray and drab-gray marls, on top, from Athabasca Landing to Drowned rapid, 110 miles down stream; then heavily bedded gray sandstones, 225 ft. in greatest thickness, underlying these, form the banks for about 40 miles further. The strata appear to be horizontal, but they really clip very slightly to the southward. At Drowned rapid, we see the first of the tar-sands resting on almost horizontal beds of bluish-gray limestone of Devonian age. In some places the limestone is associated with shaly or marly bands. Notwithstanding the great hiatus between the two series, the horizontal tar-sands lie conformably upon the almost level upper beds of the limestone wherever the two formations are seen together, all along the river, throughout a

Mar 1, 1908

By Ralph H. Sweetser

OF SPECIAL importance in the design and construction of an iron blast-furnace plant are tile raw materials to be employed. Obviously the iron must come from some ore of that metal, but the many kinds available lead to important differences in plant arrangement, and in the design of furnaces and accessory equipment. For instance, the bulk of the gangue in the ore is subject to wide variation as is that of the ash in the fuel. A gradual increase in the bulk of raw material necessary to produce a ton of pig iron has been noted, but this has been more than offset, so far as costs of operation are concerned, by improvements in the machinery used for handling large quantities of ore. coal limestone, and slag. The mechanization of coal and iron-ore mining. the building of big ore boats and limestone carriers, of ore docks for fast loading and unloading, and the general use of heavy railroad equipment have all contributed to greatly reducing the number of man- hours required to mine, transport, and manufacture the raw materials into a ton of pig iron. This looks like a big saving and it is. If it were not for these big labor saving machines it would be impossible to produce the tonnage of iron and steel that is made each year in this country. On the other hand, the total capital investment necessary to bring down the man-hours per ton of pig iron to a 2.3 hours average at the blast furnace and to a total of only 12 man-hours from ore to metal (see Table 1) is so great that even the present high price of pig iron is probably not far above the true cost of manufacture when all the fixed charges are properly included.

Jan 1, 1939

By DR. RICHARD RATHBUN

ON behalf of the Regents and the Secretary of the Smithsonian Institution, it gives me great pleasure to welcome you to the National Museum; but it is to your own museum, since it belongs to you in common with all the people of the country. Still young in a life which has been beset with many difficulties, it has gathered strength and attained a growth quite unprecedented. In fact, it is this very growth which has been the chief cause of trouble, always leading far and away beyond the capacity for storage ; and to-day there is nearly as much material contained in outside buildings as is displayed in this one. You will, accordingly, find the collections crowded, the cases so close together that their contents are often difficult to view, and the arrangement generally lacking symmetry. You may, therefore, be inclined to regard us as poor custodians of the collections of a great nation, but I beg you to withhold your judgment for a while. From the beginning there has been abundant zeal and activity and a proper direction of affairs, but space and money have been lacking. There is now a prospect of better times. All about you here is a beautiful park, but without. a covering it is not adapted to museum purposes. Upon it, however, a new large building is going up, so extensive in its dimensions that technology can soon be given a fitting home, thus realizing one of the earliest aspirations of the Regents. Some sixty-five years ago the extensive returns of specimens from the famous Wilkes Exploring Expedition around the world began to reach Washington, where they were deposited in the Patent Office Building, and formed practically the first of the National Collections. Six years later the Smithsonian Institution, based upon the bequest of James Smithson, was

Jul 1, 1905

By W. S. Ayres

BACK in the early nineties the old Dickerson iron mine in Morris county, N. J., was operated by a vertical shaft 850 ft. deep and by a continuing slope for more than 1000 ft. more 011 an incline of 65", together making the vertical depth about 1800 ft. I was then the general superintendent there. This mine, named for a former governor of New Jersey, had been worked more or less continuously from long before the American Revolution and up to this particular time. The pumping equipment was of the old-time Cornish type, with its long pump-rods running down the vertical shaft and the slope to the sump at its bottom. It was operated by a large flywheel engine in the engine room and all angles were turned by the usual bobs. Saturday was the day fixed for lowering the "suction" into the deepened sump at the bottom of the advancing slope. The mine foreman had gone down with the morning shift to superintend this very vital and particular work, which consisted not only of lowering the "suction" into the sump immediately after the pump had been stopped, but of securing it to the rock and putting in the added sections of column-pipe and of tightening up the numerous bolts at their joints, all before the water rose to the point of working. At an appointed time during the forenoon I had agreed to go down into the mine and join the mine foreman in consultation over any difficulties that might have arisen. At the time agreed I went down by the cage to the bottom of the vertical 850-ft. shaft, and then by ladders down the slope for over 1000 ft. more.

Jan 1, 1930

By G. G. Biggar

A MATERIAL contribution to the success of our Armies in the field has been the portable pipe-line system. These are the words of Brigadier General R. F. Fowler, chief of the supply division of the War Department. The portable pipe line is one of the "secret weapons" the American forces employed in their swift advances through Tunisia, Sicily, and Italy. Constructed of a light steel so flexible it can be snaked around trees, it can be laid at a rate of ten to thirty miles daily right up to the fighting fronts. It has played a major role in supplying combat troops with products varying from petroleum to water.

Jan 1, 1943

By G. W. Leney

Iron ores occur in such a wide variety of forms that nearly every kind of prospecting, geological knowledge, and geophysical technique has some application in the search for them. The type of orebody that is considered desirable depends on political and economic considerations, on transportation and markets, on the characteristics of the orebody, on the metallurgy of the ore, and on its comparison with other available ores. In North America, materials that can be efficiently processed into high grade concentrates and pellets are now the object of most exploration work. These are usually shallow, relatively unoxidized, metamorphosed iron formations that are particularly suitable for geophysical methods of exploration. Magnetic surveys are used for the direct discovery of new orebodies, for mapping stratigraphy and structure, and at times to locate oxidized zones in magnetic iron formation. Gravity mapping provides supplementary information, indicates gross tonnages, is useful in regional studies, and can discover non-magnetic orebodies. Electrical methods have not been fully exploited but self-potential, resistivity, applied potential, electromagnetic and perhaps induced polarization surveys all have restricted but highly useful applications. The use of all geophysical techniques promises to increase as the number of exposed easily discoverable orebodies decreases. A high consumption of steel, and consequently of iron ore is the chief characteristic of an industrial society and this consumption has been increasing at an average rate of about 35% every ten years for the past century. To supply this demand, iron ores and iron bearing materials in a wide variety of forms have been exploited on every inhabited continent and in nearly every country. Nearly every kind of prospecting, geological knowledge and geophysical technique has some application in the search for them. The type of orebody that is con-

Jan 1, 1964

By Gerhard Derge

The rapidity of oxygen steelmaking has created renewed interesl in the mechanisms and kinetics of the various processes involved. These studies can now be approached with increased confidence because of the more adequate thermodynamics, physical chernislry, and relevant engineering infornzation available. These combine to offer promise of useful control and automation if the details of each specific problem can be sufficiently well-defined. The hot filament microscope provides new insig-hi into many of these problems by direct observation at temperature, allowing the appraisal of the relative importance of thermal gradients, convection, and intermediate phases. All of these have a direct bearing on the overall rates and control of most pyrometallurgical processes. It is one of the special privileges of the Howe Lecturer to become better acquainted with this distinguished man. All of us interested in the metallurgy of iron and steel have developed some sense of his widespread influence by the annual reference to his work in these Memorial Lectures. Each lecturer since 1923 has been able to identify his personal specialty with the broad interests of Professor Howe. This has become even more rewarding with the background information from Professor Gensamer's monograph, "Henry Marion Howe's Contributions to Metallurgy, which brings out his happy combination of intellectual and professional activities. Beyond this, I found my personal bond with Professor Howe in his book on The Metallurgy of Sleel first published in 1891.' After a detailed discussion of the dephosphorizing action of slags, he relates the mineral species identified in the frozen sample to the chemistry of the fused slag with the question, "Is it not most philosophic to hold that these independent entities were wholly integrated in the initial magma; that their presence in it was wholly

Jan 1, 1968

By Edwards Wichers

The purpose of this paper is to set forth the matters of principal interest in connection with work done in the past few years on the purification of the metals of the platinum group, including the study and modification of methods already in the literature and the development of new procedures. For the most part, the results will be given in summary form, reserving the publication of detailed data and directions for a forthcorning paper to be issued by the Bureau of Standards. In recent years increasing interest has been shown in the preparation of the pure platinum metals, both by those concerned with the manufacture of the metals and their alloys for scientific and industrial purposes and those who are engaged in the study of the chemical or physical properties of the elements. The purification of the metals usually has been regarded as a matter so involved and difficult as to require the attention of specialists. It is hoped that this paper will show that any of the metals can be prepared in any desired degree of purity by relatively simple straightforward chemical methods. For the most part, it is thought that the methods given are suitable for small-scale refineries as well as for the laboratory; also, that they will bring the time required for the purification of any of the metals within reasonable limits. The new procedure suggested for purifying platinum should prove to be much shorter than any methods described in the literature. Treatment of Platinum Ore As is well known, the principal source of the platinum metals is a mixture of several native alloys of the metals, found chiefly in naturally concentrated deposits in stream beds or alluvial material. Without attempting to enumerate all of the minerals present, it may be said that the concentrated ore from such sources contains all of the six platinum

Jan 1, 1928

By Robert H. Richards

The extent to which sizing by sieves should be carried, as a preliminary to the separation, by jigging, of minerals of different specific gravities, has been a matter of controversy for many years. The subject has been investigated by several authorities, yet the ground does not seem to have been completely covered, nor are the questions involved entirely settled. For my present purpose I shall refer to but three investigators—Rittinger, Munroe, and Hoppe. In seeking additional light, I have gone over part of the old ground which has been considered satisfactorily settled; and since these preliminary tests have thrown light on some points, they have been included in this paper. In the investigations here described, I have confined myself, for several reasons, wholly to small sizes—grains of 0.1 inch in diameter and less. Rittinger's work was mainly done upon larger sizes, and there is much need among millmen of information concerning the smaller sizes. Moreover, these sizes brought the investigation within the means at my disposal. The laws that have been claimed as the laws of jigging by the several authorities are: 1. The law of equal-settling particles. 2. The lam of interstitial currents. 3. The law of acceleration. 4. The law of suction. The first of these has been considered by investigators, generally, to be the most important of all, and the larger part of the work of jigging is thought to be governed by it. But that it does not cover the whole of jigging is clear to all; and to account for the increased efficiency which we may call the extra jigging-catch, the other three laws have been advanced. The investigation described in this paper was undertaken to determine, as far as possible, to what extent each of the four laws con-

Jan 1, 1895

By C. D. Woodward

THE Anaconda Copper Mining Co. purchases 25,000 kw. of electric power for its mining operations at Butte Mont. This power is delivered, over duplicate feeders, in the form of 60-cycle, 2400-volt, three-phase current, to five compressor plants, where most of the energy is used for driving air compressors. At the compressor plants are located the switching apparatus for controlling the 2400-volt power and distributing it to the various mines. At these points, also, there are a number of motor-generator sets for converting the alternating current to 275-volt. direct current for the haulage systems. Pole lines convey the power from the compressor plants to outdoor transformer substations at most of the mines. When it is not economical to distribute the power at the lower voltages in the mines, transformers and motor-generator sets are placed at strategic points .underground. All power is purchased on a maximum-demand basis, therefore there is installed at one of the compressor plants an eight-element totalizing graphic wattmeter. This instrument records simultaneously the value of all power taken at the numerous points of delivery, which not only eliminates the diversity factor but permits load dispatching between compressor and pumping plants, and thus materially reduces the maximum demand from the power system. As most of the mine hoisting is done, by 90-lb. compressed-air winding engines, the air-compressor equipment for the winding engines and mining operations is quite extensive. The standard air compressor has a rating of 7500 cu. ft. per min. of free air, and most of the compressors are directly connected to synchronous motors. The synchronous motors are designed for 80 per cent. leading power factor, thus facilitating power-factor correction of total mine load. Consequently by cooperation with the power company, the voltage of the power received at the compressor plants is constant.

Jan 2, 1922

Gentlemen of the American Institute of Mining Engineers.—As you well know an application is about to be made to Congress, by the American Society of Civil Engineers, for the appointment of a cornmission composed of persons skilled in the production and use of iron, steel, and other structural materials, whose duty it shall be to test the strength, elasticity, and other quatities of such materials ; not simply the substances used as such, but the members of large structures composed of such materials, of the forms and sizes in which they are actually used. As I understand, the papers that will be read here to-night will have for their object to show the necessity for such tests, and therefore the necessity for the commission asked for. As the representative of the Society of Civil Engineers, I have to thank you, gentlemen of the Mining Engineers, for the great zeal with which yon have taken up this subject, and seconded the efforts of the Civil Engineers; or, perhaps I ought rather to say, initiated the efforts to get a suitable commission appointed to obtain most vitally important information which it is admitted on all hands we do not now possess. In drawing up the memorial to Congress, in connection with some of the ablest and best informed of our Society, and in all the discossions on the subject, I have been struck with the emphasis with which the confession is made, that so little is known of the strength of the larger-sized members constantly used in building structures of the magnitude which the present requirements of the country now demand. I presume the remarks made to-night will bring this out very prominently. This is no disgrace, for with the means here-

Jan 1, 1882

By Edmund Davenport

THE specific aim of this work has been to study certain forms of internal deterioration which occur in tungsten filaments when subjected to high temperatures under various conditions, and to determine the cause of such deterioration. This would naturally lead to a consideration of methods of control or means of prevention of the phenomena. The deterioration was first noticed as a peculiar condition in the grain boundaries of certain tungsten filaments which had been burned? for long periods in lamps. In these cases it was noted that the grain boundaries contained a number of minute black dots which were at first thought to be non-metallic inclusions. It was demonstrated later that these dots or pits, as they were designated, could be readily produced by burning filaments in an atmosphere of flowing hydrogen. This method was convenient and adequate for the purpose, and was adopted for most of the work discussed in this paper. The evidence accumulated to date indicates that these pits are actually small voids between the grains. The purpose of this paper is to present- the information on this interesting subject gathered during a period of about 3 years. As applied to tungsten, the subject appears to be of considerable importance, experience having shown that this pitting ?is frequently associated with poor performance of filaments in lamps. The question has arisen as to whether these intergranular pits are peculiar to tungsten, or if they occur in all metals. If they are found iii all metals, the facts will be of considerable theoretical interest, as the material at the grain boundary plays an important part in most of the current theories of the properties of metals and alloys.

Jan 1, 1927

By David H. Browne

The trite maxim that man is a tool-using animal might nowa-days be amended by saying that man is a tool-choosing animal. The chipped flint, at first all-sufficient, gave way to hammered bronze, and that, in turn, to wrought-iron and steel. As our knowledge of metals increases, we learn to specialize; we temper and anneal; we alloy and intermix; and we fashion for ourselves a metal suitable to our necessities. The knowledge of the properties and uses of the various metals and their alloys has become the capital of every constructive engineer, and the currency of every intelligent brass-founder aid blacksmith. Prom year to year, the specifications of the designer become more rigid, and the steel-maker is forced to study more closely the qualities obtainable by changing the treatment, or altering the composition, of his metal. Of making alloys there is no end. We have heard much, during the last decade, of manganese-steel and chrome-steel, of aluminum and tungsten, of titanium- and silicon- and copper-steels, and of every conceivable union into which steel could be coerced or cajoled. Without denying to each of these alloys novel and valuable properties, it. must be admitted that, of all alloys, the one which shows the greatest range of adaptability, and has met the largest measure of popular approval, is nickel-steel. Introduced to public notice by Mr. Riley, in 1889, its field of usefulness has been rapidly enlarged, until, at the present day, the use of nickel-steel is as thoroughly recognized as that of carbon- or manganese-steel. Concerning the properties of nickel-steel numerous articles have appeared in the technical journals. For the man in a hurry, who wishes to look up the properties and limitations of nickel-steel, these articles might almost as well be in the lost

Jan 1, 1900

By Francis O. Blackwell

There are few industries in which power is more important to successful operation than mining, and none in which it is so difficult to ohtain power cheaply. Fuel is usually expeusive in mining districts, ana the ma chinery may be widely scattered and located in places difficult of access. The work is often so intermittent and variable as to prevent the economical use of steam. Mining operations are likely to exhibit accumulations of comparatively small and inefficient engines, numerous boilers and long lines of wasteful steam-pipes. Conlpressed air, as a means of transmitting power, is so handicapped by losses in the compressors and piping that it is limited to short distances and to the operation of apparatus requiring power, without regard to cost. To-day, electricity is rapidly replacing other methods of power-distribution, primarily because it is practically independent of distance. By selecting a potential proportional to the length of transmission, the cost of electric conductors and the e5ciency are the same for all distances within reasonable limits. For instance, a given amount of power can be delivered either 528 ft. away at 100 volts, or 50 miles at 50,000 volts, with the same total of copper per H.P. and with exactly the same loss of power in the transmissioo-circuk. This independence of distance permits the selection of the place most advantageous for power-development as a site for an electric power-plant, and the co~~centration there of the generation of all the power required within a radius of many miles. The powel.-site may be at a fall of water, if one is available, or a steam-plant can be built where fuel and supplies are cheapest, or where suflicient water is available for boiler-feed and condensing purposes.

Jan 1, 1904

By F. J. Williams

BARITE, naturally occurring barium sulphate, is the chief barium mineral that is produced commercially. Barite is also called "barytes," "heavy spar," sometimes "baryta" and, locally in Missouri, "tiff." Pure barite is white, opaque to transparent. It crystallizes in the orthorhombic system, frequently with twinning. Impurities cause a wide variation in color, commonly buff, gray and white with irregular reddish iron stains. Less frequently found are shades of yellow, green, blue, brown, and black. The rock is brittle and breaks with an uneven fracture, although specimens from some of the residual deposits, particularly in Missouri, appear to have a cleavage due to the separation of the different layers of deposition. The hardness varies from 2.5 to 3.5 on Mohs' scale and different localities are said to produce either "hard" or "soft" barite. This generally refers to the ease of grinding of the product. The specific gravity of pure barite is 4.5 and this will vary downward, depending on the impurities present. The mineral has a white streak and a pearly to vitreous or sometimes stony luster. Pure barite contains 65.7 pct BaO and 34.3 pct SO3. Witherite, native barium carbonate, is not mined in the United States at the present time although a number of occurrences have been reported. A small quantity of witherite has been removed from a mine at El Portal, California, but the area high in witherite was small and soon depleted. The bulk of the deposit is predominantly barite. Great Britain is the world source of witherite and small quantities are imported into the United States. DISTRIBUTION OF DEPOSITS Occurrence of barite is widespread; it has been reported on all the continents and in all the major countries of the world. Deposits vary from those containing millions of tons down to scattered rock fragments

Jan 1, 1949

By S. F. Shaw

IN 1913, the Tiro General mine, at Charcas, S.L.P., Mexico, which had been making from 125 to 150 gal. of water per min., was allowed to become flooded, after all the pumps had been removed, and in 1918 the problem of unwatering it came up for solution. There are two vertical shafts, the Tiro General, 1390 ft., and the San Fernando, 1225 ft. in depth, with five connecting levels between them. The San Fernando shaft had been partly retimbered, while the Tiro General had been newly timbered from the collar to, 1090 ft. in depth. It had been possible to place guides in only one compartment of the Tiro General, from the collar to the seventh or 850-ft. level, to which it was necessary to lower the water before station pumps could be installed. Soundings indicated that compartments in the Tiro General were open to 1082 and 428 ft., and in the San Fernando shaft to 471, 488, and 586 ft. The water had risen to a point 140 ft. below the collar of the Tiro General shaft. PUMPING EQUIPMENT The steam plant at the Tiro General shaft includes one 300-hp., one 150-hp. and one 100-hp. Erie City water-tube boiler, and two 160-hp. Heine water-tube boilers. All but one of these boilers were supposed to be in good shape, but it was soon discovered that six years of idleness in a climate that is foggy for several months of the year had left them in poor condition. The compressed-air plant comprises one Nordberg cross-compound compressor with piston displacement of approximately 2500 cu. ft. of free air compressed to 96 lb. per sq. in.; and another Nordberg cross-compound with piston displacement of 1235 cu. ft. of free air, to the same pressure.

Jan 2, 1920

By T. D. Yensen

I. INTRODUCTION IT is safe to say that of all the different materials that go to make up electrical machinery, iron is the most important. Upon its -magnetic and electrical quality depends not only the efficiency of the machine but, to a very large extent, the cost. Aside from the mechanical strength, there are three characteristics of iron that are of importance in this connection, viz., magnetic hysteresis, electrical resistance, and magnetic permeability. In the homopolar machine, where the magnetic flux is unidirectional, permeability is the only important factor, but in all other machines the flux is reversed in one or more parts and causes losses due to hysteresis and eddy currents. The eddy-current loss depends largely upon the electrical resistance of the iron; the higher the resistance the lower the loss, under otherwise identical conditions. These hysteresis and eddy-current losses cause heating of the machine, and as they depend upon the magnetic density in the iron, this density must be regulated so that the heating shall not be excessive. If the hysteresis and eddy-current Josses and the permeability of the magnetic circuit will permit an increase in the magnetic density, or, in other words, a decrease in the amount of iron, this in turn will mean a decrease in the amount of copper needed, with a consequent decrease in the copper loss. It is thus seen that; indirectly as well as directly, the above characteristics have an important bearing on both the efficiency and the cost of electrical machinery. In general, it may be said that iron for electrical machinery should have the following characteristics: (1) low hysteresis loss, (2) high electrical resistance, and (3) high permeability. These are the characteristics that investigators have been striving to attain since electrical machinery first came into use.

Jan 2, 1916

By G. Chesneau

Two great discoveries of this century have diminished the dangers of fiery coal-mines,—the sifety-lamp, conceived in 1815 by Sir Humphrey Davy and successively improved by many engineers, such as Clanny, Marsaut, Mueseler, Fumat, etc., and safety-explosives, the appearance of which is comparatively recent, hut which, thanks to the persevering labors of several technical commissions (especially the French commission on explosives), and of the manufacturers and experimental users of these powders, appear likely to play, in the protection of the miner, a part as important as that of the safetylamp itself. Brit while it is true that by the use of a safety-lamp of approved form, and the exclusive employment, with all prescribed precautions, of these new explosives, complete security should be assured, even in highly fiery atmospheres, experience has shown that the imprudence of workmen, or the bad condition of a lamp, may nullify these protective means, so that it ought to be the constant care of the engineers of fiery mines to dilute the fire-damp by good ventilation so far as to maintain always and in all parts of a mine a proportion of this gas below the lower limit of explosiveness belonging to a mixture of air and methane. Good ventilation still remains the best preventive of explosions from fire-damp, and since, even with a rational and well-controlled mine-ventilation, the volumes of air traversing galleries and rooms are liable to vary within wide limits by reason of open doors, falls of rock, or other accidental causes, it follows that but a few thousandths of fire-damp should be left in the normal atmosphere of the mine-workings, so that a considerable

Jan 1, 1894