Search Documents

We have received from L. S. Cates, the following translation, by S. W. Mudd, of early mining methods in India: In Herodotus one finds a description how Darius by aid of his good horse and his good groom Oebares got himself the Kingdom of the Per-sians. He then set up in Persia twenty satrapies assigning to each a governor and fixing the tribute which was to be paid to him by the several nations. The following description of the method of getting the gold demanded of the Indians as tribute is copied directly from Book III Thalia, paragraphs 94 to 105 omitting the diversions of Herodotus which in one case consisted of a lapse of two pages following a semicolon before the author returned to the subject. The Indians, who are more numerous than any other nation with which we are acquainted paid a tribute exceeding that off every other people, to wit, three hundred and sixty talents of gold-dust. The way in which the Indians get the plentiful supply of gold, which enables then to furnish year by year so vast an amount of gold-dust to the King, is the following: Eastward of India lies a tract which is entirely sand. Here, in this desert, there live amid the sand great ants, in size somewhat less than clogs, but bigger than foxes. The Persian king has a number of them, which have been caught by the hunters in the land whereof we are speaking. These ants make their dwellings under ground, and like the Greek ants, which they very much resemble in shape, throw up sand-heaps as they burrow. Now the sand which they throw up is full of gold. The Indians, when they go into the desert to collect this sand, take three camels and harness them together, a female in the middle and a male on either side, in a leading-rein. The rider sits on the female, and they are particular to choose for the purpose one that has just dropped . her young; for their female camels can run as fast as horses, while they bear burdens very much better.

Jan 12, 1919

ZAY JEFFRIES, Cleveland, Ohio (written discussion?).-The authors conclude that there is a certain average size of precipitated CuAl2 par-ticle which produces maximum strength and hardness in duralumin; that when the size of particle is smaller or larger than this particular size the hardness decreases. The writer agrees with this conclusion, because it seems to he directly indicated by the facts. Why does duralumin present this apparent discrepancy? Let us con-sider some physical aspects of the precipitation of CuAl2 from a saturated solution on cooling. When a molecule of CuAI3 is removed from the solvent, or matrix, and added to another group of CuAl2 molecules, as is known to occur on slow cooling, the forces of adhesion between the CuAl2 molecule and the solvent have been exceeded. Since a. change in tem-perature only is sufficient to cause precipitation, it must also be sufficient to cause the loss of adhesion bonds between the excess CuAl2 molecules and the solvent, or matrix. Lost adhesion bonds means loss of cohesion of the mass as a whole. When duralumin is cooled from 500° in a furnace, globules of CuAl2, large enough to be seen easily with a high-power microscope, are formed. There are, however, globules so small as to be hardly distinguishable, and others too small to be resolved are suggested by the non-uniformity of the surface appearance of the section. As the smallest globule of CuAl2 resolvable with a high-power microscope contains about 2,000,-000,000 molecules, it is evident that with rapid cooling submicroscopic particles of CuAl2 must be present in large numbers; in fact, after quench-

Jan 12, 1919

THE CHAIRMAN ( F. K. COPELAND, * Chicago, ,Ill.).-This is an interest-ing and very troublesome proposition to all of us. Ten or fifteen years ago, when the old-fashioned idea prevailed that a man was responsible for his own health and safety, that if anything happened to him it was his own lookout; we got along without this problem; but with the advent of accident compensation, with the agitation that there is all the time for pensions, sick benefits, and the responsibility of a company for the health of its employees, whenever you take a man on, that phase is becoming more and more important. One cannot afford to hire a man who is blind in one eye, even though he may have perfect sight in the other eye; if he loses that one eye, if lie becomes a total disability, the company is liable for the man's complete sight. Another thing that should make us particularly interested in this problem is the fact that the unions are very much opposed to it. One of the requirements of this steel unpleasantness is that the companies abandon their physical examination of employees. It is a very difficult problem to examine 400 or 500 men as intelligently as possible and decide whether a man on this or that side of the line is accepted. T. T. READ, Washington, D. C.-The United States. Bureau of Mines has in progress at the present time a study of the effect of underground atmospheric conditions on the safety and health of the workers. Im-proved methods have been employed and it is an excellent and ex-tremely valuable piece of research work.

Jan 12, 1919

CARL A. WENDELL, New York, N. Y. (written discussion*) .-I have never seen in print anything that even remotely has approached this article in clearness and important conclusions in conjunction with work done on the sink-and-float test. I have had many hundreds of these tests made and on different specific gravity solutions and the resultant product analyzed, but I have never grasped nor been able to show what this article sets forth. This article brings out one factor very clearly to my mind; what is to take the place of the solutions of different specific gravities used to obtain the laboratory results, when it comes to washing on a large scale, since water has one constant weight only? The answer is, sizing of coal. And as we know the importance of size versus specific gravity of the material to be washed, perhaps defined (practical) lines can ultimately be gotten up so that the sizing, if any, may be determined at the same time as the laboratory work on the coal is being done. G. R. DELAMATER, ? Steelton, Pa. (written discussion?).-The authors' deductions are well founded and although they disclaim any wide experience in commercial coal washing, practically all of the data presented are applicable to coals of all parts of this country. The paper clearly sets forth the great necessity of careful preliminary investiga-tion of each contemplated washery undertaking and contains the follow-ing very true statements. "It is not safe to assume that any coal which can he successfully washed on coarse coal jigs can be cleaned more com-pletely by washing at a finer size on tables," and "The effect of finer crushing upon the completeness with which impurities may be separated from coal depends upon two opposing tendencies. First, that the more finely a raw coal is crushed, the more completely will the particles of impurities be detached from the particles of clean coal. Second, the finer a coal is crushed the more difficult it becomes to separate the pieces of clean refuse from the pieces of clean coal."

Jan 12, 1919

In a letter to Prof. L. P. Breckenridge, chairman, urging the continua-tion of the Fuel Conservation Committee of the Engineering Council, Edwin Ludlow calls attention to the millions of tons of culm in the an-thracite region that can be utilized in properly equipped plants and the electricity generated transmitted to. New York, Philadelphia, and other nearby cities. He says: "Experiments have shown the economic value of No. 4 Buckwheat, which passes through a 1/16-in. mesh and over a 1/32-in. mesh. Culm passing through a 1/32-in- mesh is pulverized until it passes through a 300 mesh and is then burned under boilers. Two plants of this kind are now in successful operation in the anthracite region. Another rather interesting experiment was using 30 per cent. of this pulverized coal with 70 per cent. of oil in the generation of steam in the place of pure oil. This utilization of the fine anthracite, which has always been a waste product and thrown away, is not only fuel conservation in its truest sense but in the case of a bituminous strike, when no strike is contemplated in the anthracite field, will furnish fuel to manufacturing plants that otherwise would be obliged to shut down."

Jan 12, 1919

T. R. HARRISON, Washington, D. C. (written discussion *).-Ad-vantage will be taken of this occasion to mention briefly a form of double potentiometer which has been used at the Bureau of Standards for about 2 1/2 yr. in calibrating thermocouples. The calibrations referred to are those made by comparison to standard couples. In order to insure equality of temperature between the couples, the junctions are fused together; consideration of fundamental principles will show that this introduces no error. Two separate potentiometers are used, one connected to each thermocouple, and each potentiometer is provided with a reflecting galvanometer. The two spots of light are reflected on to a single scale, the galvanometers being set in such a position that the spots coincide on the scale at a point marked zero when the circuits are open or when the potentiometers are balanced. By setting one potentiometer to a desired value and adjusting the other so that both spots pass across the scale together as the temperature rises or falls, simultaneous readings are obtained. By making observations first with a rising temperature and then with a falling temperature, the rates of rise and fall being approximately equal, and taking the means of the results found, several minor errors such as those clue to differences in the time lags of the two systems, etc., are eliminated or greatly reduced. The differences between the values

Jan 12, 1919

W. 0. HOTCHKISS, * Madison, Wis.-It was fortunate, in a way, that this subject of income taxation came up during the war when the government could appeal, on the basis of patriotism, to men of large, business experience to undertake the work of formulating this matter and practically donate their services. At any other time the government would have been unable to secure the necessary number of men of like ability. There is one thing that must not be forgotten. In all cases, except the very largest and most important, the application of this income tax law to a mine is going to be made by clerks whose salaries are fixed by a Congress that appropriated a half billion of dollars for a war purpose and provided that $4000 should be the highest salary paid in the adminis-tration of that great sum. The Congress of the United States unfor-tunately seems almost entirely unaware of the fact that men of ability and experience are worth money and must be paid adequately if proper public service is to be secured. While the formulation of the broad plans for administering the law have been in the hands of. men of unusual ability, we have the future to guard, and, if possible, the mining industry should see to it that the Internal Revenue Department is permitted by Congress to pay salaries that will enable it to secure men of the ability and experience necessary to insure proper consideration of the industry. Another fact to which I would call attention is the difference between the business and the economic, or economists', points of view as to what a mine is. The economists have properly, from their point of view, classed a mine as a wasting asset, but the average metal mine is not a wasting asset if it is a real mine. The economists are correct in a broad sense in that every ton of ore taken out diminishes the orebody by that amount. When it comes to the consideration of an individual mine from the business standpoint, the future of that mine rests on unfore-seeable events-the discovery of new orebodies or the development of old bodies beyond the point of probable expectations. Every going mine must develop new ore each year to replace that extracted, and, .during all but the last one or two years of its activity, actually does so. Instead of being a "wasting asset" such a mine, from the practical stand-point which must control valuation, is an "increasing asset." From

Jan 12, 1919

G. M. TAYLOR,* Colorado Springs, Colo.-The ore treated at the United Eastern is primarily a gold one and is cyanided-the counter-current decantation method being employed. One of our employees visited this plant a few months ago and, on his return, reported that the moisture in the tailing was carrying 20 c. per ton, which would appear to be somewhat high. As this type of plant has been advocated by one of the recognized cyaniding engineering firms in the country, and a number of these plants are in successful operation, it does not seem to me that the dissolved loss could be so high, and I would like to know if any one can give any definite information on this point? J. V. N. DORR, New York, N. Y.-I am very glad that Mr. Taylor has raised this question. When I first read Mr. North's paper and saw his statement, that they had an actual dissolved loss of 21.5 c. per ton, I was very much puzzled at this high loss which appeared avoidable by another decantation or the addition of a rotary filter. Reading it again, however, I noted that the actual dissolved loss of 21.5 c. given was evi-dently obtained by multiplying the assay of solution discharged from Z. thickener by the tonnage. On the basis of 283 tons milled per clay, this means $56.54 going to the clam. He states, however, that he returns from. the dam into the system, 70 tons daily assaying 40 c. per ton or $28 per day, so it would seem reasonable, unless I have overlooked something to regard the actual dissolved loss as $56.54 less $28 or $28.54, equaling 10.8 c. per ton. Even this loss, however, is much higher than good practice elsewhere, and can be accounted for largely by the tonnage being handled, which I believe is 30 per cent. above the capacity planned.

Jan 12, 1919

F. G. SMITH, Waterbury, Conn.-I would like to ask whether small amounts of iron give the maximum resistance at a low temperature, and if the large amounts of iron raise the temperature at which the maximum resistance occurs? That is, with a small amount of iron, will a maximum be at, say, 10°? F. E. BASH.-With the small amount of iron, the maximum is at a lower temperature, and with the increase of iron, the maximum increases; it seems to come to a maximum and then decrease; that is, increasing the iron up to a certain value increases the temperature at which there is a maximum of resistance, and any increase of iron beyond that value will start decreasing this temperature. With 2 per cent. of iron, the maximum is lower than for 1.5 per cent. which was the value that we found to be satisfactory. F. L. DRIVER,* Jr., Harrison, N. J.-I would like to ask what chance there is of the instrument companies getting together and deciding on standards for both manganin and constantan? We make both of these alloys in this country and we find that each one of the instrument com-panies who buy these materials require different standards of specific electrical resistance and thermal e.m.f. For instance, some of our cus-tomers require an electrical resistance in manganin or therlo of 240 ohms per circular mil foot and others require it with a specific electrical resist-ance of 270 ohms per circular mil foot. They buy these alloys in relatively small quantities so that it means much extra melting and supervision when making up small quantities for each consumer. If something could be. clone to eliminate this, it would be a benefit to the instrument com-panies, who could secure their material more cheaply, and to the manu-facturers, who would not have to spend so much time and effort in special manufacturing.

Jan 12, 1919

W. M. CURSE, Mansfield, Ohio.-Outside of the commercial valu-ation of the material, for what purpose does this alloy-90 per cent. of copper, 6 ½ per cent. tin, 2 per cent. zinc, and 1 ½ per cent. Lead-seem to be eminently fitted? C. P. KARR.-So far as our tests go, it would be eminently fitted for steam valves and pistons, and for the work for which 88-10-2 bronze is generally used, although for very large castings it would not be superior to 88-8-4 bronze. P. E. MCKINNEY, * Washington, D. C.-Some time hack, clue to a desire to avoid some of the objectionable features of 88-10-2 bronze, particu-larly on heavy castings, also to save tin where possible, we took up the question of a substitute for 88-10-2 bronze, where red bronze was ordinarily specified. After trying most of the mixtures, we found that when using as low a tin content as is given in this proposed composi-

Jan 12, 1919

J. S. UNGER, ? Pittsburgh, Pa. (written discussion ?).-Firebricks intended for, the same purpose, but supplied by different manufacturers, may be of entirely different clays, contain different proportions of flint, calcined and plastic clays; the particles may vary widely in size; the water used to make the brick will vary; the pressure in molding will vary, depend-ing on whether the brick is hand made or power pressed; and the degree of burning in the same kiln will differ. These variables affect the melting point and the strength of the brick when heated. An important property, of a firebrick is its ability to resist heat and, at the same time, weight or load without serious deformation. The soft-ening point and the melting point of a firebrick may be several hundred degrees apart, and two bricks may show considerable difference in their softening points, but the melting points may be approximately the same. Bricks are not usually employed at temperatures close to their melting points. If they must withstand very high temperatures, the firebrick is discarded and a brick of more refractory material is used. Under these conditions' it is doubtful whether the determination of the melting point of a brick has much practical value. If the determination of the melting point is necessary, the test should he made on a portion of the original brick and not on a specially prepared sample. A small triangular pyramid with a base about 1 1/2 in. and 3 in. high can be sawed from the corner of the brick with a thin-bladed car-borundum wheel, without injuring or destroying the size of particles, the bond, or degree of burning of the original brick. This specimen can then he compared with standard Seger cones or tested by any other method desired.

Jan 12, 1919

R. W. NEWCOMB, New York, N. Y. (written discussion *).-This paper is particularly interesting to me, because it gives data on a much mooted question, viz., the serviceability of Le Chatelier (platinum-platinum-rhodium) thermocouples under severe industrial conditions. It has always been supposed that platinum-platinum-rhodium thermo-couples, used at high temperatures under strong reducing conditions, would not give long service and were subject to rapid volatilization. The fact, however, that the carefully kept records indicate that a little more than 3 gm. out of more than 830 gm. was lost over this considerable period, shows what kind of service can -be obtained from platinum-platinum-rhodium thermocouples,, when properly installed, and well cared for. While the writer has no actual figures on the loss of weight, etc. of platinum-platinum-rhodium thermocouples under service, he was told, by the man in charge of pyrometers at a large industrial plant in which over 400 platinum-platinum-rhodium thermocouples were installed in furnaces doing various kinds of heat-treating work, that the average maintenance cost, for materials alone, including platinum-platinum-rhodium wires and protecting tubes, was 27 c. per furnace, per month:

Jan 12, 1919

THE CHAIRMAN (F. K. COPELAND,* Chicago, Ill.).-At this particular time conditions existing in this, country, and elsewhere, make all questions of milling or smelting or mining, or anything else, absolutely secondary to the one question of labor. We have always devoted our attention largely to the efficiency of machinery, and to reductions in costs, etc., and have let this tremendous problem of our relation to labor more or less take its own chances. There has never been a time when those who are responsible for the operation of business of different kinds were as com-pletely at a loss as they are now, so that anything that can be brought out that relates to labor is, to my mind, of utmost importance. T. T. READ, Washington, D. C.-This formulation of a method of curtailing forces at the Copper Queen is a notable step in advance of our treatment of personnel in the mining industry. So far as I know, it is the

Jan 12, 1919

JAMES ASHWORTH, Livingstone, Alberta, Can. (written discussion*).-About the year 1878, the writer commenced to experiment on safety lamps, the results of which will be found in the Transactions of the North of England Institute of Mining and Mechanical Engineers 1879-1880, the Transactions of the Manchester Geological and Mining Society, and in the technical press. He has also made a careful investigation of the flame caps produced by chemically prepared methane when mixed with air in accurately measured percentages. Before the conclusion of these experiments he personally fitted the hydrogen gas test to a special pat-tern of the Ashworth-Gray patent safety lamp. Later, as pure hydrogen gas was not always available, the writer constructed a safety lamp that would separately burn oil and alcohol; and still later, a somewhat similar lamp to burn alcohol only for specially testing low percentages of methane. This lamp was known As the Ash-worth alcohol safety lamp.

Jan 12, 1919

By Franz Fohr

On July 27, 1919, there passed away a simple, unassuming gentle-man, who, throughout his life, allowed his intense modesty to keep him-self in the background and during his later years effaced himself so thoroughly that but few of his acquaintances knew aught of him. Yet he was one of our accomplished metallurgists, who did good work in the practice of his profession and lived an upright life. Now that he is no longer with us Franz Fohr cannot plead to be overlooked, and those who fondly remember him will be gratified by his receiving his due. Franz Fohr was born, Sept. 7, 1838, in Mannheim, Germany. Of his ancestry, education, and early career we know scarcely anything. We do not even know just when he came to America, or. what led him hither. The first record of his professional work in this country, found among his papers, shows that from July, 1870, to Jan. 1, 1872, he was superin-tendent of the Newark Smelting & Refining Works, then owned by Ed-ward Balbach & Son. At that time the Balbach works at Newark, established in 1850, and the Selby works at San Francisco, established about 1866, were the only important silver-lead refineries in the United States. Mr. Fohr may have been associated with the Balbachs for some time before he became superintendent of their plant or he may have come from Germany but a short time previously. At all events, it is certain that he was at that time an experienced and accomplished metallurgist. After leaving Newark and going to San Francisco, he soon formed a connection with Thomas H. Selby & Co. Early in 1874-this firm sent him to New York to procure information respecting the manufacture of white lead. His engagement in New York terminated on-Jan. 31, 1875. During 1875, Mr Fohr spent some time at Silver Islet and in the Lake Superior copper region, but of his work there no record remains. In the latter part of 1875, or early in 1876, he associated himself as metallur-gist with the Boston Silver Co., operating at Saint John's, Summit County, in which William L. Candler, of Boston, was the moving spirit. That company was developing its mine in 1875. At the end of that year it "had about 800 tons of ore on hand, about three-fourths of which is dress-ing ore, to be concentrated in its very systematic establishment and to be smelted into pig lead." Evidently Mr. Fohr was engaged for the latter purpose. Henry A. Vezin, erudite and painstaking, was the mechanical engineer for the company. In the fall of 1876, Anton Eilers took his family for the first time so far West as Denver and Mr. Fohr went with them. I do not think that Mr. Eilers had any connection with the Boston Silver Co., save possibly in a consulting capacity, but he visited Saint John's and the enduring friendship among Eilers, Fohr, and Vezin, which terminated only with their deaths, dated from that time.

Jan 12, 1919

Many of those who attended the meeting at Chicago spent the first part of the following week in Pittsburgh, when the Experiment Station of the Bureau of Mines was dedicated and the fourth annual First Aid and Mine Rescue Contests were, held. The Bureau buildings were open for inspection during the three days, Monday, Tuesday, and Wednesday. The dedicatory ceremonies were held in the Bureau of Mines main building, Monday morning, Sept. 29, Mr. T. J. Gillespie, representing the Pittsburgh Chamber of Commerce, presiding. In his address of welcome, Hon. E. V. Babcock, Mayor of Pittsburgh, said: "The reclamation work already done stands out conspicuously beneficial to industry and populace alike all over the United States. It has demonstrated methods of preservation of life and reclaiming of injured persons which are new and greatly beneficial to modern civiliza-tion. The establishment of this institution in Pittsburgh was greatly desired, and now it is here it is greatly appreciated." The response was given by First-Assistant Secretary of the Interior Vogelsang, who represented Secretary Franklin K. Lane. He said that the Bureau of Mines did more during the war for the triumph of American arms than any other institution.

Jan 11, 1919

F. WEIMER,* Washington, D. C. (written discussiont).-For electrical measuring instruments, especially those types that involve the Wheat-stone bridge or potentiometer principle and standards of electrical resist-ance, there has been, for a considerable time, a need for better resistance materials. For a satisfactory resistance material, much depends on the purposes for which it is to be used. For potentiometers and Wheatstone bridges, such as are in more or less general use, and the more common forms of resistance standards, a good quality of manganin answers fairly well. However, it should not be presumed that manganin is considered ideal for the purpose, for in measuring instruments and resistance stand-ards, there is still much to be desired. An experience of more than 10 years in the study of the resistance standards and resistance apparatus shows that manganin resistances change with time in a way that is very annoying and the maintenance of the unit of resistance to the desired accuracy requires an excessive amount of work or may be said to be prac-tically impossible. The changes in resistance are generally most rapid and erratic in resistances of very low and very high values. In resist-ances of low value, the resistance material is often in the form of thin sheets so that the surface is large and usually more or less unprotected from the atmosphere, or the oil in. the case of oil-immersed standards. In resistances of high value, the resistance material is in the form of fine wire and, therefore, the surface is large compared with the cross-section. In resistances of medium value, the surface is less, compared with the cross-section, or better protected, usually by a silk wrapping impregnated with shellac. This suggests that one of the difficulties with manganin is slow surface action or oxidation, even when an effort has been made to protect the surface from such action However, the changes observed cannot all be accounted for on this basis. There are, presumably, also some internal changes in the resistance material even when it has been annealed. Further; the changes in manganin resistances seem to be more or less independent of its electrical properties. In other respects, too, manganin is not ideal.

Jan 11, 1919

EUGENE MCAULIFFE, St. Louis, Mo. (written discussion*).-When we undertook the development of the Kathleen mine, near DuQuoin, certain features greatly influenced the construction and underground development. The country is very flat, so that the usual gravity yard movement of empty and loaded coal cars would entail a very heavy fill at the empty-car end of the tracks, with some form of car-pulling arrange-ment to move the loads where it was practically impossible to provide. a gravity movement. So the yard was made level, except for 1000 ft. (304 m.) under the two tipples, where the cars are moved by gravity and controlled under the main-shaft tipple by four Fairmont car retarders. Both tipples are spread sufficiently to admit of introducing a narrow-gage track and locomotive. One 18-ton locomotive is at present employed in moving empties clown to a point above the main-shaft tipple and the loads off the track scales clown into the storage yard; ultimately a 25-ton loco-motive will be employed on the loaded side of the tipple. This form of car movement and control will admit of handling empty and loaded cars

Jan 11, 1919

This brief resume of the events transpiring in Mexico, culled from the daily New York newspapers since the last Bulletin went to press, does not show any degree of improvement in the situation. MEXICO SEEKS TO AVOID BLAME FOR BANDIT RAIDS All foreign passengers leaving Nogales for Mexico on the Southern Pacific or Mexico Railroad. whose business would take them through territory occupied by the Yaqui Indians or Mexican bandits were requested by Mexican Consul Emilio Tamez to sign a statement that they relieve the Mexican government of responsi-bility for anything which might happen to them while in that part of Mexico. The Mexican consul stated, says the N. Y. Tribune, that this was by order of Mexican Ambassador Ignacio Bon ill as, at Washington. When the State Department was advised of this activity Secretary Phillips, in a message to the consulate at Tampico, according to the N. Y. Tribune, asserted that "compliance with the waiver requirement will not interfere with the relation existing between the United States and its citizens and that Americans so complying will in no way lose the protection of this government."

Jan 11, 1919

H. G. DAVIS, * Wilkes-Barre, Pa. (written discussion ? ).-The only practical method of testing mine air for gas, until recent years, was by the effect of the gas on the flame of the ordinary Davey Lamp, and it is quite surprising how nearly the correct percentage of gas can be deter-mined by many men by observing the behavior of the safety-lamp flame in the different mixtures. Mine foremen frequently guess the percentage of gas to within 0.1 per cent., making certain allowances to cover the dust-laden atmosphere, in which the test was made. It is not meant by this that anthracite dust is explosive, but that its properties increase the length of a fuel cap on an ordinary oil-burning lamp, which, as Prof. -Young contends, increases in height with the proportion of gas and in-creased temperature. Naphtha or benzine-burning lamps have a hotter flame, and, there-fore, are more sensitive so that a smaller percentage of gas can be detected. Some of the fire bosses in this region some years ago preferred the Koehler lamp, while others did not care to use it in their morning examinations. In 1911, when the experimental mine of the Bureau of Mines at Bruce-ton, Pa., was being prepared to be exploded, a large number of mining men went through it to examine the entries, which were lighted by electricity. While so doing, they saw in the face-return-airway a Koehler or Wolfe lamp, that seemed to he burning with difficulty. An investigation showed that the lamp had been filled to overflowing with naphtha and was generating this surplus gas. This shows how easily we can be

Jan 11, 1919