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By Edmund J. Korber, Donald E. Raab, Frank A. Burns

During the early 1960s, the advent of self- advancing longwall roof supports triggered serious consideration by Bethlehem management to introduce the technique of longwall mining at one of our central Pennsylvania coal mines. Although longwall mining was initially justified as a means to cope with the severe roof conditions at our Mine 32 (Watson, B., 1971), the result of the endeavor has been a consistent and reliable level of coal production, first from Mine 32 and then later from Mine 33, over a period of fifteen years. Longwall production from the Cambria Division has been the mainstay of the low volatile coal required by Bethlehem Steel for steel production. Let us review the events that led to this accomplishment, as well as where we stand today.

Jan 1, 1981

By Henry S. Drinker

(Canal Zone Meeting, November, 1910.) FEW men reach middle life without having had the experience of failure in one or more undertakings; and most of us can look back with gratitude to help or advice given us by friends at critical periods of our lives. If, as men, we ask and take the benefit of such aid, why should we expect our sons to be stronger? A parent can make no greater mistake than to send a boy, however steady and intelligent he may be, off' to school or college, and expect the boy always to cope successfully with all the new conditions and new difficulties that may confront him. This is undoubtedly more the case with a freshman, in his first year at college, than in later years, or than it is with a boy at day- or boarding-school, where the boy receives a greater degree of care and oversight than can be given to the young man entering college; of all periods in life, the youth in his freshman year-fresh from the overshadowing care of home and school-may need judicious advice and timely aid. The change from the restraint of home and school to the freedom of college life is sudden and marked, and it is in this the first year of the boy or young man of 17, 18, or 19 years of age, that some tactful, judicious aid should be near him in his work and course. Some boys go to college so well prepared that they become careless and finally fall behind in their work from over-confidence. Others meet trouble from ambitiously trying to do more than their previous preparation, or physical or mental strength, can sustain. Others fall behind from illness-from injuries-from natural inability to grasp at first, without more aid than comes to them in the regular course of instruction, the higher mathematics-or mayhap the modern languages, or other subjects presented by the advanced curriculum of the present day. When a boy or youth begins to

Jan 1, 1911

By Burt Hartmann

The nation's ever-expanding construction and mining activity has placed an increasing demand upon engineers and geologists to design and construct stable slopes in earth materials-soil and rock. Man's attempt to handle these slope stability problems has been based primarily on practical experience and the resulting theories formulated to explain the phenomena. Too many instances occur when man is faced with a slope stability problem that has not yet been experienced and doesn't lend itself to solution by any existing theory. At this point he must extend himself in using his engineering judgment to arrive at a reasonable and safe design. As past experience has shown, all of the "safe designs" are not really safe. Sometimes they result in embarrassing failures. Measurements provide the key to understanding and controlling natural phenomena. We cannot hope to gain control of the slope stability problem until we understand the causes of slope failure, their behavior with respect to time and their relative magnitudes. Measurements required for an adequate definition of any slope problem must be of the highest reliability because of the importance of decisions which must be based on them. For this reason, direct measurements of movement, shear strength, water pressure, etc. of the unstable mass are preferable to indirect measurements of other physical properties. Movement instruments which can be positioned inside of the slope mass (within boreholes) are among the most useful in diagnosis and/or monitoring of slope movements. The higher the sensitivity and il-measurement precision possible with borehole instruments, the quicker the required information can be obtained and the more exactly may hazardous conditions be observed. A high density of measuring points in a single drill hole is deemed essential for diagnostic purposes. Behavior gradients may thus be obtained. The Pressure Meter (Fig. 1) can be used to measure a relative strength

Jan 1, 1968

By J. T. Ryan

IN making a comparison of mine inspection methods in Europe and the United States, it is necessary to have some basis to start from, which makes this subject rather difficult, as such methods are governed largely by the authority given the inspector by the mining laws. In the United States there are 31 coal producing states and territories and 32 different mining laws under which inspectors operate, as one state-Pennsylvania-has both a bituminous and an anthracite code. Some of these codes are distinctly coal mining codes; others are essentially coal mining but apply also to other mines; several codes are sub-divided referring partly to coal mines and partly to other mines, and a few codes are mainly metal mining but apply in part to coal mining. Having all these different codes in the United States and the departments organized in a variety of different ways, there is of necessity a great difference in inspection methods in this country.

Jan 1, 1926

By George Mixter

MINING, in contrast to manufacturing, deals with a wasting asset. That which is taken out of the ground is gone, the property is depleted to that extent, and will eventually become exhausted of profitable ore. So the life of a mining company is dependent upon the ability of its management to develop improved methods to permit extraction at a profit of the lower-grade ores which remain, to extend by intelligent exploration the limits of its known ore bodies, and to find and acquire new properties to take the place of those that, for one reason or another, are no longer operated. Its history is a story of constant change, of the working out of properties here and the acquisition and development of properties there, to maintain the vitality of the whole. It is a story of estimating with the tools and the knowledge available the location and extent of hidden ore bodies and of devising the means of extracting

Jan 1, 1948

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) No. 488.-Mining engineer, member, technical graduate, married, age 38, desires position of superintendent or assistant superintendent. Has had 15 years' practical experience as miner, millman, machinist, surveyor, engineer, foreman, and superintendent in the West, Southwest, and Mexico. Speaks Spanish. Now employed as superintendent of copper property in Southwest. Can give the best of references. Minimum salary $250. Available after Sept. 1. No. 495.-Member, age 36, married, technical, 10 years'. all round

Jan 12, 1918

By Dever C. Ashmead

COAL companies in the anthracite region are studying various methods of mining that will permit a considerably shorter life of gangway and therefore a decrease in the maintenance charges. Maintenance charges in the upkeep of gangways where the measures are steeply pitching are high due to the excessive cost of the replacement of timbers and the cleaning up of falls. Therefore, if the length of gangway in the coal beds can be decreased and the mining more concentrated, the life of the coal gangways will be decreased and consequently the maintenance charges will be lower per ton of coal produced. Customary practice in the anthracite region is to drive long coal gangways and to work the breasts as the gangway from which they were driven is advanced.

Jan 1, 1925

By E. H. Mohr

AT the McGill concentrator of the Nevada Consolidated Copper Co., all flotation operations have been carried out in Forrester cells since November, 1926. In respect to cost of operation, the new cell has proved to be superior to the Callow, which it supplanted, and its incorporation in the flow sheet has resulted in a marked improvement in the metallurgy. Before citing the advantages of the new machine over the old, it should be explained that the Forrester has not only replaced the Callow, but it has made possible the elimination of a number of tables as well. When Callow cells were in use, table concentration preceded flotation. The ball mill pulp was elevated, by means of air lifts, to roughing Wilfley tables situated two floors directly above the flotation floor. On an intermediate floor were additional tables which cleaned the concentrate from those above. The finished table concentrate constituted approximately 60 per cent. of the total mill production, and contained about 40 per cent. of the recovered copper. The table tailings were returned to the classifiers, the overflow from which went to the flotation cells and the oversize to the ball mills. As soon as the Forrester cells were installed, this tabling operation was discontinued. The ball mill pulp now discharges into the classifiers direct, without the intermediate tabling. It was impracticable to employ the present flow sheet when Callow cells were in use, for the reason that unless the greater part of the heavy mineral was first removed, it accumulated on the mats and adversely affected the flotation operation. By tabling ahead of flotation, it was practicable to maintain the concentrator at 10 to 20 per cent. greater capacity (depending up on the pyrite content of the ore) than was possible by flotation alone. This was due to the necessity for finer grinding in the latter case. Even though the table concentrates contained only 6 to 8 per cent. copper con- tent, the low smelting costs made it advantageous to operate at high mill capacity, at the cost of low grade of product. STANDARD SECTION EQUIPMENT With the old-flow sheet, a standard section consisted of four ball mills and classifiers, one air lift, 20 roughing tables, 10 cleaner tables, 12 primary

Jan 1, 1928

Last spring the suggestion was made that the national engineering societies offer to assist the War Department in the formation of an engineer reserve in the United States Army. The suggestion was brought to the attention of some of the officers of the Army, who commended it and confirmed the belief that the need of such a reserve was a real one; that the European war had distinctly shown that engineers in time of war are required on a scale never before realized and of great varieties of experience. In our own army no adequate provision is made for great numbers of engineers, for although the corps of engineers is composed of men of the very highest professional proficiency in certain lines it is greatly short of the numerical strength that would be immediately required. Acting on this suggestion, the American Society of Civil Engineers, the American Institute of Mining Engineers, the American Society of Mechanical Engineers, the American Institute of Electrical Engineers and the American Institute of Consulting Engineers appointed committees authorized and directed to take such steps as might be advisable to urge the organization of such a reserve corps as part of the. regular army, and so assist in putting the United States in a better condition of prepared-

Jan 10, 1915

Without having asked for it, the writer has apparently been drawn into the discussion regarding relative hoisting capacities which was started by Woodward Iron, egged on by Joe Haller of Cleveland-Cliffs [Mining Engineering, August p. 642] and Axel Kjelgaard [November p. 919], who took exception to Mr. Haller's remarks of tonnage hoisted and avers that they do better in Sweden. It does not appear to the writer that Mr. Haller was inclined to refer to the tonnage hoisted at Cleveland-Cliffs in a manner to imply that they claimed any hoisting record, but rather as a statement that they had hoisted a certain amount of ore during the year 1950. Mr. Haller has been in the mining game long enough to appreciate what Mr. Kjelgaard did not apparently take into consideration, that length of haul, shifts hoisted, nature of ore, method of loading and the many other factors which influence the hoisting cycle make a comparison of tonnages hoisted of two given mines almost an impossibility. Mr. Cheyette sent you .a copy of his letter to Bob Manegold relative to the capacities of the Orient #2 mine. There are several mines around the Country which constantly set up records about which little or nothing at all is ever heard. We cite the Snow Hill Coal Co. mine at Terre Haute, Ind., which has an automatic Nordberg hoist and which hoists 12 tons per trip or 700 tons per hr from 700 ft. This is a counter-weighted installation and a complete cycle is made every 62 seconds or 58 trips per hr. Another mine, The Potash Company of America mine at Carlsbad, N. Mex., has a Nordberg automatic hoist, hoisting eight tons per trip from 1150 ft on a one minute cycle. The materials hoisted in these two mines are ideal for automatic hoisting-they are free flowing so that no hang up is anticipated and hoisting is continuous. Multiplying out the above figures you will find that it is possible to hoist 11,000 tons in two shifts at Snow Hill or over 3 million tons in 300 days per year and over 2 million tons at Potash. Other mines have records which can be pointed to with pride. When a record for one year is established, it doesn't stand too long as here in America the ambition of all the men connected with the operation forces them on to larger tonnages. T. C. WIEDENHOEFER MANAGER MINE HOIST DEPARTMENT NORDBERG MANUFACTNRING CO. MILWAUKEE, WIS.

Jan 1, 1952

By Stanley C. Herold

TWENTY-FIVE years ago no distinction was made between water wells and oil wells except in the nature of the fluid produced. Water wells usually showed no decline in their rate of production; when oil wells showed decline something in the manner of handling them was considered wrong. Both water and oil were believed to be subject to the same physical laws in their underground movement toward the wells. Today a sharp distinction is made between them. Whereas water exists alone in the porous formations at depth, oil is usually accompanied by gas. This mixture does not behave as a liquid alone. It is a frothy, seething mass of foam which approaches and enters the wells. Different physical laws come into play. Twenty-five years ago attention was directed entirely to the well itself; today the well is accepted as a mere hole in the ground, a hole to be equipped properly for efficient service, yet without any value whatever unless it is backed up by a sufficiently prolific reservoir. Then, we were concerned with wells alone, 3000 ft. in depth; now commercial wells and their reservoirs are 10.000 ft. deep. Petroleum engineering concepts have necessarily therefore undergone a change in this last quarter century. What are they today?

Jan 1, 1937

By Eugene F. Poncelet

This paper attempts to analyze the phenomena involved in the fracture of brittle solids by simple compression. Glass squares standing on edge, and compressed between two parallel steel jaws, developed jagged fractures, roughly parallel to the compression. Polarized light disclosed the presence of high local stress concentrations indicating poor contact all along the contact surfaces with the steel jaws. Teszar has shown that partial contact between the jaws and such a compressed solid causes tensile stresses in the free surfaces of the solid normal to the compression. Furthermore, Scoble has shown that in brittle solids fractures are caused by, and develop normally to, a sufficient tensile stress. It follows that such "partial-contact" cracks must be expected. With optically flat jaws and specimens, no "partial-contact" cracks developed. Instead, very smooth cracks vertical to the compression appeared 'upon release of the pressure. Investigation showed that the friction with the rigid steel opposed the return of the glass to its original width, after creeping on the steel as compression built up, thus setting up tensile stresses in the glass surfaces. It was not found possible to eliminate these "release" cracks. Compressed to destruction, such specimens flew to dust. A Microflash photograph taken during the explosive disintegration revealed: (I) oblique parallel fragmentation cracks, 30" off the direction of the compression; (2) transverse forking fragmentation cracks, normal to the former; (3) release cracks parallel to the compression; (4) a disintegration cloud. Given a distribution of submicroscopic cracks of random orientation throughout the glass, Griffith has shown the highest tensile stresses to be located at the tip of the cracks 30" off the direction of the compression. Although the preexistence of such cracks or flaws in unstressed glass is doubtful, they can be generated by the distorting forces set up by the compression itself. Atoms, in a structure held together by Morse-type forces or bonds, have under tension both a stable and an unstable state-of equilibrium. The difference in energy level between these two states is a function of the tension, and this difference must be borrowed from the thermal energy level of the bonds to reach the unstable state and result in a broken bond. As the fraction of the bonds having at any instant a sufficient thermal energy level is a known function of that level, it is possible to determine, in function of the prevailing tension, the fraction of the bonds that are broken. Upon breaking of the bond uniting two atoms at the tip of an advancing crack, the two atoms accelerate away from each other, causing in the solid propagation of a

Jan 1, 1944

By Eugene F. Poncelet

This paper attempts to analyze the phenomena involved in the fracture of brittle solids by simple compression. Glass squares standing on edge, and compressed between two parallel steel jaws, developed jagged fractures, roughly parallel to the compression. Polarized light disclosed the presence of high local stress concentrations indicating poor contact all along the contact surfaces with the steel jaws. Teszar has shown that partial contact between the jaws and such a compressed solid causes tensile stresses in the free surfaces of the solid normal to the compression. Furthermore, Scoble has shown that in brittle solids fractures are caused by, and develop normally to, a sufficient tensile stress. It follows that such "partial-contact" cracks must be expected. With optically flat jaws and specimens, no "partial-contact" cracks developed. Instead, very smooth cracks vertical to the compression appeared 'upon release of the pressure. Investigation showed that the friction with the rigid steel opposed the return of the glass to its original width, after creeping on the steel as compression built up, thus setting up tensile stresses in the glass surfaces. It was not found possible to eliminate these "release" cracks. Compressed to destruction, such specimens flew to dust. A Microflash photograph taken during the explosive disintegration revealed: (I) oblique parallel fragmentation cracks, 30" off the direction of the compression; (2) transverse forking fragmentation cracks, normal to the former; (3) release cracks parallel to the compression; (4) a disintegration cloud. Given a distribution of submicroscopic cracks of random orientation throughout the glass, Griffith has shown the highest tensile stresses to be located at the tip of the cracks 30" off the direction of the compression. Although the preexistence of such cracks or flaws in unstressed glass is doubtful, they can be generated by the distorting forces set up by the compression itself. Atoms, in a structure held together by Morse-type forces or bonds, have under tension both a stable and an unstable state-of equilibrium. The difference in energy level between these two states is a function of the tension, and this difference must be borrowed from the thermal energy level of the bonds to reach the unstable state and result in a broken bond. As the fraction of the bonds having at any instant a sufficient thermal energy level is a known function of that level, it is possible to determine, in function of the prevailing tension, the fraction of the bonds that are broken. Upon breaking of the bond uniting two atoms at the tip of an advancing crack, the two atoms accelerate away from each other, causing in the solid propagation of a

Jan 1, 1944

By Robert Richards

Introduction. WALTER RENTON INGALLS recently gave a very interesting talk before the student mining society of the Massachusetts Institute of Technology. In it he showed the present status of mining as he sees it. In the talk he explained that, while discoveries of great mining districts are still possible, they are being made less and less often; that the great mining companies, although there are large numbers of mines offered for sale, are finding it less and less possible to find new mines that are up to the standard of richness that they wish for purchase. The natural conclusion is that better, cheaper, and more efficient methods of mining, concentrating, and smelting are needed if the lower-grade mines are to be worked at a profit. This is true also if the high-grade mines are to yield their greatest profit. This paper deals only with the concentrating or ore-dressing problem, and gives some thoughts which point towards greater profit. In a paper on The Development of Hindered-Settling Apparatus the writer showed that there were two main lines of work that would lead to greater saving, lower tailing assay, and, therefore, greater profit. The first is the recrushing of middling or tailing products for the saving of the contained values. This is well understood and largely carried out in existing mills. The second is the saving of fine free mineral at the first opportunity. This is a matter less well understood in the mills, and to dwell upon this the present paper is written.

Jan 9, 1913

By Robert S. Williams

NO new ferrous alloys have been produced in the last five or six years that are as outstanding contributions to civilization as were the high-speed steels of the early part of the century or the stainless steels announced at the close of the World War. There have been, however, many developments of major importance having to do either with modifications of existing alloys or with new methods of treatment of older iron or steel alloys. Only a limited number of these new developments can be discussed and their selection does not necessarily imply that these are the most important but merely that they are of general interest rather than perhaps of greater importance in highly specialized fields.

Jan 1, 1939

By F. C. Canney

Geochemical prospecting seeks hidden mineral deposits by sampling for variations in the chemical composition of naturally occurring materials. Usually the samples are of soils and other products of weathering and erosion-surface materials extremely susceptible to contamination by human activities. Except when a survey is conducted well away from populated areas, contamination is an ever-present hazard. The program's success is particularly endangered when the contaminants are the elements sought; if these occur erratically throughout an area, spurious anomalies completely unrelated to mineralized areas can be formed. Evenly distributed contamination can be dangerous too, if it raises the background to such a level that true anomalies can no longer be easily detected. Suppose, for ex- ample, that in an area where the lead background is 20 parts per million the soil over a lead vein contains 1000 ppm of lead. Here the contrast would be 50 to 1, which is very satisfactory for geochemical surveying. Now if 1000 ppm of lead from some source were added evenly to the soil in this area, the contrast would be reduced to about 2 to 1, and the anomaly would no longer be readily detectable because a threshold of significance twice the value of the background is the minimum generally used for interpreting geochemical data.

Jan 2, 1959

By Eugene McAuliffe

SINCE 1917, the bituminous coal industry has surged, violently at times, across the nation's social, industrial and economic foreground. To-day a silent, yet more active, force is working within the industry, and the movement now taking place, if allowed to continue, will cause serious consequences when coal is again wanted at the rate of 550,000,000 tons annually instead of at the rate of 400,000,000 tons, the apparent requirement for 1921. I refer to the shift of tonnage from the highly unionized fields of Pennsylvania, Ohio, Indiana and Illinois to the non-union fields of Pennsylvania, West Virginia, Alabama and certain western states, and to the so-called union fields in Kentucky and Colorado, on which the union saddle rests lightly. This movement, in the absence of the usual winter transportation shortage, is taking place rapidly and will be accentuated if, as is probable, work is suspended in the union mines on March 31 next. This drift of tonnage has been made possible by the unit wage reductions in the non-union fields and by the modification of the so-called conditions that have been saddled on all mines wherever the United Mine Workers have gained a foothold; these changes permitted the first reduction in mine cost, which made possible the securance of contracts; better running time assisted in making further reductions, and the transfer of ton-nage served to increase the unit cost in the field from which it was transferred. This situation not only opposes the highly unionized operation but brings about a transfer of traffic from the roads serving such mines to those that serve in a primary or secondary manner the more favored localities. The net result is evidenced in (a) the migration of union labor to the non-union mines; (b) the deteriora-tion and decadence of union properties; (c) the neces-sary curtailment in the purchase of new equipment and in the maintenance of existing equipment and track facilities on the part of the carriers serving the union fields. This, in turn, when business is restored to normal or to the point above normal that invariably follows an adverse swing of-the business pendulum, will cause (d) a shortage of coal and coal transportation facilities; (e) an era of coal speculative debauchery with exorbitant prices and serious deflection in the matter of quality; (f) a period of labor unrest followed by de-mands for increased wage rates supplemented by a marked loss in individual efficiency, with, resultant strikes, business unrest, and the pressure of new eco-nomic theories. In 1918, the labor status with respect to relative tonnage produced was approximately as follows: pro-duced in highly organized fields, 62 per cent.; produced in partly organized fields, 21 per cent.; produced in unorganized fields, 17 per cent. During the strike of November and December, 1919, the mines that remained at work attained 35 per cento of the nominal production of soft coal, a situation made possible by the migration of union labor to non-union mines and the concentration of the nation's coal trans-portation facilities on the rails of the carriers serving the non-union fields. The history of the efforts made by the carriers to untangle the car scrambling which took place during this period and which sent the self clearing battleship type of car into western territory where it could not be readily unloaded, and the western gondola type of car to New England and the seaboard, is yet painfully recalled. -This confusion proved a serious factor in the coal car shortage that continued throughout the following year. We are drifting toward a similar situation now, propelled by economic forces rather than by a sudden strike.

Jan 1, 1922

By William H. Spice

No devclopment of major importance has been made in the south central fault-line district of Texas during 1939. Four new fields have been discovcred, all of which appear to be of minor importance, with small wells in the Navarro sand, the Taylor marl or the Austin chalk. Drilling along the fault line has not developed any new prospects in the Edwards lime, the most prolific producing horizon of the district. At the close of the year, a few deep tests for lower producing horizons have been projected and should prove to be of interest, and plans are under way for further development of the Pearsall field, which has been under the control of a single company until recently. Production from the 46 producing fields was maintained at 8,460,000 bbl. for the year, a decrease of approximately 400,000 bbl. under 1938. This decrease is due in part to natural decline of production and in part to decreased allowed production. Approximately 55 producing wells were completed on proven acreage in the Darst Creek and Salt Flat fields. No new lease plays were made during the year, although approximately the same amount of land, 600,000 acres, remained under lease during the year. Some geophysical operations of various types were carried on along the fault-line area itself and also in the Edwards plateau and in the area south and southeast of the main fault line.

Jan 1, 1940

By William H. Spice

No devclopment of major importance has been made in the south central fault-line district of Texas during 1939. Four new fields have been discovcred, all of which appear to be of minor importance, with small wells in the Navarro sand, the Taylor marl or the Austin chalk. Drilling along the fault line has not developed any new prospects in the Edwards lime, the most prolific producing horizon of the district. At the close of the year, a few deep tests for lower producing horizons have been projected and should prove to be of interest, and plans are under way for further development of the Pearsall field, which has been under the control of a single company until recently. Production from the 46 producing fields was maintained at 8,460,000 bbl. for the year, a decrease of approximately 400,000 bbl. under 1938. This decrease is due in part to natural decline of production and in part to decreased allowed production. Approximately 55 producing wells were completed on proven acreage in the Darst Creek and Salt Flat fields. No new lease plays were made during the year, although approximately the same amount of land, 600,000 acres, remained under lease during the year. Some geophysical operations of various types were carried on along the fault-line area itself and also in the Edwards plateau and in the area south and southeast of the main fault line.

Jan 1, 1940

V. H. GOTTSCHALK, Rolla, Mo. (written discussion*).-In connection with Mr. Waring's quotation of Urbain's work, attention may be drawn to a remark found in the report of the session of the Société de Chimie Physique,1 held in December, 1909, that, while all blendes contain gallium in larger or smaller quantities, those blendes carrying indium are generally free from germanium, and vice versa. Urbain, furthermore, . expresses his conviction that this behavior, being related to the condi-tions of deposition of the ore, should be an important factor in determining the origin and mode of formation of zinc blende deposits., In. searching the literature for the naturally expected sequel to these remarks, there is found a report on the extraction of germanium from blende, after many months' work, on a commercial scale;2 then a paper3 on some Spanish blendes, all containing cadmium, examined by Urbain's 'method (this paper contains, also, very important work on the com-position and color of blendes, as well as on the occurrence of organic .matter and of inclusions in such blendes), and a second paper on Spanish blendes in general, in which this original point of Urbain's concerning the relative quantities of the three rare elements is taken up.4 Angel del Campo finds that of 68 specimens examined, four only were entirely free of germanium, gallium, and indium;. 38 had small proportions, while 19 were notably, and seven relatively rich in the three rare metals. He found the relative frequency to be: gallium in 60, germanium in, 50, and indium in 38; all three occurred in 29 cases; germanium and gallium together in 18; gallium and indium together in four; germanium and indium together without gallium, in none; four had gallium only, three had germanium only, and one had indium only; in 23 it appeared feasible to extract these elements. Finally, it may be worth mentioning that the discovery of gallium in commercial aluminum5 brought forth two

Jan 1, 1918