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Jan 1, 1924

Discussion of the paper of Earl S. Bardwell, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 79, July, 1913, pp. .1429 to 1441. H. O. HOFMAN, Boston, Mass. (communication to the Secretary*) :-It is pleasing to the originators of the planimetric determination of oxygen in refined copper to see that the method has been taken up by a large smelting plant to be used in every-day work after it has been simplified to suit the new conditions. Several years ago Huntington and Desch 1 had improved our mode of working. They projected the developed negative on to a screen, traced the outlines of the picture with a pencil, drew a border, and measured one constituent with. the planimeter. In order to give the work greater precision, they divided the area into squares of 1 cm. side, shaded the

Jan 11, 1913

By Duane N. Goens, Clifford R. Porter

A 91 kg/h (200 lb per hr) pilot plant was constructed according to "Magnex" design. A non-compliance eastern coal which would generate more than 0.85 kg of SO2 per GJ (2.0 lb of SO2 per million Btu) upon burning was brought into compliance less than 0.52 kg of SO2 per GJ (1.2 lb SO2 per million Btu) during continuous operation of the pilot plant. Approximately 85% of the pyritic sulfur was removed while recovering 90% of the Btu of the feed coal. Pilot plant operation is summarized and preliminary economics presented. Present status of the Magnex design program is reviewed.

Jan 1, 1980

Ore deposits of commercial grade are local concentrations of great rarity when considered in relation to the area of unmineralized land surfaces, and they must therefore be considered as the products of exceptional and complex conditions. The data collected from a great number of individual deposits are sufficient to permit certain broad generalizations in regard to the conditions favorable to ore deposition which even numerous exceptions do not invalidate. The broadest general relation of ore deposits is with intrusive rocks, and while there are notable exceptions, the great majority of ore deposits have a visible or closely inferred connection with intrusive rock masses. Conditions that permit the dissipation of the ore-bearing vehicles do not permit the concentration of metals in deposits; the prime factor to consider in this connection is that structural conditions must be such as tend to concentrate and not to dissipate the ore-bearing solutions. The disadvantage of extrusive rocks is at once apparent; any metals the magma may have contained are dissipated at the surface and are lost; with the exception of tiny vugs and cracks in quickly cooled flows, no concentrations of metals are known in extrusive rocks, and the lack of confinement and quick cooling apparently do not permit extrusives to exert mineralizing effect upon the rocks with which they come in contact. The close mineralogical similarity between extrusives and intrusives, and the great difference in mineralizing power is a proof of the ease with which magmas part with their metallic content, and of the mobility of the ore-bearing vehicles in comparison with the parent magma.

Jan 1, 1932

By R. Simon

Maurer's review1 summarizes quite thoroughly the various theoretical developments and experimental findings that contribute to the knowledge of rock mechanics in drilling. This discussion supplements Maurer's paper by including generalities that either have been incompletely treated in his review, or formulated from new considerations by the discussant and from hitherto unpublished experimental data. These generalities are associated with the observation that all mechanical methods of rock drilling essentially comprise a sequence of indexed, concentrated loadings on the bottom of the hole being drilled. A concentrated loading is defined as a mechanical loading by a tool that contacts at any one time only a small fraction of the surface of the body being worked and penetrates only a small fraction of the body thickness. The surface in this application is the bottom of the hole. The deformation of ductile material by concentrated loading has received considerable attention because of the importance of indentation tests for measuring hardness of metals. Some of the generalities involved in concentrated loadings on ductile materials apply also to concentrated loadings on more brittle materials such as rock. Among these generalities is the applicability of similitude considerations to scaling laws and to force-displacement and energy-volume characteristics for tools of various shapes, as summarized by Tabor.2 Vork on the flow and fracture behaviors of glass loaded with pyramidal and spherical indenters is reviewed by Douglas.3 Maurer refers to the work of Evans and Murrell on wedge loadings on coal and on mixtures of pitch and sand. It is evident from Maurer's paper that a considerable portion of the studies of rock mechanics in drilling, such as crater formation experiments, has involved concentrated loadings on rock.

Jan 1, 1967

By John Hall

THE Fremont test for measuring the energy consumed in breaking a notched bar of steel is not so well known in this country as it deserves to be. The test specimen used in this test is about 3/8 by 1/4 by about 1 1/4 in., notched with a hack saw on the lower side to cause the piece to break at a fixed point. A weight of 10 kg. falling 4 m., and provided with a knife or chisel which strikes the specimen, breaks the test piece by impact. The residual force in the falling weight after it has broken the specimen is recorded by a suitable device, and the difference between the total energy and the residual energy of the weight (in kilogrammeters) is the force consumed in breaking the specimen. An experience of several years with the Fremont testing machine has shown its great value in readily detecting brittleness not revealed by tensile testing or slow bending testing. I this paper it is proposed to discuss (1) the supersensitiveness of the test as applied to cast steel and (2) its value in revealing the effect of heat treatment under certain conditions. .

Jan 7, 1913

By H. Ries

THE stabilization of a gravel road with soil is a method of treatment developed in recent years by the United States Bureau of Public Roads for the purpose of binding the constituents together better, and maintain-ing a more durable surface. The process consists in adding to the gravel or crushed stone and sand, a soil mortar, so-called, of fine sand, silt and clay, mixed in the proper proportions. The coarse gravel and sand supply structural strength and hardness; the fine sand adds embedment support to the coarse sand; the silt acts as a filler to prevent the granular particles from rocking; while the clay serves not only as a binder but also provides pores minute enough to cause connecting moisture films which are supposed to have high cohesive properties1. It will be recognized that the clay is an important ingredient both when wet and dry, and should not show excessive expansion when wet, nor correspondingly high shrinkage in drying, as otherwise there is danger of unseating the nonplastic particles. Such a stabilized road, although an improvement on one with a floating surface, will in course of time be subject to wear, and become dusty when the clay dries out and breaks up. It has been found that if some salts are added to the road mixture they tend to maintain the soil moisture and prevent dustiness of the road or raveling of the road surface. In addition to this, it is claimed that these dissolved salts cause a thinning of the moisture films on the particles, thus permitting greater compaction of the road mixture, and thereby increasing its density. This fact can be proved by noting the increased compaction which a road mixture shows when certain salts are added to the soil water. Since certain chemical substances such as sodium chloride are electro-lytes, the question arises whether they cannot have some effect on. the qualities of the clay in the soil mortar, and perhaps improve them. In view of the fact that certain salts seem to exert a favorable effect on the road mixture it is desirable that they be held in the road soil as long a time as possible.

Jan 1, 1936

By W. O. Brown

A laboratory investigation was conducted to determine quantitatively the extent to which connate water was contacted and displaced by invading flood water. In these experiments the connate water in unconsoli-dated sand packed columns was completely displaced by injecting water. The nature of this displacement was similar to that previously described for single-phase miscible fluid displacement studies, and thus the presence of a non-wetting immiscible phase did not appreciably change the nature of the displacement. The effects of water injection rate, column length, and oil viscosity on connate water displacement were investi-gated. It is concluded that the connate water in a reservoir is the water which actually displaces oil from the pores of the rock during a water flood. During a water flood the connate water forms a zone which separates the invading flood water from the continuous oil phase. The size and shape of connate water bank is chiefly dependent oil the oil viscosity and the column length. INTRODUCTION Water flooding is one of the most widely used techniques for the secondary recovery of oil. Presently, however, it is still not possible to recover all the oil in a reservoir by water flooding. The research described in this paper was conducted as part of a study to determine the conditions under which 100 per cent oil recovery could be attained by water flooding. The particular objective of this work was to determine if any chemical agent, regardless of its nature, placed in the flood water could be effective in influencing the mechanism of displacement of the oil by water. It has been known for many years that water does not displace all the oil in a reservoir because a portion of the oil is "trapped" and held immobile by capillary forces. This oil is trapped within the pores of a water-wet rock when it becomes broken into discontinuous globules. Initially, when oil is present at high saturations within the pores of a water-wet rock, the connate water forms rings around the points of contact of the sand grains and may even completely fill small cavities between grains, whereas the oil occupies the larger void spaces between the grains.' Under these conditions, the oil in these spaces is in the form of irregular but continuous filaments, the diameters of which depend on the geometry of the sand pores. The filaments are formed by the oil contained in the small cells which are formed between the sand grains and are connected to their neighboring cells by channels or tunnels formed by pendular rings of water. At a high oil saturation, the oil filaments conform approximately to the shape and size of the cells and their connecting tunnels. Starting with this distribution, as the water saturation is increased the water layers in the small cavities and on the surface of the grains grow. As this occurs, the water rings grow and the diameters of the oil filaments decrease. When an oil filament is reduced to a critically small diameter, the filament breaks, and its tunnel fills completely with water. Any oil which remains within a cell after all its connecting tunnels have been water-filled is trapped as a discontinuous globule. Once the oil has become trapped, the capillary forces oppose distortion of the globules and may prevent their being squeezed through the water-filled tunnels. Only a very small pressure gradient is sufficient to keep oil moving as a continuous filament. On the other hand, once the filament has broken into discontinuous oil droplets a relatively large force is required to distort the surface of a drop and move it through a water-

Jan 1, 1958

By F. M. Sandoval, R. E. Ries, J. F. Power

Returning the original soil material to the surface of smoothed mine spoils is a practical means of restoring agricultural productivity. Research has established that high-sodium spoils in North Dakota: (1) must be covered with about 70 cm of soil material to achieve maximum production; (2) top-soil must be segregated and spread separately from subsoil; (3) potential production depends on the quality of the soil material returned; and (4) erosion and upward salt movement must be controlled for sustained production. Erosion is best controlled by reducing final grades as much as possible during the smoothing process followed by prompt establishment of vegetation.

Jan 1, 1980

By A. Boltax

Precipitation processes occurring during both furnace cooling and aging of copper-iron albys were studied by means of electrical and magnetic measurements. On furnace cooling, two distinct stages in the precipitation process were detected; one occurring above and the other below 850° C. The kinetics of precipitation from quenched alloys were studied between 200° and 700°C. The reaction appears to be consistent with the concept of tmcleation of precipitate particles at dislocation loops formed by the clustering of quenched-in vacancies. A study Of in copper-iron alloys is particularly interesting because the combination of magnetic and electrical properties in these allovs provides a quantitative means of following the course of the precipitation reaction. (The details of precip-

Jan 1, 1961

By V. H. Wilhelm

In contrast with the previous year's activity, the California oil industry for 1938 showed a decrease in drilling, market demand, and discovery of new oil reserves, although there was an increase in oil production. Although additions to reserves from new fields and extensions were less than withdrawals during the year, reappraisals of discoveries in 1937 added to new discoreries during 1938 amounted to over 300,000,000 bbl. The following comparative statement shows the important changes in various phases of the industry: Throughout the year the storage situation became progressively more acute, owing principally to less Pacific foreign demand, and increased potential from drilling the newly discovered fields and pools (Fig. 1). California storage increased approximately 32,000,000 bbl. during 1938, most of which (approximately 18,000,000 bbl.) was heavy crude and residuum. The market demand for the year was around 600,000 bbl. per day. Because of the trend toward Diesel power for heavy transportation, the non-gasoline-bearing crudes arc fast becoming a drug on the market. New discoveries were instrumental in increasing the potential production of the state from 1,076,000 bbl. per day in January to an all-time high of 1,420,000 bbl. per day at the close of the year; although the indicated reserves of these new discoveries were not equal to the yearly withdrawal of 249,000,000 bbl. As of the end of 1938, the state was voluntarily curtailed about 58 per cent. As a result of prospecting during the year, six new fields were discovered, three fields were extended, and deeper zones were reached in five of the older fields.

Jan 1, 1939

By V. H. Wilhelm

In contrast with the previous year's activity, the California oil industry for 1938 showed a decrease in drilling, market demand, and discovery of new oil reserves, although there was an increase in oil production. Although additions to reserves from new fields and extensions were less than withdrawals during the year, reappraisals of discoveries in 1937 added to new discoreries during 1938 amounted to over 300,000,000 bbl. The following comparative statement shows the important changes in various phases of the industry: Throughout the year the storage situation became progressively more acute, owing principally to less Pacific foreign demand, and increased potential from drilling the newly discovered fields and pools (Fig. 1). California storage increased approximately 32,000,000 bbl. during 1938, most of which (approximately 18,000,000 bbl.) was heavy crude and residuum. The market demand for the year was around 600,000 bbl. per day. Because of the trend toward Diesel power for heavy transportation, the non-gasoline-bearing crudes arc fast becoming a drug on the market. New discoveries were instrumental in increasing the potential production of the state from 1,076,000 bbl. per day in January to an all-time high of 1,420,000 bbl. per day at the close of the year; although the indicated reserves of these new discoveries were not equal to the yearly withdrawal of 249,000,000 bbl. As of the end of 1938, the state was voluntarily curtailed about 58 per cent. As a result of prospecting during the year, six new fields were discovered, three fields were extended, and deeper zones were reached in five of the older fields.

Jan 1, 1939

By Howard N. Eavenson

FROM the Pittsburgh coal bed in the four states of Pennsylvania, Ohio, Maryland and West Virginia has been produced an output that, at mine prices, represents a greater value than any other single mineral deposit in the world has yielded.12 While this distinction may in a few years pass to the gold reef of the Witwatersrand, it is possible that eventually, owing to the tremendous reserves still remaining, the ultimate yield of the Pittsburgh bed will be greater than that of any other known single deposit. Considering its importance, not a great deal has been written of its early history and development as a whole; most of the accounts have been of limited localities, or, at the most, of the area within a single state. In "Coal through the Ages" the writer mentioned some references to its early history, but this study will deal not only with its history but with the character of the bed, where and why it was first developed, and its effect upon the states in which it is found. It has not been the intention to write a detailed history of the development of the seam in each locality, as neither time nor inclination were available for doing such work, but only to show the influences that tended to hasten or retard such development. In general the historical matter ends about 1830, when geological surveys began to be made. Some of the maps show data available only since that time, and the sections about coal preparation and coking have been extended to the present time to show the changing conditions. It is believed that the early history includes all published records, and many more sources than those shown in the bibliography were consulted. It is quite likely that some references to coal in this area may be found in the unpublished papers of some of our early soldiers and colonizers, which exist in several libraries, and it is hoped that some future

Jan 1, 1938

By Frank C. Roberts

Neglecting the hydrogen and hydrocarbons, 1 will assume the following analysis as a fair average composition, by weight, of the waste gases escaping from a coke-burning blast-furnace: CO2............17.25 CO,............25.25 N,.............57.50 100.00 The 25.25 CO requires for combustion 62.6 of air, or 11.398 of oxygen, necessitating the passage of 48.202 nitrogen into the products of combustion. The latter, therefore, have the following composition: CO2,,............ 56.9 N,............105.7 Tile total specific heats of these quantities of the respective gases are 12.31 and 25.79, giving for the combined product, 38.1 approximately. That is, the product of combustion will absorb 38.1

Jan 1, 1889

By S. K. Asunmaa, W. D. English, N. A. Tiner, W. A. Cannon

This paper discusses the reaction of metal surfaces with fluorine. Fluorination reactions result in the formation of metal fluoride films which are "passive" toward further reaction of the metal with fluorine. These films are very adherent, and do not easily detach from the substrate metal by mechanical flexing or thermal shock. Exposure of passive films to a humid atmosphere produces hydrated metal fluorides which cause secondary fluorination reactions upon reexpo-sure of the metal surface to fluorine. The surface films formed range from 10 to 30A in thickness and they pow at the expense of surface oxide films. The apparent film formation is completed rapidly in 15 to 30 min on stainless steel and nickel surfaces. On copper and on Monel surfaces, the film at first grows rapidly, then increases slowly over an extended period of time. Passive films are formed at all fluorine pressures in the range from 0.1 to 1.4 atm at room temperature. ALL metals react when exposed to fluorine. These reactions generally produce surface films which consist of metal fluorides. The rate of reaction is largely determined by the extent to which these films are protective. Although there is an extensive literature concerning reactions of oxygen with metals, there are very few investigations reported concerning fluorine-metal reactions. Brown, Crabtree, and ~uncan' investigated the kinetics of the reaction of gaseous fluorine with copper metal which had been freshly reduced in hydrogen. The reaction rate was independent of pressure over the range from 6 to 60 torr. A logarithmic rate law was obeyed in the temperature range from 25" to 300" ~. There was some deviation at higher temperatures which could have been the onset of a parabolic law. The calculated film thicknesses ranged from about two molecular layers, 10A, for 5 hr exposure at room temperature to thirty-five molecular layers for 5 hr exposure at 200" . The authors concluded that no single mechanism could explain all the observations. O7Donnell and spatkowski2 studied the reaction of fluorine with copper at 450°C at pressures from lo to 133 torr. The reaction was found to be pressure -dependent and followed a logarithmic rate law. It was not entirely diffusion-controlled, and fluorine was thought to be the migrating species in the reaction. Miscellaneous metal-fluorine reactions were investigated by Haendler et ~1.~ Reaction products were identified but no rate data were determined. Air Prod- ucts and Chemicals, Inc., have conducted an investigation of reactions between fluorine and various metal powders at room temperature and 85° C. Fluoride film thickness as a function of time of exposure was reported on the assumption that the reaction takes place between fluorine and metal to form the normal metal fluoride. Surface areas of the powders were only estimated so the relative film thicknesses may not be exact. The data showed reaction rates which were generally logarithmic in character, the rate of film growth virtually ceasing after a few hours exposure time for some alloy powders. The effect of moisture on fluoride films was also investigated by measuring additional reaction with fluorine after exposure of passivated powders to atmosperic moisture. The fluorination of iron was studied by 0'~onnell~ at temperatures from 225" to 525" ~ and at pressures ranging from 20 to 200 torr. In all ranges, the reaction followed a logarithmic rate law and was dependent on the square root of the gas pressure. The author concluded that fluorine gas passes through pores in the film. As the film grows, the blocking of pores leads to a rapid decrease in reaction rate; hence a logarithmic rate law is observed. Jarry, Fischer, and Gunther' investigated the mechanism of the reaction of fluorine with nickel at about 600" to 700°C. On the basis of the metallographic examination of fluoride scales growing on the nickel and from separate radioautographic data, it was claimed that fluorine is the migrating species in the reaction. This is in sharp contrast to the growth of oxide films on nickel where it has been shown that nickel ions migrate through the scale to the gas-solid interface to react with oxygen. Few investigations have been reported of the reaction of fluorine with metal oxides. Such investigations should be of great significance for a better understanding of passivation in view of the ubiquitous oxide films on technical alloys. Haendler et al.3 studied the reaction of fluorine with oxides of copper, tin, titanium, zirconium, and vanadium. Copper (I) oxide reacted as follows in the temperature range 150" to 300"~: temperature above 300" ~ was required for the CuO to react to form additional copper fluoride. Ritter and smith7 also investigated the reaction of fluorine with copper (11) oxide. An oxide powder comprised of spherical particles with a fairly high surface area was reacted with fluorine, starting at room temperature and increasing to 100° C over a period of 3 or 4 hr. The initial reaction was slow until the fluoride film thickness reached about to or 15R at which time the reaction rate accelerated, then decreased again. Most of the kinetic data was obtained during this final phase of reaction. The authors conclude that the film grows slowly at first until the stresses developed in the distorted lattice are sufficient to rupture the initial

Jan 1, 1969

By S. H. Williston

IT is not often that bore hole surveys can be checked by actual civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bisbee, Ariz., drilled a 1245 ft, 8 in. diam, churn drill- hole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in- the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location. The noise of the drilling tools was reasonably clear, but the direction of sound was uncertain. Preliminary tests with available equipment were not successful in locating the bottom of the hole. Be- cause of the mineralized character of the area and the fact there was some casing in the hole, any magnetic method of well surveying would give results ' of doubtful value.

Jan 1, 1950

By N. Albon, J. F. Miller, R. W. Coutant

The deposition of nickel from nickel carbonyl onto amorphous substrates has been studied, with attention being paid to the specific effects of the physical and chemical nature of the substrate and to the effect of oxygen on the crystal morphology. With substrates having microscratches or etch lines, nu-cleation was observed to occur preferentially at these surface features. Flame polishing of the substrate surfaces was found to remove any regularity in preferred nucleation sites. Nucleation was observed to occur less readily on substrates having relatively low surface energies, e.g., Teflon and carbon, than on materials having relatively high surface energies such as fused silica. At low oxygen concentrations [Ni(CO)4/O2 > 54 x 1031, apparently pure and well-formed nickel crystals were observed to nucleate and grow irrespective of the presence of oxygen. At higher concentrations of oxygen, a secondary growth process, dependent upon oxygen concentration and resulting in a gradual change in crystal morphology, was observed. It is concluded that the influence of oxygen on the nucleation and growth of nickel is determined by the relative kinetics of the various possible reactions, and that under the experimental conditions employed the 0-Ni interaction occurs at some nucleation or prenuclea-tion stage. THE purpose of the research on crystal nucleation in chemical vapor deposition as described in this paper has been twofold: 1) to examine some effects arising from the use of amorphous substrates, and 2) to study the specific effects of oxygen on the nucleation and growth of nickel in a nickel carbonyl-carbon monoxide system. The nickel-nickel carbonyl system was chosen for study for several reasons: 1) nickel films are of potential interest in electronic technology, and 2) the deposition can be carried out at moderate temperatures, thus making possible detailed study of the processes occurring and the use of a variety of substrate materials (including some which melt at relatively low temperatures). Fairly well-characterized chemical kinetics and a broad background of information are available on the py-rolysis reactions and on the mechanisms of Ni-O interactions. NUCLEATION AND GROWTH THEORY The theoretical background for the analysis of nucleation and growth by vapor deposition for a one-component system (physical vapor deposition) and the problems encountered therein have been reviewed by Hirth and pound.' More recently Mande12 has indicated the difficulties of applying such theory to chemical systems. One of the major problems involved is the possible multiplicity of chemical reactions and deposition routes. For example, those reactions which are probably of significance in a discussion of the pyrolytic deposition of nickel from nickel carbonyl under the conditions of the present experimental work are illustrated in Fig. 1. As is true with most cases of chemical deposition, many of the quantitative data necessary for a complete analysis of the system are either not available or not directly measurable. However, with the present system, sufficient data are available for a discussion of nucleation and growth on a qualitative basis. Classically, the rate of nucleation of a monatomic species being deposited from a vapor phase is given by

Jan 1, 1965

By Prince Gelasio Caetani

PRESIDENT DWIGHT'S invitation to be a guest of the American Institute of Mining and Metal-lurgical Engineers was the first of the subsequently very numerous invitations to dinner I have received from my American friends. When I received his telegram I had not yet been even formally appointed Ambassador. I cannot tell you how deeply I appreciated it. It was a hearty welcome in returning to your country which has been for me a second home and it came from the American mining brotherhood which has been my second family.There are two distinct periods of learning in life. The first one are the years spent in school where we learn many things we after-wards forget; the second one are the years of prac-tical apprenticeship which engrave indelible signs in a man's character and shape his life. These latter years I spent in the United States and they have influenced the whole course of my life. I owe very much to my American friends who trained me. The earliest was Prof. Robert Peele, of Columbia University. At the Daly West mine, in Park City, Utah, he curbed my futuristic English spell-ing and had a hard time at it. Prof. James F. Kemp taught me that geology is a guess work just as unre-liable as the prediction of international events; he taught me also that a frank, honest and loyal character will lead a man equally straight through a mining report and through public life.

Jan 3, 1923

By James T. B. Ives

The map exhibited* as an example of my method of construct ing geological strata-maps is essentially an educational appliance. The method, however, is available for the production of maps of comparatively small areas, which, I am confident, will be found of great practical value to mining engineers. Before stating how the method may be so applied I will briefly describe the map exhibited, as the easiest way of making my meaning clear. Almost any region might be taken. This map represents the eastern half of the United States; and the geology is that of the map issued by the Geological Survey, and revised and extended subsequently by Professor Hitchcock for your Institute. I use ten cards, of the colors used in the geological map, each having the geog raphy of the area printed upon it; and I superimpose these in the order in which the colors occur in the index to the map. I next cut away a portion of each card, excepting the lowest, leaving only so much of each as represents the exposure of the formation of that color plus all those which overlie it. When that is done, the whole, looked at from a distance, appears to be an ordinary geological map. Looked at more closely, however, the formations are seen to overlie one another, as in nature. The cards are covered with glass in a frame, which, hinged at the bottom edge, can be let down. The cards are then found to be all hinged in the same manner, and they, too, may be lowered, one after the-other. I am told by teachers of geology of great experience and the highest reputation that by this appliance they will be assisted in im parting to students the first facts and principles of geological sci ence. Having let down the whole series of cards, until that repre senting the Archaean is seen underlying all the rest, the teacher will gradually rebuild it. The Cambrian will thus be laid down upon the Archaean before the eyes of the class, the Silurian upon that,

Jan 1, 1888

By F. Lynwood Garrison

It is not intended to make in the present paper any deduction or to formulate any theories from the results obtained by experiments. The further expenditure of considerable time and labor would be required to obtain a sufficient basis for positive assertions as to the microscopic structure of the different varieties of iron and steel, and the structural changes which take place in them. It is therefore my purpose at this time to offer simply a synopsis of the general results arrived at in a few months' work, a brief description of apparatus used, and a few hints as to the preparation and preservation of the material which it is intended to investigate. The study of the microscopic structure of iron and steel is not altogether new. Some attention has been given it in both England and Germany. But the foreign publications on the subject have thus far been confined, so far as I am aware, to two papers, one by Herr Martens, of Berlin, contributed to the Verein zur Befoerderuny des Gewerbfleisses and the other a lecture by Dr. H. C. Sorby of Sheffield. Dr. Sorby, it seems, was induced to investigate the subject as bearing on the structure of meteoric iron ; and the results he obtained are certainly very interesting. At the Boston meeting of this Institute, in February, 1883, Mr. J. C, Bayles called attention to the subject in a neat and exceedingly interesting paper, in which the work of Messrs. Martens and Sorby was summarized,* and original suggestions were added. It is at present difficult to say what will he eventually the practical value of the microscope, thus employed, in the sciences of engineering. The role which it seems most likely to play is that of' an adjunct to the testing-machine, and not (as some have supposed) a rival to the chemical laboratory. That it will be a most valuable accessory seems, to say the least, highly probable. I need hardly go at length into the details of preparing the material for examination. Mr. Bayles has described the process in such a plain and comprehensive manner that if his instructions are

Jan 1, 1886