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By R. C. Mahon

During the early history of the Lake Superior district, tamarack timber was used almost exclusively in the wines. It had the strength and lasting qualities necessary for a satisfactory mining timber. But about fifteen years ago the tamarack trees were attacked by a blight which killed nearly all of them so today no tamarack timber is available. Hemlock, spruce, and poplar have neither the necessary strength nor the lasting qualities for mining timber, but a large supply of maple and birch is available. These have ample strength but, when placed underground, fail by decay in about three years. This means that, instead of replacing the timber sets once in fifteen years, it must be done five or more times in the same space of time which involves not only incraesed timber costs but more important, an increased labor cost.

Jan 1, 1949

By R. C. Mahon

Operators concerned with the destruction of their piping by acid mine waters will be interested in the method by which this problem was solved at the Cardiff mine of the Homer group. Rubber lined, or acid resisting metal pipes were found too expensive. Casting concrete lining in pipe would have required a minimum thickness of one inch, thus excessively reducing the pipe's diameter, as well as taking twenty four hours per length of pipe. The Naylor Pipe Co. of Chicago, having experimented with centrifugal lining of pipe with concrete, provided information which eventually solved the problem. An experimental plant was constructed as shown, and the following procedure developed : (1) Kerosene is used to remove the interior oil coating of new pipe. Closed with blank flanges, the pipe is revolved for eight minutes at varying speeds. Stopping and starting the motor achieves a good washing action. The kerosene is then drained off, and similar washing action with caustic soda removes any excess. Swabbing in done with burlap fastened to a 1/2-in. pipe. (2) The aggregate, made of one. part quick-setting cement and two

Jan 1, 1949

By JAMES J. PURDY

The great majority of stokers used in residential heating installations are of the clinkering type. Because of inherent characteristics of the under- feed combustion process as it occurs in these small stokers, and because of the wide range of operating conditions encountered in residential heating schedules, not all bituminous coals can be used successfully in residential underfeed units. The problem of providing consumer satisfaction has been attacked by the joint efforts of the stoker manufacturers and the coal industry; the stoker manufacturers have been concerned with improving their product to permit the use of a wider range of coals, and coal operators have made every effort to market selected and better prepared coals. In view of the wide range of physical characteristics and chemical properties of bituminous coals, the problems are real and are receiving increased attention.

Jan 1, 1949

By John V. Beall

During the last quarter of 1948, two new machines, which may revolutionize the coal mining industry, made their first public appearance within two months of each other. Both are designed to mine and load coal continuously. On Oct. 27, the "Colmol," invented by C. H. Snyder and A. E. Lamm, president and executive vice-president, respectively, of the Sunnyhill Coal Co., was demonstrated at the No. 8 mine of that Company at New Lexington, Ohio. The "Joy Continuous Miner," invented by H. F. Silver, president of the Silver Engineering Works, Denver, and developed and manufactured by the Joy Manufacturing Co., was demonstrated at the Mathies mine, near Finleyville, Pa., in the Pittsburgh coal seam.

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By W. M. Myers

THE hydraulic properties exhibited by the calcination products of certain limestones were recognized at an early datemore than 2000 years ago. It was known that calcined limestone with the addition of other minerals would react with water and produce an insoluble and stable product. This material could be cast in desired forms or could be used as a cement for the unification of other materials in large masses or for bonding brick or masonry structures. Cements are essentially mineral glues and it is their ability to unify other materials plus their fluidity when first mixed with water, enabling the mass to assume any desired shape, that has made them so extraordinarily useful to modern industry. Like other glues, cements do not exhibit their maximum strength when used alone and only when mixed with proper aggregates do their optimum properties appear. The resulting concrete, a mixture of cement, mineral aggregates and frequently of reinforcing steel, exhibits the most desirable properties of the individual constituents with regard to tensile strength, stability and permanence. The speed with which such mixtures can be -prepared and installed in place with mechanical equipment has facilitated their adoption by the engineering profession concerned with the construction industries. The development and application of improved methods of manufacture have resulted in such economies that the finished product can be sold at a remarkably low price. In addition, the necessary raw materials are of such common occurrence and wide geographic distribution that the manufacture of cement was established in 34 of the 48 states by 1946. Plants under construction will add to this number. In recent years the industry has been characterized by the development of a number of new cements designed to possess special properties essential for use in unusual environments. These have introduced the use of some new raw materials and also have complicated the processes of manufacture. In the following pages, the major varieties of cement of commercial importance are treated in the chronological order of their appearance on the market.

Jan 1, 1949

FOREWORD5 INTRODUCTION 7 ACKNOWLEDGMENTS II BERGBÜCHLEIN TRANSLATION OF THE TEXT 17 HISTORY AND BIBLIOGRAPHY OF THE Berghüchlein 49 NOTES ON TRANSLATION AND ACKNOWLEDGMENTS 63 THREE ILLUSTRATIONS FROM THE EARLIER UNDATED EDITION 65 [ ]

Jan 1, 1949

By G. F. Jenkins

ASBESTOS is a general term embracing the fibrous varieties of a number of minerals. Of these, the hydrous magnesium silicate, chrysotile (H4Mg3Si209), a variety of serpentine, is the most abundant and useful to industry. All other types of asbestos belong to the amphibole group of minerals and are classified as: crocidolite, NaFe(SiO3), FeSiO3; anthophyllite, (MgFe)SiO3; amosite, also a ferromagnesium silicate but with iron content higher than that of anthophyllite; tremolite, CaMg3(SiO3)4; and, actinolite, Ca (MgFe)3(SiO3)4. PROPERTIES The commercial value of asbestos depends largely on the physical property that permits it to be readily separated into fine filaments of high tensile strength and flexibility, which, coupled with the fact that it has the quality of incombustibility of a mineral-in distinction to vegetable and animal fibers-makes it of unique usefulness for many purposes. To some extent, the value depends upon the length of the fiber, although extreme length is neither necessary nor desirable for most purposes. Chrysotile occurs as cross-fiber veins, in which the asbestos fibers are approximately' at right angles to the vein walls, with vein width- or fiber length-seldom exceeding 2 or 3 in.; also as slip-fiber, in which the fibers 'lie in the same plane as the vein or on slippage planes. A cleanly broken vein of cross-fiber has a pearly luster and may range from a deep green or brown color to light shades of yellowish green or cream. When of good quality, the fiber filaments forming the vein may be easily drawn away from their neighbors and exhibit a fine silkiness and pure white color. They may be twisted into a thread and when flexed between thumb and fingers are found to be strong and pliable. Chrysotile withstands comparatively high temperatures without breaking down completely or fusing but begins to lose water of crystalliza-

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Jan 1, 1949

By A. T. Goldbeck

THE use of stone as a building material in relatively large blocks is recorded in ancient historical records but only within the past 200 years has broken stone in small sizes begun to have extensive use, principally in highway construction. Tresaguet, in 1764, describing his method for highway construction in France, required the top surface to be built of stone about the size of a walnut, broken by the use of a hammer. It is said that the Romans, in the top layer of their rather massive roads, used large stones bonded together with lime mortar and bedded in small stones mixed with mortar. Much of the early macadam as built by McAdam around 1815 in England was made with hand-sledged broken stone. In 1858, the use of crushed or broken stone received a great impetus from the invention in that year by Eli Whitney Blake of what is said to be the world's first stone crusher. As a consequence of that invention, stone could be crushed to small sizes with considerable ease and, as a natural result, the use of crushed stone in macadam roads and as railroad ballast increased at a great rate. Also, as portland cement came into use, machine-produced crushed stone furnished readily available aggregate. Rapidly, other uses developed, such as for fluxstone in the production of pig iron and for other metallurgical operations and chemical utilizations. These utilizations made for the rapid growth of the crushed-stone industry and this growth is still proceeding with the growth of population and the development of new uses, notably the employment of limestone for the improvement of soils for agricultural purposes. The industries of which the production of crushed stone is a part have a tonnage second only to that of mineral fuel in the mineral industries of this country.

Jan 1, 1949

By NA NA

Jan 1, 1949

By Oliver Bowles

DIMENSION stone is a convenient term applied to stone sold in blocks or slabs of specified shapes and usually of specified sizes, as contrasted with crushed, broken and pulverized stone, discussed in another chapter. Dimension stone includes cut stone, rough building stone, ashlar, rubble, paving blocks, curbing and flagging. Riprap-large, irregular blocks used for shore protection-is classed more properly with crushed and broken stone. COMPOSITION, VARIETIES AND PROPERTIES Stones used as blocks or slabs are of many kinds. The principal varieties are granite, sandstone, limestone and marble. Slate is covered in another chapter. Granite is a visibly granular crystalline rock consisting essentially of feldspar, quartz, and mica or hornblende. Limestone consists essentially of calcium carbonate, with which may be associated certain impurities such as clay, sand, or iron oxide. Dolomites and magnesium limestones used as dimension stone are classed with the high- calcium limestones, as they are used in the same way. Marble is a crystalline form of limestone. Sandstone consists essentially of silica in the form of sand grains cemented together into a coherent mass. Although rock occurrences are numerous and widespread, the ex- acting requirements of use condemn all but a small fraction of them for commercial use as dimension stone. No deposit that has closely spaced cracks, lines of weakness, or joints can be so used because sound blocks of moderate to large size are demanded. Uniform texture and grain size, constant and attractive color, and freedom from impurities that may cause stains or deterioration usually are required also. Hardness is a variable property. Granites are as hard as or harder than steel while limestones and marbles may be scratched easily with a knife. The hardness of a sandstone depends upon the degree of cementation of the grains. Workability depends to a considerable extent on hardness, but the degree of hardness has little influence on use except when stones are subjected to severe abrasion, as on steps or floors. "Texture" as applied to stone relates to the arrangement, uniformity, and size of the constituent grains.

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