Search Documents

By S. F. Emmons

Introductoy.—In view of the fact that an opportunity is to be offered to the members of the Institute present to inspect the recent developments of gold-deposits in the immediate vicinity of Washington it has seemed appropriate that some preliminary description of them should be given which may facilitate that inspection. It would have been a matter of much satisfaction to me to be able to present some general description of the gold-deposits of the Appalachian system ; but I have as yet had no opportunity of personally examining any others than those of Montgomery county, and these are still in their infancy. It is, moreover, a slower and more difficult operation to make geological observations in this region than in the more northern States; for whereas in the latter region the

Jan 1, 1890

By Zavis M. Zavodni, Carl D. Broadbent

During the past 15 years, rock mass structural properties have become acknowledged as the focal point for rock slope design. Re- search into the methods for measuring and incorporating structure into the design effort has taken many directions and has produced a variety of useful techniques. Among the findings at Kennecott has been the realization that structure-controlled instability can be categorized as regressive or progressive depending on the relative geometries of slope and structure and on the strength characteristics of the structures. It was further identified that a failure condition can initiate as regressive and in time become progressive should external stimuli increase or structure characteristics be altered due to extensive displacements. The transition point has been shown to be a useful indicator of the expectable collapse time. This paper defines three fundamental failure types as dictated by structure and offers discussion on the practical value of such a classification to slope design and failure control. Several prominent examples of failures typifying the categories of structure- controlled instability are discussed. An application of f allure prediction based on the regressive-to-progressive transition point is described.

Jan 1, 1983

By John W. Buch

NeaRly 25 years ago operating officials in the northern anthracite field were confronted with the problem of profitably mining virgin beds of thin coal (those 48 in. and under) or destroying them by mining underlying thick beds. To solve this problem costly hand-mining methods were replaced by cheaper mechanical methods, which eliminated the need for the lifting of bottom or the brushing of top in excessive quantities, which was essential if proper height for hand loading1 was to be provided. During this period long-face mining was an outstanding development. In its favor in comparison with any other method were the ease with which undercutting machines could be used, a differential in powder cost of about fifteen cents per ton in favor of this method over mining from a solid chamber or pillar face, and a greater production per day from a single working place, resulting in lower capital expenditures for a given total production, closer supervision and lower transportation cost. The long faces were drilled by jackhammer and undercut by machines. The coal from the cut was loaded into mine cars placed on the gangway road by means of a double-drum mechanical scraper engine and a mechanical V-type scoop. A tugger hoist was used to spot empty cars at the loading point from a supply placed at the operation by an electric mine locomotive. During loading the roof was supported by vertical wooden props paralleling the face. After the loading was completed the scraper engine and the ropes that had been used to propel the scoop in the loading of coal transferred the props to and along the face. A row of unfilled cogs was then built parallel to the new face and about 6 ft. from it. These cogs were usually made 6 by 3 ft., the longer dimension paralleling the face; they were placed on an average at 12-ft. centers. These wooden cogs were left in place and were buried later by falling roof. Attempts to remove them were never successful. When a new long face was started, the cog spacing would be increased to about 20-ft. centers. As successive cuts were made, weight would begin on the cogs, and they

Jan 1, 1940

By John W. Buch

NeaRly 25 years ago operating officials in the northern anthracite field were confronted with the problem of profitably mining virgin beds of thin coal (those 48 in. and under) or destroying them by mining underlying thick beds. To solve this problem costly hand-mining methods were replaced by cheaper mechanical methods, which eliminated the need for the lifting of bottom or the brushing of top in excessive quantities, which was essential if proper height for hand loading1 was to be provided. During this period long-face mining was an outstanding development. In its favor in comparison with any other method were the ease with which undercutting machines could be used, a differential in powder cost of about fifteen cents per ton in favor of this method over mining from a solid chamber or pillar face, and a greater production per day from a single working place, resulting in lower capital expenditures for a given total production, closer supervision and lower transportation cost. The long faces were drilled by jackhammer and undercut by machines. The coal from the cut was loaded into mine cars placed on the gangway road by means of a double-drum mechanical scraper engine and a mechanical V-type scoop. A tugger hoist was used to spot empty cars at the loading point from a supply placed at the operation by an electric mine locomotive. During loading the roof was supported by vertical wooden props paralleling the face. After the loading was completed the scraper engine and the ropes that had been used to propel the scoop in the loading of coal transferred the props to and along the face. A row of unfilled cogs was then built parallel to the new face and about 6 ft. from it. These cogs were usually made 6 by 3 ft., the longer dimension paralleling the face; they were placed on an average at 12-ft. centers. These wooden cogs were left in place and were buried later by falling roof. Attempts to remove them were never successful. When a new long face was started, the cog spacing would be increased to about 20-ft. centers. As successive cuts were made, weight would begin on the cogs, and they

Jan 1, 1940

By Albert Mendelsohn, Charles F. Jackson

The system of stoping described in this paper was first introduced at the Champion mine of the Copper Range Co., Painesdale, Mich., in 1929, and since that time has been developed to a high state of efficiency. The method was devised to overcome some of the objections to the system of horizontal cut-and-fill stoping formerly employed at this mine and has done so successfully. The objections to the old system became more pronounced as the depth of mining operations increased and a change became a matter of necessity. While the combination of conditions encountered at the Champion mine is rather unusual, it is believed that the sublevel system developed there could be employed advantageously at other mines, though certain modifications might be necessary. This paper describes the method and the results obtained through its use, and suggests modifications for making it applicable under quite different conditions from those at the Champion mine. Champion Lode The lode being mined at the Champion mine is the heavily brecciated top of what is known in the district as the Baltic lava flow. The brecciated portion of the lode varies from 6 to 50 ft. in width. Under this breccia is the thinner, tighter, amygdular portion of the lode; under the amygdular portion is the trap footwall. Native copper is found deposited in the rock fragments of the breccia, in the cementing material of the breccia, in the amygdules and in the trappy rock under the amygdular part of the lode. In some places masses of copper many tons in weight extend far into the footwall of the lode. The Baltic lode on Champion property is 8000 ft. long, very straight along the strike, and dips uniformly 70' to the west for 3000 ft. in depth, at which point the dip begins to flatten slightly. The width of the copper-bearing portion of the lode varies from 10 ft. to as much as 80 ft. in a few places; the average width now mined is 17 ft. The lode rock is hard—the standard one-man drilling machines used in the mine drill from 10 to 14 in. per minute when mass copper is not

Jan 1, 1932

By M. E. Volin, F. H. Erbisch, G. M. Wenberg

Bacterial leaching of copper and uranium is practiced under acidic conditions in environments furnishing sulfur and iron. However, many mineral deposits do not have these conditions; the chalcocite and native copper deposits in Michigan's Upper Peninsula are examples. Species of bacteria and fungi isolated previously from samples taken at the White Pine Copper Co. tailings pond and mine, were screened for solubilization of copper from chalcocite ore and flotation concentrate and from native copper jig concentrate. Certain Penicillium species solubilized significant amounts of copper under neutral to slightly acidic conditions in a carbon and nitrogen-enriched medium. Leaching apparently was accomplished by release of metabolites which chelated with the copper. The copper yield was highly dependent upon the medium composition and the concentration of copper in the source material. The standardized procedures which were developed in an attempt to maximize copper yield in leaching times of three to five days are described. This preliminary research indicates a biological leaching process for copper which is different from those in use, but whether it can be applied economically remains to be determined.

Jan 1, 1972

By Max C. Eastman, V. H. Wilhelm

California had a record year in production and drilling activity, but the results have not been sufficient to keep up with the enormous increase in demand due to war activity. During the year, 164 dry wildcats were drilled, 80 dry wells in proved areas, 31 gas wells, and 1158 successful oil-well completions for a total of 1433 wells, compared with a total of 765 in 1942. With new discoveries of only 20,000,000 and production of 283,000,000 bbl. for the year, total reserves of California oil have decreased more than 250,000,000 bbl. However, revised estimates of the reserves of old fields indicate an increase in the state's reserves of I00,000,000 barrels. The completion of 1158 wells has served only to maintain the maximum efficient daily rate of production at 800,000 barrels. There is evidence in many fields that oil is being withdrawn too rapidly to obtain the maximum recovery, and more rapidly than is conducive to good production practice. Statistics for 1943 as compared with I942 are shown in the table in the next column, Supply and Demand Steadily mounting needs of the military forces and increased industrial consumption raised total demand for all petroleum products on the Pacific Coast to 914,000 bbl. daily in 1943. That all-time record demand was 149,ooo bbl. daily higher than in 1942 and 214,000 bbl. daily above 1941 demand. Despite restrictions due to shortages of critical material, crude-oil production was boosted from 680,000 bbl. daily in 1942 to 779,000 bbl. daily in 1943, the highest level in 15 years. However, the new crude supply plus natural gasoline production and imports from other states totaled only 840,000 bbl. daily, leaving a deficiency between supply and demand of 74,000 bbl. daily. That shortage had to be made up by withdrawals from inventories, which had been steadily depleted during the previous four years. Aboveground reserves, which totaled 159,574,000 bbl. on Jan. I, 1939, were down to ~8.000,000, bbl. at the end of 1943. Significantly enough, the greater part of that decrease occurred during the last six months of I9437 when more than 23,000,000 bbl. was taken from inventories of both crude and products. Although the size of total inventories on Dec. 31, 1943 might appear substantial, about 65 per

Jan 1, 1944

By Max C. Eastman, V. H. Wilhelm

California had a record year in production and drilling activity, but the results have not been sufficient to keep up with the enormous increase in demand due to war activity. During the year, 164 dry wildcats were drilled, 80 dry wells in proved areas, 31 gas wells, and 1158 successful oil-well completions for a total of 1433 wells, compared with a total of 765 in 1942. With new discoveries of only 20,000,000 and production of 283,000,000 bbl. for the year, total reserves of California oil have decreased more than 250,000,000 bbl. However, revised estimates of the reserves of old fields indicate an increase in the state's reserves of I00,000,000 barrels. The completion of 1158 wells has served only to maintain the maximum efficient daily rate of production at 800,000 barrels. There is evidence in many fields that oil is being withdrawn too rapidly to obtain the maximum recovery, and more rapidly than is conducive to good production practice. Statistics for 1943 as compared with I942 are shown in the table in the next column, Supply and Demand Steadily mounting needs of the military forces and increased industrial consumption raised total demand for all petroleum products on the Pacific Coast to 914,000 bbl. daily in 1943. That all-time record demand was 149,ooo bbl. daily higher than in 1942 and 214,000 bbl. daily above 1941 demand. Despite restrictions due to shortages of critical material, crude-oil production was boosted from 680,000 bbl. daily in 1942 to 779,000 bbl. daily in 1943, the highest level in 15 years. However, the new crude supply plus natural gasoline production and imports from other states totaled only 840,000 bbl. daily, leaving a deficiency between supply and demand of 74,000 bbl. daily. That shortage had to be made up by withdrawals from inventories, which had been steadily depleted during the previous four years. Aboveground reserves, which totaled 159,574,000 bbl. on Jan. I, 1939, were down to ~8.000,000, bbl. at the end of 1943. Significantly enough, the greater part of that decrease occurred during the last six months of I9437 when more than 23,000,000 bbl. was taken from inventories of both crude and products. Although the size of total inventories on Dec. 31, 1943 might appear substantial, about 65 per

Jan 1, 1944

PRACTICAL PROBLEMS AND BASIC PRINCIPLES ranging from ore testing to cost estimation get a working over from top men in the minerals beneficiation field. The Minerals Beneficiation Division developed this symposium for presentation at the 1953 Los Angeles General Meeting to assist the many people who think that having a new plant necessitates a lot of trouble and dismay. The papers and free discussion from the floor give ways and means of approaching a new plant that will relieve the strain on the organization, if adequate attention is put on the program before work begins - that is if thought is given to the program itself, before tackling the actual mill design.

Jan 9, 1953

By J. A. Woolf, E. S. Leaver

THE purpose of this paper is to describe, in a general way, gold-dredging operations in California, with particular reference to unusual features, including types of deposits and recent attempts to improve the recovery of the gold. Dredging Areas The gold-bearing formations that traversed the western slope of the Sierra Nevadas for a north and south distance of some 300 miles furnished the immediate source of the gold found in most of the placer deposits of California. Erosion through a long period carried the gold, together with various forms of partly disintegrated material, to lower elevations and formed placer deposits. Through the classifying action of water in motion, the coarser gold and heavier material of various kinds were - deposited relatively near the source; consequently, in the higher mountain country, old river channels were worked feverishly during the early California gold-rush days because of their high gold content. With the working out of these known high-grade channels, and from the knowledge thus obtained of prehistoric stream beds, drift mining was started and flourished until about 1890. Even today many drift mines are operating with the objective of opening other old Tertiary river channels that have been covered by volcanic flows. Adjacent to these areas, which contained relatively high gold values in the older river channels, smaller particles of gold, gravel, and debris were deposited along the sides of the former stream beds and on the adjoining flat areas, thus forming the large placer deposits, which were worked principally by hydraulic mining. Following the course of the ancient rivers and of the present drainage system to the lower edge of the foothill country, extensive areas of alluvial

Jan 1, 1937

By Thomas T. Read

The purpose of the following research, as originally planned, was to investigate the influence of temperature upon the plate-amalgamation process. In order to consider the amalgamation process intelligently, it was first necessary to learn the nature of an amalgam. In the performance of this task it was found necessary to consult a large volume of literature and to perform experimental investigations. The conceptions of the nature of amalgams thus obtained have so important a bearing on the amalgamation-process as a whole, as well as upon the possible influences of temperature, that it was advisable to include them in the treatment of the subject. The broader title is therefore used, even though some features of the amalgamation process have been treated very briefly and others entirely omitted, there being nothing new to present regarding them and their development not required for a clear presentation of the matter in hand. I. Historical Introduction. Gold was one of the earliest metals known to man. Occurring in the metallic state, it could be picked up in nuggets or mashed, as gold dust, from the sand and gravel of streams. Interestiag descriptions of the processes employed in early times for the recovery of gold may be found in Pliny's Natural History and in the treatise by Agricola on ores and minerals. But little progress in the treatment of the ores of gold mas possible until efficient crushing machines were devised. This want was supplied by the introduction, about the beginning of the sixteenth century, of the stamp-mill to treat the ores of Saxony. Blanket-strakes, or similar devices, were used to catch the

Jan 1, 1907

By Henry M. Howe

Many direct processes have been proposed for the treatment of oxidized ores of copper by reducing the copper oxide to the metallic state, and by separating it from its impurities by a subsequent fusion. The radical objection common to all the methods which have come to my notice, except those in which sulphur plays the prominent part, is that the very deoxidizing agent which effects the reduction of the copper oxide, inevitably reduces at the same time a very considerable part, if not the whole, of the iron which almost invariably accompanies copper in its ores. The result is that, when the ore is subsequently fused, a very great quantity of the already reduced iron separates from the slag along with the copper, alloying with it, and necessitating costly subsequent operations for its separation. Thus, at Perm, in the Urals," the product of the fusion of ferrnginous copper oxides is a mixture of one hundred and fifty-tive parts of highly cupriferous pig iron with two hundred and fire parts of very impure and ferruginous black copper, containing Pome 10 per cent. of' carbon and iron, though free from sulphur, and of course very difficult to refine. If, in order to avoid this reduction of iron to the metallic state, the reducing action be made feebler, it inevitably results that a considerable part of the copper as well escapes deoxidation; and, consequently, the slags are so rich that it becomes necessary to treat them subsequently in order to recover the copper which they contain. Thus,. in treating native copper, at Lake Superior, where the reducing action is purposely made feeble in order to prevent the deoxidation of the iron, the slags from the first fusion of the ore carry so much copper as to render it imperative to treat them again, which is done in a cupola. And yet, in spite of so far weakening the reducing action as to cause a notable slagging of the copper, a very considerable reduction of iron actually takes place. These are the two dangers which threaten the smelter of oxidized copper ores. If he wishes to avoid slagging his copper, he must have so strong a deoxidizing action as to reduce a great deal of his

Jan 1, 1879

By Dale A. Augenstein, S. C. Sun

A primary concern in the solution of any solid waste disposal problem is the characterization of the material. In the past, available methodology for the determination of coal refuse characteristics has been severely limited by the inseparable combination of organic and inorganic matter of which the refuse is comprised. The recent development of an electronic, low temperature asher which removes the organic material without alteration of the inorganic constituents has opened new areas of coal and coal refuse research. This study deals with the development of methodology for the characterization of Pennsylvania anthracite refuse through utilization of the low temperature asher. Seven samples of anthracite refuse were examined for verification of the methodology developed and information concerning the characteristics of the refuse.

Jan 1, 1975

By B. H. Sage

VARIATIONS in the composition of the liquid phase of natural reservoirs which are continuous through significant ranges in elevation have been noted by petroleum technologists. In general, there is a greater gas-oil ratio and the gravity of the oil is higher in production from the upper parts of the formation. In the present paper the possible changes in composition with elevation which would result from the attainment of thermodynamic equilibrium in a uniform gravitational field have been evaluated for a naturally occurring hydrocarbon liquid, a binary hydro-carbon liquid phase and a binary hydrocarbon gas. The results indicate a progressive decrease in the mole fraction of the components from methane through the butanes with increasing depth, accompanied by a corresponding increase in the amount of the heavier components making up the system. The magnitude of these variations is perhaps insufficient to explain completely the variations in the properties of the liquid phase that are encountered at various elevations within a particular producing horizon. However, the changes are significant and the treatment presents an example of the application of thermodynamic data to the evaluation of the properties of hydrocarbon fluids under the conditions approaching those encountered in natural reservoirs.

Jan 1, 1938

By Albert J Hoskinson

Progress on the earth depends to a large extent upon the rapid interchange of ideas and commodities between the various nations of the world. The smooth flow of commerce, by which these ideas and commodities move, is accelerated by accurate and complete maps of the various land and water areas of the earth. The production of accurate maps depends upon a complete knowledge of the figure and dimensions of the object to be charted, therefore a knowledge of the shape of the earth is a prime necessity for accurate charting purposes. Gravity observations were first undertaken to aid in determining the shape of the earth so that the geodetic surveys of its land and water areas might be more accurately connected to form an undistorted map. A large part of the earth's surface is water and it is therefore necessary to get gravity values at sea as well as on land before a complete and accurate figure of the earth can be determined. Dr. F. A. Vening Meinesz, of Holland, was the first scientist to perfect a pendulum instrument that would accurately measure gravity at sea. He had previously developed a multiple pendulum apparatus for measuring gravity upon swampy and unstable land areas in Holland and it was therefore quite natural that he should adapt the instrument to give accurate results upon a still more unstable support, the surface of the sea. His instrument as perfected gives satisfactory results when mounted in gimbals on any vessel where the roll and pitch are not more than about 5" and where the vibrations from rotating machinery and wave action are not large enough to cause the pendulums to shift on the knife-edges. This degree of stability can be obtained on surface craft only in protected waters or on very calm days. Therefore, Dr. Meinesz mounted his instrument in a submarine so that he could submerge below the disturbed surface waters and get the desired stability in nearly any kind of weather by simply diving to greater depths. Most of the gravity-at-sea work has been done with a Meinesz instrument and a very large number of the observations have been made by Dr. Meinesz himself. He has occupied nearly 1000 sea, stations and probably has traveled as many miles by

Jan 1, 1940

By Albert J. Hoskinson

Progress on the earth depends to a large extent upon the rapid interchange of ideas and commodities between the various nations of the world. The smooth flow of commerce, by which these ideas and commodities move, is accelerated by accurate and complete maps of the various land and water areas of the earth. The production of accurate maps depends upon a complete knowledge of the figure and dimensions of the object to be charted, therefore a knowledge of the shape of the earth is a prime necessity for accurate charting purposes. Gravity observations were first undertaken to aid in determining the shape of the earth so that the geodetic surveys of its land and water areas might be more accurately connected to form an undistorted map. A large part of the earth's surface is water and it is therefore necessary to get gravity values at sea as well as on land before a complete and accurate figure of the earth can be determined. Dr. F. A. Vening Meinesz, of Holland, was the first scientist to perfect a pendulum instrument that would accurately measure gravity at sea. He had previously developed a multiple pendulum apparatus for measuring gravity upon swampy and unstable land areas in Holland and it was therefore quite natural that he should adapt the instrument to give accurate results upon a still more unstable support, the surface of the sea. His instrument as perfected gives satisfactory results when mounted in gimbals on any vessel where the roll and pitch are not more than about 5" and where the vibrations from rotating machinery and wave action are not large enough to cause the pendulums to shift on the knife-edges. This degree of stability can be obtained on surface craft only in protected waters or on very calm days. Therefore, Dr. Meinesz mounted his instrument in a submarine so that he could submerge below the disturbed surface waters and get the desired stability in nearly any kind of weather by simply diving to greater depths. Most of the gravity-at-sea work has been done with a Meinesz instrument and a very large number of the observations have been made by Dr. Meinesz himself. He has occupied nearly 1000 sea, stations and probably has traveled as many miles by

Jan 1, 1940

By Jesse Betterton

IN the Parkes process of lead refining, after desilverization has been completed by means of zinc additions, there will remain in the lead from 0.5 to 0.6 per cent zinc. At this stage in the refining practically all impurities are reduced to refined lead specifications except zinc and antimony. All excess of copper and nearly all the arsenic goes out with the silver. Silver remaining should not exceed 0.1 oz. per ton. It thus remains only to remove zinc and antimony to produce refined lead. The older practice was to complete refining by means of oxidation processes in reverberatory furnaces. Essentially this consisted of heating the lead to 1200° to 1300° F. and allowing it to come in contact with a considerable excess of air passing through the furnace, or accom-plish the same result by blowing the lead with steam by means of pipes introduced for that purpose, at the same time allowing air to enter the furnace. Usually some procedure involving alternate oxidation and reduction with fine coal or coke was employed in order to reduce the weight of dross or skim finally removed from the furnace. This practice had many elements of weakness in that the main flow of lead, after the preceding expensive operations had been performed, and the whole refining process nearly completed, was subjected to an operation at a comparatively high temperature, which involved much lead loss if the furnaces were not on bags, and the production of 3 to 5 per cent of the weight of the lead as dross or skim, which had to be resmelted and the lead either refined or produced as antimonial lead. In addition, the operating expense of the process was a considerable item. The, process of dezincing with chlorine was developed as a substitute for the foregoing described oxidation process, and finally resulted in such advantages as nearly equal operating costs, a practical elimination of the lead loss, and the direct production of a very valuable byproduct, zinc chloride, that may be sold as such or retreated for its zinc and chlorine contents, both of which can be reused in the refining processes.

Jan 1, 1933

By H. M. Howe

(Read at. the Lake George Meeting, October, 1878.) MANY direct processes have been proposed for the treatment of oxidized ores of copper by reducing the copper oxide to the metallic state, and by separating it from its impurities by a subsequent fusion. The radical objection common to all the methods which have come to my notice, except those in which sulphur plays the prominent part, is that the very deoxidizing agent which effects the reduction of the copper oxide, inevitably reduces at the same time a very considerable part, if not the whole, of the iron which almost invariably accompanies copper in its ores. The result is that, when the ore is subsequently fused, a very great quantity of the already reduced iron separates from the slag along with the copper, alloying with it, and necessitating costly subsequent operations for its separation. Thus, at Perm, in the Urals,* the product of the fusion of ferruginous copper oxides is a mixture of one hundred and fifty-five parts of highly cupriferous pig iron with two hundred and five parts of very impure and ferruginous black copper, containing some 10 per cent. of carbon and iron, though free from sulphur, and of course very difficult to refine. If, in order to avoid this reduction of iron to the metallic state, the reducing action be made feebler, it inevitably results that a considerable part of the copper as well escapes deoxidation ; and, consequently, the slags are so rich that it becomes necessary to treat them subsequently in order to recover the copper which they contain. Thus, in treating native copper, at Lake Superior, where the reducing action is purposely made feeble in order to prevent the deoxidation of the iron, the slags from the first fusion of the ore carry so much copper as to render it imperative to treat them again, which is done in a cupola. And yet, in spite of so far weakening the reducing action as to cause a notable slagging of the copper, a very considerable reduction of iron actually takes place. These are the two dangers which threaten the smelter of oxidized copper ores. If he wishes to avoid slagging his copper, he must have so strong a deoxidizing action as to reduce a great deal of his * Rivot, Prineipes Généraux du Traitement des Minerais Métalliques, i, p. 79.

Jan 1, 1879

By J. P. Witherow

Mr. BIRKINBINE's description of the bad working and sudden chilling of the Warwick Furnace last summer, seems to me quite phenomenal in blast-furnace practice. During my connection with the management of blast furnaces for many years, in the anthracite, cake, and raw-bituminous coal districts, such a me has never come under my notice. It seems to me that the scaffold in the zone of fusion could not have established itself (so that the whole power of the engines, with a blast pressure ranging from 12 to 18 pounds per square inch, could not penetrate), unless the furnace was previously badly scaffolded and bridged in some of its upper sections, from 15 to 30 feet above the hearth level, either in the zone of chemical action or the beginning of the zone of fusion. Such a 'barrier to the upward gaseous currents would cause a suspension of combustion which may have superinduced the scaffold that is assumed to have existed in the zone of fusion. It is difficult to conceive that an agglomerated mass almost across the section of the lower bosh should have formed all at once, if the furnace was free and porous for the reaction of the gaseous currents, above. Therefore, I think, the Warwick furnace was by no means in as free, open, and fine internal condition at the time the trouble commenced as the description of its regular working would lead us to suppose. I do not question the accuracy of the statements relative to the output of iron, etc I merely claim that the phenomenta, as described, could not have been almost instantaneously developed, unless there had been an incipient scaffold and lodgment above the zone of fusion. I would state my hypothesis to be that the stock lodged or collected in some of its upper sections during fie process of blowing-in, on which, as a basis, more or less accumulations may .have lodged, and thus, indirectly, caused the formation of the suc-

Jan 1, 1881

THE paper on "Cross-cuts in Coal Mining," by J. J. Rutledge (published in MINING AND METAL-LURGY, February, 1927, p. 64) was brought up for discussion at the annual meeting, where the follow-ing comments were made T. D. Thomas (Lehigh Coal & Navigation Co., Lansford, Pa.) : This question has caused me a lot of worry, not in the particular district in which I am, but throughout other districts. There are always several angles to consider. If you are in a hurry to push development work, you might increase the distance between cross-cuts from 60 to 350 ft., but if you have a 40-ft. chain pillar every 60 ft. it will cut down your entry driving a whole lot. Looking at it from the ventilation angle, I agree that too many cross-cuts in entries are bad things. You have a tremendous amount of leakage, and I have seen currents starting out with 45,000 cu. ft., and after passing about 30 or 40 cross-cuts the current has dwindled down to about 18,000 or 15;000 cu. ft. The result is that the question of putting in auxiliary fans is raised. That involves several points into which I do not want to go too far, but I am in favor of not getting in too many cross-cuts, putting them in only where they are necessary: I think the state mining laws are wrong in a number of places on that, and that when you finish with a cross-cut it should be in the room. It should be well sealed on an entry. There are several ways of tightening up the cross-cuts so as not to have the great amount of leakage and wastage of: air that we now have. 'I prefer tile stopping; other people prefer cement or brick, but there is a big fac-tor to all mines, saving the mine. I checked up on the number of fans in the anthracite region and found there are 651. That was derived from the state report of 1921, and it enabled me to compute from the power the weight of the air. In the anthracite region of Pennsylvania we put in 9 tons of air to every ton of coal we get out. Tracing that back again and taking the Government's figures which they made some time ago, I found but 20 per cent of the air got to the faces where it was actually needed. That is a tremendous big loss and shows a possibility for saving, money for the various coal companies. Chairman Rice: I think what Mr. Thomas refers to was an investigation by R. Y. Williams, of the Bureau of Mines in Illinois, where a study was made of 100 typical mines, and, speaking off-hand, my recollection is that we found as little as 15 per cent of air reached the faces in one of the mines and another was as much as 50. That seems to be a reflection on the type of stoppings and general ventilation scheme.

Jan 3, 1927