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The following correspondence relating to a paper bearing the above title, presented by J. F. Wolff, at the New York meeting in February, 1917, and published in the Transactions, Volume LVI, page 142, has passed between the author of the paper, and Mr. Anson G. Betts, and is interesting, although it was received much too late for incorporation in its proper place in Volume LVI. ANSON CT. BETTS, Asheville, N. C.-1. I should like to ask Mr. Wolff if he finds-from analysis of the iron formation and of the iron ore, and from the relative amounts of each in each unit area of the formation, unleached and after leaching, that the iron remains entirely insoluble and the total quantity still remains present; or whether he finds that some of the iron is removed, or possibly even added by deposition from the water passing through the formation. 2. The water that passed into the iron formation had to go somewhere; was it absorbed by underlying formations through hydration, or, after passing through the ore formation, did it come to the surface in springs at a lower elevation, or how did it escape from the ground? 3. I should like to ask Mr. Wolff whether he finds that the iron formation in the sedimentary series does not, come next to the quartzites and generally between the quartzites and slates. J. F. WOLFF, Duluth, Minn.-1. In common with others, you appear to have some hesitancy in accepting the fact of the removal, by solution, of the enormous quantity of silica which has been leached out of portions of the Biwabik iron formation, thus forming orebodies of merchantable iron ore. I believe that even Dr. Waldemar Lindgren once hesitated to accept this fact. However, the evidence is so simple and absolutely conclusive that the fact is established beyond all question. At the contact of orebodies with their rock walls, the bands of iron ore in the orebody can be seen in contact with the corresponding bands of original iron oxide in the rock wall, and the chert layers in the rock wall can be seen to give place to fine granular material (fine silica and iron oxide) and pore space. This is especially noticeable where slumping at the rock walls his not been so great as to displace the layers in the orebody from their contact with their corresponding layers in the rock wall.

Jan 9, 1918

By J. R. Slotemaker

As successfully pilot-tested at a quarry producing limestone for a large cement plant, swiftly flowing streams of rock enter the Gromax Selector. They are electronically scanned while in motion and light reflection data flashed to logic circuits. The logic circuits compute the total light deviations in each rock as it passes the scanner. Thus, a rock with striated or spotted impurities can be rejected or accepted on the basis of its proportional content. The actual case history of this equipment's development at a limestone quarry in the Southeast serves to illustrate its general area of usefulness.

Jan 1, 1964

By E. A. Anderson, W. M. Peirce

Deflection in a corrugated roofing sheet under load may be considered to take place in two stages; an initial bending of the sheet under the load and a slow, permanent flow or creep under continued application of the load. Stresses great enough to produce permanent set when prolonged may produce apparent elastic deformation when applied for only a brief interval. It is impossible to set a time limit on the duration of stress in actual roof installations. Roofs in industrial locations where dust accumulations are heavy, as in cement plants, are often loaded continuously with

Jan 1, 1929

By W. M. Peirce, E. A. Anderson

Deflection in a corrugated roofing sheet under load may be considered to take place in two stages; an initial bending of the sheet under the load and a slow, permanent flow or creep under continued application of the load. Stresses great enough to produce permanent set when prolonged may produce apparent elastic deformation when applied for only a brief interval. It is impossible to set a time limit on the duration of stress in actual roof installations. Roofs in industrial locations where dust accumulations are heavy, as in cement plants, are often loaded continuously with

Jan 1, 1929

By Frederic Benard

The treatment of Balbach-Thum slimes at Copper Cliff by the Ontario Refining Co, is of interest because it differs considerably from methods usually employed for the recovery of fine gold from parting-plant slimes. Owing to the comparatively high percentages of palladium and platinum, wet methods are used to remover the greater proportion of these metals before electrolytic refining in the Wohlwill cells. The Plant The platinum-metals department, Wohlwill room, and gold-melting room extend along the north side of the silver refinery and are separated from the parting plant by a glass partition (Figs. 1 and 2). The platinum-metals department resembles a laboratory built on a large scale, with the various pieces of equipment laid out on terraces to facilitate handling. Because of the corrosive nature of the solutions, chemical stoneware is used throughout. Elevation of acids is accomplished by means of Mariotte bottles. On the top level are three steam-jacketed stoneware kettles of 50-gal. capacity, also a packed tower. One kettle is used for digesting the slimes while the remaining kettles are used for precipitating the gold. The dissolver is equippcd with a treated concrete hood, which is connected to the flue system. Gases are drawn off through the packed tower by means of a 6-in. stoneware exhaust fan. A 15 per cent solution of sodium carbonate is continually circulated through the tower. On the intermediate level are two suition filters, one for removing silver chloride and the other for the gold sand. The filter medium consists of an asbestos pad covered with a filter paper on which is a layer of twill. On the bottom level are two rectangular cementation tanks, 24 by 48 by 24 in. deep, and a suction filter used for removing the platinum-metal concentrates. The circulating pump for the packed tower is also here. Suction is provided by a vacuum pump having a capacity of 8 cu. ft. at 20-in. vacuum.

Jan 1, 1944

By Frederic Benard

THE treatment of Balbach-Thum slimes at Copper Cliff by the Ontario Refining Co, is of interest because it differs considerably from methods usually employed for the recovery of fine gold from parting-plant slimes. Owing to the comparatively high percentages of palladium and platinum, wet methods are used to remove the greater proportion of these metals before electrolytic refining in the Wohlwill cells. THE PLANT The platinum-metals department, Wohlwill room, and gold-melting room extend along the north side of the silver refinery and are separated from the parting plant by a glass partition (Figs. 1 and 2). The platinum-metals department resembles a laboratory built on a large scale, with the various pieces of equipment laid out on terraces to facilitate handling. . Because of the corrosive nature of the solutions, chemical stoneware is used throughout. Elevation of acids is accomplished by means of Mariotte bottles. On the top level are three steam-jacketed stoneware kettles of 50-gal. capacity, also a packed tower. One kettle is used for digesting the slimes while the remaining kettles are used for precipitating the gold. The dissolver is equipped with a treated concrete hood, which is connected to the flue system. Gases are drawn off through the packed tower by means of a 6-in. stoneware exhaust fan. A 15 per cent solution of sodium carbonate is continually circulated through the tower. On the intermediate level are two suction filters, one for removing silver chloride and the other for the gold sand. The filter medium consists of an asbestos pad covered with a filter paper on which is a layer of twill. On the bottom level are two rectangular cementation tanks, 24 by 48 by 24 in. deep, and a suction filter used for removing the platinum-metal concentrates. The circulating pump for the packed tower is also here. Suction is provided by a vacuum pump having a capacity of 8 cu. ft. at 20-in. vacuum.

Jan 1, 1938

By J. J. Kramer, W. A. Tiller, G. F. Bolling

THE axial orientations of columnar crystals in unidirectionally solidified ingots of zone-refined zinc and tin have been examined using the techniques recently described by us.' Both metals had an initial purity of 99.999+ pct before zone refining and satisfied all qualitative guides for very high purity after zone refining. Fig. 1 presents the orientations of the columnar crystals for tin and zinc, respectively. For tin, there is a preference for grains growing in the [I101 direction, i.e., the dendrite direction.' For zinc, a weak preference for the [0001] direction is seen (a random population in the unit triangle would give equal density on either side of the 60-deg circle centered on [0001]).' There was no apparent evidence for dendritic growth in either metal. These results, and those previously reported,' confirm the recent investigation by Hellawell and Herbert of casting textures observed for zone-refined lead, zinc, and tin.4 The preferred casting orientations for these metals in both the impure and zone-refined states are given in Table I. In the experiments on zone-refined lead,' it was shown that two separate textures existed: a preferred (111) nucleation texture existed at the chill surface and a preferred (111) texture developed during solidification. Either effect is sufficient to produce the result recorded in Table I. Similarly the results recorded for tin and zinc may be attributable to either a preferred nucleation or a preferred growth phenomenon and additional experiments are required to separate these two possible explanations. Hellawell and Herbert' attribute their results to a preferred growth process and account for it on the basis of a "layer-growth" model proposed much earlier by one of the present authors.5 An equally satisfactory growth model would be that based upon anisotropic surface energies. However, both of these growth models would indicate that the preferred growth direction for very pure metals should be normal to the plane of closest packing in the metal. This is consistent for zinc but, contrary to the conclusion of Hellawell and Herbert, it is not consistent for tin since here the (100) is expected to exhibit a greater density of packing than the (110). Although tin is expected to exhibit an anisotropy of thermal conductivity, we would expect the thermal conductivity to be the same in the [1101 as the [l00]

Jan 1, 1963

By Peter McKellar

The district around Bag bay in Shoal lake, meat of Lake of the Woods, in the Ontario western gold-fields, is attracting considerable attention at the present time as a gold-producer. A large number of gold-bearing veins have been prospected and mined to a considerable extent in the locality. On the whole they make a fair showing, considering the work done ; and some are undoubtedly rich—the Mikado, for instance. The principal mining companies that have been operating here are the Yum-Yum, Ontario Limited, Cornucopia, Engledue Concession, Tycoon, Toronto and Western and Mikado Cos. I will confine my remarks chiefly to the three companies last

Jan 1, 1900

By W. M. Mobley

The coal industry in Alabama, centered in Birmingham, has pioneered coal-bene-ficiation practice in the United States. The nature of the coal seams and mining methods employed have necessitated use of equipment and methods best adapted to the local conditions. Although all of the 30 or more coal seams now being mined in the state receive beneficiation, only the three most important producers of coking coals, the Pratt, Mary Lee and Black Creek, are discussed in detail. Nature of the seams, washability characteristics and equipment used are given as examples of the extent of work and progress in this field. The coal seams in Alabama are relatively thin and pitching, making mining difficult and expensive. Most of them are characterized by thin partings of rock or shale in the seam itself, as well as laminations of bone and rash. Mechanical mining methods have increased the occlusions from roof and floor to such an extent that nearly all the coal mined in the state must receive some treatment before it can be put on the market. During the year ending Sept. 30, 1943,' 18,129,792 tons of coal were mined in the state and 14,364,177 tons, or 79.2 per cent, received treatment. Excluding from the total the 1,223,014 tons produced by small wagon mines and the hand-picked lump coal, the amount re- ceiving beneficiation would be more than 90.00 per cent. This is, by far, greater than in any other coal-producing state. The earliest record of coal beneficiation in Alabama was the installation in 1890 of an experimental Lurig washer by Alexander Cunningham, for the Sloss Iron and Steel Co. at its blast furnace in Birmingham.2 In 1894 the Jeffrey Manufacturing Co. introduced the English Robinson washer, a combination of a hydraulic classifier and centrifugal machine. Erskine Ramsay, who has contributed so much to the coal industry, saw its possibilities as well as its mechanical defects and soon had his inventive mind at work. He added a sludge tank of his own design, and many Robinson-Ramsay washers were installed in Alabama and other states. The Stewart jig appeared in 1900, followed by the Montgomery jig in 1910 and both have found extensive use. Increased interest in this field led to new designs, such as the American, Elmore, Burke and Faust. The first Baum-type Norton jig was operated in 1930 and within the last five years six large installations of this type have been made by the McNally-Pitts-burg, Jeffrey and Link-Belt Companies. Wet-washing tables were introduced in 1922 but not extensively used until recently. The two most popular types are the Deister-Overstrom and Deister Plat-O. The coal-cleaning equipment used in Alabama has been relatively simple, yet efficient, but as the amount of impurities in the raw coal has been increased by mechanical mining and labor costs have become higher, much interest has been shown in sand cones, froth flotation and

Jan 1, 1947

By W. M. Mobley

The coal industry in Alabama, centered in Birmingham, has pioneered coal-bene-ficiation practice in the United States. The nature of the coal seams and mining methods employed have necessitated use of equipment and methods best adapted to the local conditions. Although all of the 30 or more coal seams now being mined in the state receive beneficiation, only the three most important producers of coking coals, the Pratt, Mary Lee and Black Creek, are discussed in detail. Nature of the seams, washability characteristics and equipment used are given as examples of the extent of work and progress in this field. The coal seams in Alabama are relatively thin and pitching, making mining difficult and expensive. Most of them are characterized by thin partings of rock or shale in the seam itself, as well as laminations of bone and rash. Mechanical mining methods have increased the occlusions from roof and floor to such an extent that nearly all the coal mined in the state must receive some treatment before it can be put on the market. During the year ending Sept. 30, 1943,1 18,129,792 tons of coal were mined in the state and 14,364,177 tons, or 79.2 per cent, received treatment. Excluding from the total the 1,223,014 tons produced by small wagon mines and the hand-picked lump coal, the amount re- ceiving beneficiation would be more than 90.00 per cent. This is, by far, greater than in any other coal-producing state. The earliest record of coal beneficiation in Alabama was the installation in 1890 of an experimental rig washer by Alexander Cunningham, for the Sloss Iron and Steel Co. at its blast furnace in Birmingham.* In 1894 the Jeffrey Manufacturing Co. introduced the English Robinson washer, a combination of a hydraulic classifier and centrifugal machine. Erskine Ramsay, who has contributed so much to the coal industry, saw its possibilities as well as its mechanical defects and soon had his inventive mind at work. He added a sludge tank of his own design, and many Robinson-Ramsay washers were installed in Alabama and other states. The Stewart jig appeared in 1900, followed by the Montgomery jig in 1910 and both have found extensive use. Increased interest in this field led to new designs, such as the American, Elmore, Burke and Faust. The first Baum-type Norton jig was operated in 1930 and within the last five years six large installations of this type have been made by the McNally-Pitts-burg, Jeffrey and Link-Belt Companies. Wet-washing tables were introduced in 1922 but not extensively used until recently. The two most popular types are the Deister-Overstrom and Deister Plat-O. The coal-cleaning equipment used in Alabama has been relatively simple, yet efficient, but as the amount of impurities in the raw coal has been increased by mechanical mining and labor costs have become higher, much interest has been shown in sand cones, froth flotation and

Jan 1, 1947

By W. M. Mobley

THE coal industry in Alabama, centered in Birmingham, has pioneered coal-beneficiation practice in the United States. The nature of the coal seams and mining methods employed have necessitated use of equipment and methods best adapted to the local conditions. Although all of the 30 or more coal seams now being mined in the state receive beneficiation, only the three most important producers of coking coals, the Pratt, Mary Lee and Black Creek, are discussed in detail. Nature of the seams, washability characteristics and equipment used are given as examples of the extent of work and progress in this field. The coal seams in Alabama are relatively thin and pitching, making mining difficult and expensive. Most of them are characterized by thin partings of rock or shale in the seam itself, as well as laminations of bone and rash. Mechanical mining methods have increased the occlusions from roof and floor to such an extent that nearly all the coal mined in the state must receive some treatment before it can be put on the market. During the year ending Sept. 30, 1943,1 18,129,792 tons of coal were mined in the state and 14,364,177 tons, or 79.2 per cent, received treatment. Excluding from the total the 1,223,014 tons produced by small wagon mines and the hand-picked lump coal, the amount receiving beneficiation would be more than 90.00 per cent. This is, by far, greater than in any other coal-producing state. The earliest record of coal beneficiation in Alabama was the installation in 1890 of an experimental Lung washer by Alexander Cunningham, for the Sloss Iron and Steel Co. at its blast furnace in Birmingham .2 In 1894 the Jeffrey Manufacturing Co. introduced the English Robinson washer, a combination of a hydraulic classifier and centrifugal machine. Erskine Ramsay, who has contributed so much to the coal industry, saw its possibilities as well as its mechanical defects and soon had his inventive mind at work. He added a sludge tank of his own design, and many Robinson-Ramsay washers were installed in Alabama and other states. The Stewart jig appeared in 1900, followed by the Montgomery jig in 1910 and both have found extensive use. Increased interest in this field led to new designs, such as the American, Elmore; Burke and Faust. The first Baum-type Norton jig was operated in 1930 and within the last five years six large installations of this type have been made by the McNally-Pittsburg, Jeffrey and Link-Belt Companies. Wet-washing tables were introduced in 1922 but not extensively used until recently. The two most popular types are the Deister-Overstrom and Deister Plat-O. The coal-cleaning equipment used in Alabama has been relatively simple, yet efficient, but as the amount of impurities in the raw coal has been increased by mechanical mining and labor costs have become higher, much interest has been shown in sand cones, froth flotation and

Jan 1, 1945

By W. M. Mobley

The coal industry in Alabama, centered in Birmingham, has pioneered coal-bene-ficiation practice in the United States. The nature of the coal seams and mining methods employed have necessitated use of equipment and methods best adapted to the local conditions. Although all of the 30 or more coal seams now being mined in the state receive beneficiation, only the three most important producers of coking coals, the Pratt, Mary Lee and Black Creek, are discussed in detail. Nature of the seams, washability characteristics and equipment used are given as examples of the extent of work and progress in this field. The coal seams in Alabama are relatively thin and pitching, making mining difficult and expensive. Most of them are characterized by thin partings of rock or shale in the seam itself, as well as laminations of bone and rash. Mechanical mining methods have increased the occlusions from roof and floor to such an extent that nearly all the coal mined in the state must receive some treatment before it can be put on the market. During the year ending Sept. 30, 1943,' 18,129,792 tons of coal were mined in the state and 14,364,177 tons, or 79.2 per cent, received treatment. Excluding from the total the 1,223,014 tons produced by small wagon mines and the hand-picked lump coal, the amount re- ceiving beneficiation would be more than 90.00 per cent. This is, by far, greater than in any other coal-producing state. The earliest record of coal beneficiation in Alabama was the installation in 1890 of an experimental Lurig washer by Alexander Cunningham, for the Sloss Iron and Steel Co. at its blast furnace in Birmingham.2 In 1894 the Jeffrey Manufacturing Co. introduced the English Robinson washer, a combination of a hydraulic classifier and centrifugal machine. Erskine Ramsay, who has contributed so much to the coal industry, saw its possibilities as well as its mechanical defects and soon had his inventive mind at work. He added a sludge tank of his own design, and many Robinson-Ramsay washers were installed in Alabama and other states. The Stewart jig appeared in 1900, followed by the Montgomery jig in 1910 and both have found extensive use. Increased interest in this field led to new designs, such as the American, Elmore, Burke and Faust. The first Baum-type Norton jig was operated in 1930 and within the last five years six large installations of this type have been made by the McNally-Pitts-burg, Jeffrey and Link-Belt Companies. Wet-washing tables were introduced in 1922 but not extensively used until recently. The two most popular types are the Deister-Overstrom and Deister Plat-O. The coal-cleaning equipment used in Alabama has been relatively simple, yet efficient, but as the amount of impurities in the raw coal has been increased by mechanical mining and labor costs have become higher, much interest has been shown in sand cones, froth flotation and

Jan 1, 1947

By Oliver Bowles

Slate is a fine-grained rock that has a more or less perfect natural cleavage, permitting it to be split readily into thin, smooth sheets. According to a definition established by the American Society for Testing Materials, slate is "a microgranular crystalline rock derived from argillaceous sediments by regional metamorphism and characterized by a perfect cleavage entirely independent of original bedding, which cleavage has been induced by pressure within the earth." Origin and Character Slates have originated from sedimentary deposits consisting largely of clay. Such materials were carried by streams and deposited in seas or lakes in successive horizontal beds. Other materials such as calcium carbonate, sand, or gravel may have been deposited over the clays, and the pressure of these superimposed materials gradually consolidated the materials below into bedded deposits of shale. Shale is a stratified rock formed by recrystallization of the clay plus adsorbed potash into the mica, sericite. Shale has neither the strength nor the splitting properties of slate since the mica is fine and the flakes unoriented, and the quartz grains do not interlock. Many shales, however, have been subjected to intense metamorphism. Mountain-building forces ever at work in the earth's crust may crumple, squeeze, and fold the shales. At the same time, accompanying high pressures and temperatures changed the original minerals into mica, interlocking quartz, or chlorite. Both mica and chlorite consist of minute tabular sheets or flakes with perfect cleavage. The intense pressure and movement tend to orient these flakes in parallel positions normal to the direction of pressure. The parallelism of the flakes results in the tendency to split with ease in one direction, which has been termed "slaty cleavage," and which is the outstanding characteristic of slate. Actually, the cleavage is through the cleavages of the individual micaceous plates. The original bedding of the slate is often folded and contorted, and the slaty cleavage commonly cuts across it at sharp angles. Composition MINERALOGICAL COMPOSITION The most abundant mineral in most slates is white mica (sericite), a hydrous silicate of potash and aluminum. It is present in very small flakes recognizable only with a microscope. Small grains of quartz (silicon dioxide) are also abundant and are regularly distributed among the mica flakes. The mica-like mineral, chlorite, is usually present in considerable quantities. Chlorites are of several kinds, the more common being hydrous silicates of aluminum and iron or magnesium. Other common minerals present in small quantities are rutile, clay, hematite, pyrite, carbonaceous matter, feldspar, zircon, tourmaline, calcite, dolomite, and siderite. The general range of the chief constituents is about as follows: Sericite, 38 to 40; quartz, 31 to 45; chlorite, 6 to 18; hematite, 3 to 6; and rutile, 1 to 1 ½ pct. CHEMICAL COMPOSITION Results of many analyses indicate that clays, shales, and slates differ little in chemical composition. The changes that take place during metamorphism are confined largely to rearrangement of the elements into new minerals with accompanying changes in physical properties such as hardness and cleavage. The general

Jan 1, 1960

By W. M. Mobley

The coal industry in Alabama, centered in Birmingham, has pioneered coal-bene-ficiation practice in the United States. The nature of the coal seams and mining methods employed have necessitated use of equipment and methods best adapted to the local conditions. Although all of the 30 or more coal seams now being mined in the state receive beneficiation, only the three most important producers of coking coals, the Pratt, Mary Lee and Black Creek, are discussed in detail. Nature of the seams, washability characteristics and equipment used are given as examples of the extent of work and progress in this field. The coal seams in Alabama are relatively thin and pitching, making mining difficult and expensive. Most of them are characterized by thin partings of rock or shale in the seam itself, as well as laminations of bone and rash. Mechanical mining methods have increased the occlusions from roof and floor to such an extent that nearly all the coal mined in the state must receive some treatment before it can be put on the market. During the year ending Sept. 30, 1943,1 18,129,792 tons of coal were mined in the state and 14,364,177 tons, or 79.2 per cent, received treatment. Excluding from the total the 1,223,014 tons produced by small wagon mines and the hand-picked lump coal, the amount re- ceiving beneficiation would be more than 90.00 per cent. This is, by far, greater than in any other coal-producing state. The earliest record of coal beneficiation in Alabama was the installation in 1890 of an experimental rig washer by Alexander Cunningham, for the Sloss Iron and Steel Co. at its blast furnace in Birmingham.* In 1894 the Jeffrey Manufacturing Co. introduced the English Robinson washer, a combination of a hydraulic classifier and centrifugal machine. Erskine Ramsay, who has contributed so much to the coal industry, saw its possibilities as well as its mechanical defects and soon had his inventive mind at work. He added a sludge tank of his own design, and many Robinson-Ramsay washers were installed in Alabama and other states. The Stewart jig appeared in 1900, followed by the Montgomery jig in 1910 and both have found extensive use. Increased interest in this field led to new designs, such as the American, Elmore, Burke and Faust. The first Baum-type Norton jig was operated in 1930 and within the last five years six large installations of this type have been made by the McNally-Pitts-burg, Jeffrey and Link-Belt Companies. Wet-washing tables were introduced in 1922 but not extensively used until recently. The two most popular types are the Deister-Overstrom and Deister Plat-O. The coal-cleaning equipment used in Alabama has been relatively simple, yet efficient, but as the amount of impurities in the raw coal has been increased by mechanical mining and labor costs have become higher, much interest has been shown in sand cones, froth flotation and

Jan 1, 1947

By John Birkinbine

Awakened public interest in efforts to conserve natural resources will certainly be appreciated by the members of the American Institute of Mining Engineers, and a discussion upon conservation may well form a part of one of the Institute meetings, for the records of papers and discussions which appear in the 38 volumes of its Transactions are replete with evidence of efforts in this direction. Every process which reduces the fuel consumed or the power applied per unit of product; every utilization of waste material, or employment of that formerly rejected, to obtain something of value; every feature of construction or operation which lessens the labor required or increases the output per employee, is an advance in the direction of true conservation. This may not appear from the records of late conferences or from published articles, in which the effort seems to be concen-

Jan 1, 1910

By J. F. Wolff, Anson A. Betts

The following correspondence relating to a paper bearing the above title, presented by J. F. Wolff, at the New York meeting in February, 1917, and published in the Transactions, Volume LVI, page 142, has passed between the author of the paper, and Mr. Anson G. Betts, and is interesting, although it was received much too late for incorporation in its proper place in Volume LVI. Anson G. Betts, Asheville, N. C.—1. I should like to ask Mr. Wolff if he finds from analysis of the iron formation and of the iron ore, and from the relative amounts of each in each unit area of the formation, unleached and after leaching, that the iron remains entirely insoluble and the total quantity still remains present; or whether he finds that some of the iron is removed, or possibly even added by deposition from the water passing through the formation. 2. The water that passed into the iron formation had to go somewhere; was it absorbed by underlying formations through hydration, or, after passing through the ore formation, did it come to the surface in springs at a lower elevation, or how did it escape from the ground? 3. I should like to ask Mr. Wolff whether he finds that the iron formation in the sedimentary series does not come next to the quartzites and generally between the quartzites and slates. J. I?. Wolff, Duluth, Minn.—1. In common with others, you appear to have some hesitancy in accepting the fact of the removal, by solution, of the enormous quantity of silica which has been leached out of portions of the Biwabik iron formation, thus forming orebodies of merchantable iron ore. I believe that even Dr. Waldemar Lindgren once hesitated to accept this fact. However, the evidence is so simple and absolutely conclusive that the fact is established beyond all question. At the contact of orebodies with their rock walls, the bands of iron ore in the orebody can be seen in contact with the corresponding bands of original iron oxide in the rock wall, and the chert layers in the rock wall can be seen to give place to fine granular material (fine silica and iron oxide) and pore space. This is especially noticeable where slumping at the rock walls has not been so great as to displace the layers in the orebody from their contact with their corresponding layers in the rock wall. Although complete analyses of the entire original rocks in the iron series have not been made in any place, to my knowledge, from the best data at hand as to the average analysis of the Biwabik series and the

Jan 1, 1920

By George L. Adams

There is an extensive literature relative to gas, oil, and the more solid hydrocarbons; but when it has all been digested and summarized, the resulting information is far from being satisfactory. The problems which have received the most attention are naturally those which relate to the successful exploitation and utilization of the deposits. From what is known of their geologic occurrence, theories have been formulated and rules laid down for the guidance of prospectors. The technology of the products has been made the subject of special chemical investigations. The geologic interrelation of the hydrocarbons, however, has not been considered in a broad manner, and the principles which have governed the origin of the economic bodies have been but imperfectly expressed. On the other hand, metalliferous deposits have been widely

Jan 1, 1903

For the first time in the history of shaft sinking, the concept of mid-shaft loading has been used. By making use of available hoisting capacity during drilling periods, development work on underground hoist chambers and ore-pass and ventilation by-pass systems at Vaal Reefs South gold mine is being done simultaneously with sinking. This factor, together with the unusual configuration and design of the twin-shaft system at Vaal Reefs South, and the use of raise borers in the installation of ore-pass and ventilation by-pass systems, will mean that the shaft will be commissioned at least a year earlier than would have been possible had conventional methods been used. The possibilities of mid-shaft loading in reducing the time normally taken by shaft service development were recognized by Anglo American Corp. consulting engineers and Shaft Sinkers Pty. Ltd., the company which is sinking both shafts at Vaal Reefs.

Jan 1, 1970

By John S. Alexander

DURING the past few years the block coal of Indiana has been talked about and written upon to such an extent, that almost every one at all interested in such subjects, has been made acquainted with the area and geographical position of the field, the quality and peculiar properties of the coal, the thickness of the veins, the manner of mining, etc. The writer, therefore, taking for granted that, to those present all this is familiar ground, desires more especially to call attention to the position this coal takes in the market, and at those points of consumption where it is brought in direct competition with rival fuels. Chicago, thus far, has been the chief consumer of Indiana block coal, the distance from the mines at Brazil, via Terre Haute and the

By Andre Hubaux

In the writer's opinion, more stress should be put on field and microscope observations, as J. L. Gillson does. His discovery of relics of big labradorite feldspars from the Marcy anorthosite in all the other rocks is proof enough that previous field observations have been inadequate. The writer's field experience with anorthositic massifs is limited to the Egersund-Sogndal district in southern Norway; however, this is a very large and well exposed area. It seems to have so many points in common with the Adirondack region that a detailed comparison should be beneficial. This comparison was not possible 20 years ago, owing to the scarcity of geological data, at least for Norway. Both regions are now far better known-the Norway district because of the work of Professors Bugge and Barth33-35 and especially because of the extensive field and microscopic research of P. Michot,36-46 who introduced me in the field to the problems of that region.

Jan 3, 1958