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Jan 1, 1945

By John D. Nelson

Jan 1, 1985

By J. R. Long, E. T. Hayes, D. C. Root, R. S. Dean

The U. S. Bureau of Mines has recently reported on the development of a process for preparing pure ductile titanium in substantial quantities1 and on the physical properties that may be attained in the metal, when consolidated by powder metallurgy methods and fabricated by certain hot and cold-working procedures.2 The high physical properties (Table I), combined with excellent corrosion resistance and light weight, will lead no doubt to appropriatc applications of the metal. In any application, methods of joining will be of considerable importance. The relatively high activity of the metal toward the common gases raises the question of weldability and conditions that might be required for successful welding. Since hydrogen, oxygen, and nitrogen embrittle the metal, it should be protected from these gases at elevated temperatures. This was demonstrated by a few preliminary trials of arc, gas, and resistance welding. In these trials only the resistance method proved to be immediately- applicable. While atomic: hydrogen welding of titanium may be successful in some instances, a considerable amount of development work will be required to prove its worth. In addition, it would be suited only to small assemblies that could be heated subsequently in a high vacuum to remove embrittling hydrogen. Heli-are methods likewise would be limited to small assemblies, which could be completely protected by a helium atmosphere. It was quite apparent that titanium required more protection than was afforded by the normal flow of helium gas used for welding magnesium and aluminum. The hot metal is attacked by oxygen and nitrogen, and the rapid diffusion of the oxide into the metal prevents the formation of a protective coating and requires the helium atmosphere to be maintained until the weld has cooled nearly to room temperature. The preliminary work indicated that titanium could be successfully spot-welded without deterioration of the metal and that the microstructures of the welds were normal, exhibiting good bonding, and no oxidation. The high resistivity of titanium (53 microhms per cu. cm.) suggested that it would behave somewhat like stainless steel and allow considerable latitude in the several welding variables. The results reported here are intended to give a general picture of the effects of varying welding current, welding time, and tip pressure on single spot welds made on several different thicknesses of titanium sheet. The work was undertaken to demonstrate the feasibility of welding titanium rather than as an exhaustive study of spot welding. There are, therefore, a number of factors that will require further investigation to establish the specific controls required for actual applications.

Jan 1, 1947

By Fred C. Bond

The process of comminution by grinding is properly classified as an art, rather than as a science. Like most other operations concerned in ore dressing, or in the treatment of nonmetallic minerals, the mathematical relationships of rock breaking are still obscure, and much disputed. If some basic formula exists, comparable for instance to E = RI in electricity, it has not yet been placed in common use. The absence of such a comprehensive mathematical background undoubtedly is the cause of many inefficient designs and installations, as well as of much poorly oriented experimental work. On the other hand, the mathematical immaturity of the process constitutes an opportunity for a real contribution on the part of those who enjoy mental pioneering. Some of the statements made in any such exploratory work may be little more than opinions, and it is to be expected that some will later be proved untrue; but such an evolutionary development is necessary if we are ever to arrive at the fundamental laws, the discovery of which can change the empirical art into a mathematically exact science. The most significant principle of comminution that we possess is probably Rittinger's law, which states that the work done in crushing or grinding is proportional to the area of the new surface produced. There is an alternative theory, known as Kick's law, which formerly was preferred to Rittinger's but which now is rather discredited. According to Kick, the work done in comminution is proportional to the volume, or weight, of the pieces broken, or to the cube of their diameters, while according to Rittinger it is proportional to the square of the diameters. Careful determinations of size distribution below the limit of sieve sizes1 indicate strongly that under ordinary grinding conditions the amount of new surface area produced is directly proportional to the net power input. Changes in the size ratio between the balls and the particles cause important differences in the proportion of the product that passes a given mesh size, but do not affect the total amount of new surface area; they merely change the distribution of the surface among mesh sizes. The principle of constant surface area is the logical result of Rittinger's law, and it may well have an important bearing on the comminution theories of the future. Formula for Ball Wear Grinding tests have been made in the Allis-Chalmers laboratory for more than 9 years, using a standard charge of mixed balls of different sizes; and a continuous record has been kept of the rates of wear of each size. These results have been combined and plotted in various ways in order to discover the relationship that exists

Jan 1, 1943

By H. E. Dunn, C. M. Cosman, J. H. Brennan

Up to the beginning of World War I, the American ferro-alloy industry was in its infancy and largely dependent on Europe. During that War, capacity was over expanded. Later recovery and commercial and scientific development have resulted in an industry which in 1957 produced 1.8 million tons of ferro-alloys. THE ferro-alloy industry is today an important element of the industrial structure of the United States. Its output is valued at almost half a billion dollars annually and its products are basic not only to National defense but also to the peacetime standard of living. This has not always been so. The ferro-alloy industry from late in the last century has grown from small beginnings, nurtured by the demand for stronger, tougher materials; by the search for steels capable of absorbing severe impact loads and resisting corrosive media and high temperatures; and also by the need for electrical and electronic specialties. Conversely, the ferro-alloy industry has grown because it developed improved steels and alloys by extensive research, and because it was able to show to steel makers the advantages accruing from the more extensive and the more economical use of alloying elements. The industry has grown in scope from producing a few grades of ferro-alloys of the more common metals-manganese, chromium, vanadium, silicon, titanium, tungsten, and molybdenum-until there are today some 150 compositions of ferro-alloys available to the steel maker, including such elements as columbium, zirconium, and boron. In 1912 the industry produced 360,000 tons of alloys valued at about $12,000,000, while 1957 production figures show an output of 1.8 million tons worth $440,000,000. In the United States, the history of an industry is largely the history of the companies making up this industry; hence, this paper will briefly trace the development of the most important ferro-alloy-producing companies. Quite varied have been the reasons that caused the different companies to move into the ferro-alloy field; the Willson Aluminum Co., seeking methods of producing aluminum, succeeded with the production of calcium carbide, and their developing electric furnace skills led them to the production of ferro-silicon and ferrochromium alloys. Willson was the predecessor of the Electro Metallurgical Co. of Union Carbide. Two Pittsburgh undertakers, interested in vanadium as an alloying agent for steel, set about to find a mine and, ranging as far as Peru, fathered American Vanadium Co., the predecessor of Vanadium Corp. of America Experiments of the

Jan 1, 1961

By H. H. Rachford, D. S. Howard

In the withdrawal of fluids from tilted aquifers it is of value to be able to predict pressure patterns during the course of the pressure decline. As an example of this, in the displacement of fluids from oil reservoirs being produced by water-drive, prediction of the reservoir pressure is an important factor in fixing production rate. The prediction of pressure patterns in the depletion of an inclined aquifer has conventionally been made by solving the well known flow equations for the pressure Patterns in a horizontal aquifer, and correcting these patterm for the pressure difference due to the hydrostatic head associated with the vertical distance between a point in the horizontal aquifer and the corresponding point in the tilted aquifer. Inasmuch as the equation describing flow in tilted strata is different from that for horizontal flow. there was question as to the validity of the simple corrective procedure current1y in use. To examine the magnitude of error made using this procedure, an inclined aquifer was chosen for which the error was expected to he large, and the equation for flow in this tilted stratum was solved numerically. The results of the conventional procedure of correcting the solution of the equation for horizontal flow was compared with the solution of the correct equation by studying the difference between predicted pressures by the two methods. Three forms of the hydrostatic head correction were studied. The results for all three forms of the head correction are similar. The error in the approximate solution is quite dependent on the position of the horizontal aquifer with respect to the inclined one. The error is greatest at the producing end ad increases with amount of fluid withdrawn. The magnitude of the errors is not large if a good choice is made for the position of the horizontal datum. The most satisfactory position for the datum in all cases is near or slightly about the mid-point of the inclined stratum. Use of the best approximate method studied with the best datum tested yielded predicted pressures in error no greater than 7 psi. INTRODUCTION The movement of water by expansion from an aquifer to displace fluids from a contiguous oil reservoir was first recognized over 20 years ago.9 Since that time much work has been done to relate this mechanism to reservoir behavior mathematically. The result of this effort on the part of many workers has led to an understanding of underground fluid movement which has enabled us to follow and predict the behavior of the water-drive reservoir. One reason that good progress has been made in the application of mathematics to the study of pressure patterns and water movements in aquifers has been that the differential equation which describes this process is of a relatively simple form. The equation for the isothermal, horizontal, viscous flow of water through homogeneous sandstone is identical with that for the diffusion of heat through homogeneous solids, and this equation and means of obtaining solutions for it with many types of boundary conditions have been studied extensively. That this work has been highly successful is clearly emphasized by the large number of solutions developed for problems of interest both by methods of formal mathemat-

Jan 1, 1957

By J. R. Long, R. S. Dean, D. C. Root, E. T. Hayes

The U. S. Bureau of Mines has recently reported on the development of a process for preparing pure ductile titanium in substantial quantities1 and on the physical properties that may be attained in the metal, when consolidated by powder metallurgy methods and fabricated by certain hot and cold-working procedures.2 The high physical properties (Table I), combined with excellent corrosion resistance and light weight, will lead no doubt to appropriatc applications of the metal. In any application, methods of joining will be of considerable importance. The relatively high activity of the metal toward the common gases raises the question of weldability and conditions that might be required for successful welding. Since hydrogen, oxygen, and nitrogen embrittle the metal, it should be protected from these gases at elevated temperatures. This was demonstrated by a few preliminary trials of arc, gas, and resistance welding. In these trials only the resistance method proved to be immediately- applicable. While atomic: hydrogen welding of titanium may be successful in some instances, a considerable amount of development work will be required to prove its worth. In addition, it would be suited only to small assemblies that could be heated subsequently in a high vacuum to remove embrittling hydrogen. Heli-are methods likewise would be limited to small assemblies, which could be completely protected by a helium atmosphere. It was quite apparent that titanium required more protection than was afforded by the normal flow of helium gas used for welding magnesium and aluminum. The hot metal is attacked by oxygen and nitrogen, and the rapid diffusion of the oxide into the metal prevents the formation of a protective coating and requires the helium atmosphere to be maintained until the weld has cooled nearly to room temperature. The preliminary work indicated that titanium could be successfully spot-welded without deterioration of the metal and that the microstructures of the welds were normal, exhibiting good bonding, and no oxidation. The high resistivity of titanium (53 microhms per cu. cm.) suggested that it would behave somewhat like stainless steel and allow considerable latitude in the several welding variables. The results reported here are intended to give a general picture of the effects of varying welding current, welding time, and tip pressure on single spot welds made on several different thicknesses of titanium sheet. The work was undertaken to demonstrate the feasibility of welding titanium rather than as an exhaustive study of spot welding. There are, therefore, a number of factors that will require further investigation to establish the specific controls required for actual applications.

Jan 1, 1947

By Gary Beerkircher

The mine hoisting equipment that is selected and installed at a mine is the lifeline of the mine, and therefore the proper selection of equipment will save a lot of time and money during the life of the mine. Various types of mine hoist designs &e available today, and each has their advantages and disadvantages. Double Drum Hoists, Single Drum Hoists, Friction Hoists and various special designs of these are available but should only be used on applications where they are suitable. There have been several new drive systems for mine hoists which have come into the picture in the last ten years, and they in turn must be evaluated along with the existing drive systems for each hoist application. It does not make sense to properly select the hoist mechanicals, and then have a drive system that turns out to be a bottleneck. This paper will attempt to cover the above noted systems - both the hoist selection and hoist drive system that will provide the mine with a reliable and economical hoisting system. I. Mine Hoist Types There are two basic types of mine hoists available in the world today: the drum hoist on which the hoist rope is actually stored during the hoisting cycle, and the friction (Koepe), which merely passes the rope over the wheel during the hoisting process. Following is a general outline of each type of hoist and the hoisting applications that they are suitable for. First let us consider the simple Single Drum Hoist. As a Service or Production Hoist with cage or skip in balance with a counterweight, a Single Drum Hoist can efficiently service one or more levels since the location of the counterweight at anytime is not important. As a Production Hoist with skips in balance the Single Drum Hoist is best used for single level hoisting. All rope adjustments for proper spotting must be done manually for the Single Drum Hoist. This has to be done periodically to compensate for rope stretch. A variation of the Single Drum Hoist is the divided drum hoist. If multi-layer winding is necessary the Single Drum Hoist must have a divider to allow a separate compartment for each rope. If a counterweight is used with a divided drum application the counterweight rope can be wound on a smaller diameter (Figure 2). Consequently, it moves a lesser distance than the main conveyance and rope adjustment problems are reduced.

Jan 1, 1975

By John Mark Patek

Knowledge of the relative floatability of silicate minerals is increasing in importance as flotation is being applied to the concentration of nonsulfides. Many silicates are in themselves commercial products amenable to concentration by flotation. Moreover, the selective flotation of other nonsulfide minerals, such as cassiterite, depends largely upon the floatability of associated gangue silicates. Differences in floatability existing between the various silicates have not- been sufficiently appreciated; for example, the feldspars that differ greatly in floatability have generally been merely treated as "feldspar." It was the purpose of the work described in this paper to determine by experiment the differences in floatability between silicates; to investigate the causes for such differences, and to discover a means of predetermining approximate floatability without the necessity of experimentation. Determining Floatability The relative floatability of 20 silicates so selected as to represent all of the more common silicate types1 was obtained by flotation tests enumerated in Table 1. The mineral to be floated was crushed dry on a steel plate, and screened repeatedly during crushing through an 80-mesh screen in order to produce a sand with all grains as close to 80 mesh as possible. The sand was placed in dilute (6N) hydrochloric acid until free of soluble foreign material, and then washed with tap water about ten times in order to remove both acid and fines. The resultant product, which averaged 82 per cent plus 200 mesh, was floated in 50-gram charges in a 50-gram Denver celluloid flotation machine with 0.008 gram of terpineol, and from 0.01 to 0.05 gram of oleic acid in a solution acidified with sulfuric acid. The degree of separation of one mineral from another was determined by counting under a nlicroscope the grains of each mineral, both in the concentrate and in the tailings, and comparing their relative abundance in each. Unless the comparison showed a decided difference in amount,

Jan 1, 1935

By H. R. Brannon, J. S. Osoba

The introduction of the scintillation counter into field use for gamma-ray well logging has provided a new tool with special utility for the deternzination of natural radioactivity of sediments. Previous subsurface gamma-ray measurements have indicated only the total amount of radioactivity of the sediments. With the scintillation counter, the relative amounts of the elements which emit gamma radiation can be determined. Sediments logged included 35 zones in wells located in the Teras Gulf Coast, East Texas, and West Teras. Although the data obtained from measurements made to date are not sufficient to evaluate the possibilities of spectral logging, it appears likely that spectral measurements will yield information of geologic value. INTRODUCTION Although variations in the natural radioactivity of sediments were recognized as early as 1909,1 the appli- cation of such variations to borehole logging was not made until almost 30 years later. A group of Russian workers in the early 1930's were successful in making crude measurements of natural gamma activity in an oil well borehole. The first practical gamma-ray logging system was developed by Howell and Frosch2 in 1939. Induced radioactivity, or neutron, logging appeared soon after the introduction of gamma-ray logging. After early work had demonstrated the potentialities of radioactivity logging, development of sensitive and stable logging equipment for field use followed, so that neutron and natural gamma logs are now run routinely and have proved to be extremely valuable in characterizing subsurface formations. Even though tremendous strides have been made in developing radioactivity logging, it is apparent that the ultimate in the method of logging has not been reached, for, until very recently1 in none of the commercially available logging systems has advantage been taken of the fact that gamma radiation is composed of a spectrum of rays, each ray having a distinct and characteristic energy. An individual gamma ray originates in a single element and has energy determined by the element. The inten- sity of radiation, or number of rays emitted from unit volume in unit time, is determined by the concentration of the element. If it were possible to sort out these gamma rays and assign them to their parent elements, thereby essentially analyzing for the elements, a wealth of new information descriptive of formation material and fluid content would be at hand. For example, if in natural gamma logging, the gammas due to potassium and to the thorium and uranium series were measured individually, data would thus be available on the concentrations of each of the three elements, adding materially to the information content of the log. In contrast, conventional gamma logs measure only a quantity proportional to the combined concentrations of uranium, thorium, and potassium. The naturally radioactive elements occur in sediments in concentrations dependent on source material of the sediment, and through their chemical characteristics, on conditions of deposition,' so that the individual concentrations may be diagnostic for particular formations. These concentrations, particularly if measured in situ, could lead to a powerful tool for correlation and for reflecting environmental conditions under which sedimentation took place. As a correlation tool, individual uranium, thorium, and potassium measurements

Jan 1, 1957

By Fred C. Bond

The process of comminution by grinding is properly classified as an art, rather than as a science. Like most other operations concerned in ore dressing, or in the treatment of nonmetallic minerals, the mathematical relationships of rock breaking are still obscure, and much disputed. If some basic formula exists, comparable for instance to E = RI in electricity, it has not yet been placed in common use. The absence of such a comprehensive mathematical background undoubtedly is the cause of many inefficient designs and installations, as well as of much poorly oriented experimental work. On the other hand, the mathematical immaturity of the process constitutes an opportunity for a real contribution on the part of those who enjoy mental pioneering. Some of the statements made in any such exploratory work may be little more than opinions, and it is to be expected that some will later be proved untrue; but such an evolutionary development is necessary if we are ever to arrive at the fundamental laws, the discovery of which can change the empirical art into a mathematically exact science. The most significant principle of comminution that we possess is probably Rittinger's law, which states that the work done in crushing or grinding is proportional to the area of the new surface produced. There is an alternative theory, known as Kick's law, which formerly was preferred to Rittinger's but which now is rather discredited. According to Kick, the work done in comminution is proportional to the volume, or weight, of the pieces broken, or to the cube of their diameters, while according to Rittinger it is proportional to the square of the diameters. Careful determinations of size distribution below the limit of sieve sizes1 indicate strongly that under ordinary grinding conditions the amount of new surface area produced is directly proportional to the net power input. Changes in the size ratio between the balls and the particles cause important differences in the proportion of the product that passes a given mesh size, but do not affect the total amount of new surface area; they merely change the distribution of the surface among mesh sizes. The principle of constant surface area is the logical result of Rittinger's law, and it may well have an important bearing on the comminution theories of the future. Formula for Ball Wear Grinding tests have been made in the Allis-Chalmers laboratory for more than 9 years, using a standard charge of mixed balls of different sizes; and a continuous record has been kept of the rates of wear of each size. These results have been combined and plotted in various ways in order to discover the relationship that exists

Jan 1, 1943

By L. O. Bacon, D. O. Wyble

THERE has been considerable speculation among mining geologists and mining men in general as to the relative merits of gravity methods in iron-ore exploration. Most of the investigations which have been carried out in recent years have been done by mining companies, and few if any of the results have been published. Three gravity surveys have been made in the Iron River-Crystal Falls area,1,2 one by the U. S. Bureau of Mines, with inconclusive results, and the other two by Radar Exploration Co. for the Cleveland-Cliffs and the M. A. Hanna companies, with results not known to the writers. Both the last-mentioned surveys were detailed investigations, the stations being spaced as close as 10 ft along traverses,1 and were made to determine the feasibility of locating iron ore by gravitational methods. Because of the presence of a large body of ore already extensively drilled, Dr. Harold L. James of the U. S. Geological Survey, Iron River, Mich., suggested that a further test of gravitational methods of exploration be made in the Round Lake area of Iron County, see Figs. 1 and 2. This survey indicated a considerable regional gradient and led to a study of the surrounding gravity field and its relation to the major structural features of the syncline within which the iron formation lies. The southwestern part of Iron County presents a series of hills and hollows elongated in a roughly north-south direction. The bedrock topography is of pre-glacial origin. Relief is moderate; a maximum elevation difference of approximately 350 ft was observed during the survey. Major drainage is dendritic with the larger streams: the Brule to the south, the Paint to the north, and the Iron in the central part. Hills are thickly grown with hardwoods, and lowland areas, not under cultivation, are usually covered by second-growth softwoods. The area covered in this paper includes the southern half of Iron County, Mich., with a deep synclinal basin occupying the central part of the area, and the southeast corner of Gogebic County, immediately to the west of Iron County. The upper Huronian iron formation, slates, and graywackes which form the synclinal basin rest upon a greenstone basement. The basin has not been completely outlined by exposures, drill records or other means, as outcrops are scarce and the thick mantle of glacial drift makes geological investigations extremely difficult. Glacial drift varies in depth up to 300 ft or more. The drift is usually thickest under the hills and is thinnest in the depressions and along drainage courses where most of the bedrock exposures occur. The area over which gravity investigations were made is almost entirely covered by glacial material. Bedrock of the basin consists of a complexly folded series of iron formation, slates, and graywackes. One of the series of slates has a high magnetic susceptibility due to the fine-grained magnetite it contains. This formation can be detected readily by magnetic methods and provides a marker horizon which can be easily followed. The magnetic slates are stratigraphically above the iron formation, and much of the geological interpretation of the area is based upon the magneticc anomalies they produce.

Jan 1, 1952

By H. A. Saller, F. A. Rough

Studies of the V-U system have been made to determine the constitutional diagram. The diagram is fairly simple, since no intermediate phases are formed. Additions of vanadium lower the uranium melting point and allotropic transformation temperatures. The maximum solid solubility of vanadium in uranium is 12 atomic pct and the maximum solid solubility of uranium in vanadium is about 4 atomic pct. WITH the advent of high purity iodide vanadium,' it became of interest to study the alloying characteristics of vanadium and uranium. Alloys were prepared covering the entire system and were studied using a combination of metallographic examination and thermal and X-ray analyses. As a consequence of this work, the V-U constitutional diagram was evolved. In order to prepare suitable alloys for equilibrium-phase studies, it is desirable to have the purest possible starting materials. For this investigation, calcium-reduced vanadium, de Boer process crystal-bar vanadium, and good Mallinkrodt Chemical Co. uranium were used. The first work was done using the best vanadium then available, that being calcium-reduced vanadium produced at Knolls Atomic Power Laboratory. Subsequently, the important features of the diagram were checked using alloys made with crystal-bar vanadium produced at Battelle. These checks are in agreement with the earlier work. Analyses of the starting materials are contained in Table I. Only minor amounts of any impurities were present in either the vanadium crystal bar or uranium. Nevertheless, care was exercised in selecting the uranium for the alloys. The procedure followed was to section the stock into suitable pieces for melting, and macroetch each piece. Only those pieces which appeared to be clean by macroetch examination were used for alloying. Experimental Procedure Melting: Alloys with 0 to 50 atomic pct V were induction melted in beryllia (BeO) crucibles under vacuum of 10 microns pressure or better. A number of remelts was frequently required to insure uniformity of the individual ingots. Although no visible reaction between the alloy and crucible was found in any of these operations, the alloys were checked by spectroscopic analysis. Only trace amounts of beryllium were detected in the alloys. Alloys containing 50 to 100 atomic pct V were arc melted in a water-cooled copper crucible under an atmosphere of helium. A tungsten electrode was used. Ingots of 10 to 15 g were produced readily by turning and remelting a few times. Such small ingots were necessary because high purity vanadium was not available in appreciable quantities at this time. After melting, the ingots were examined metal-lographically for segregation and were consolidated by remelting before fabrication was attempted. Spectroscopic analyses showed that only small amounts of tungsten were picked up during the arc-melting process. Fabrication of Alloys: Alloys containing up to 20 atomic pct V could be fabricated by rolling in air at 600°C with 5 min between passes. After each pass through the rolling mill the alloys were returned to

Jan 1, 1954

By Phyllis A. Lyday

Jan 1, 1985

By W. B. Mather

Literature dealing with rock drilling presents a mass of conflicting data. The principal cause of the confusion is attributed to varying definitions of the hardness factor of rock and cutting media. The future development of more efficient drilling methods demands that this problem be solved. The first step in the solution is the compilation of complete data on the physical properties of rocks.

Jan 2, 1951

By Bain, Edgar C.

THE results are presented of an investigation to discover the fundamental atomic conditions existing in Corson's high-copper alloys hardenable by means of silicide solution and reprecipitation. The study attracted the writer because it offered a very convenient example of the general type of hardenable alloys exemplified by duralumin. Sykes' iron-tungsten and iron-molybdenum alloys and the hardenable lead-antimony. SUMMARY OF RESULTS AND CONCLUSIONS In brief, the investigation shows that very perfect crystallinity exists in the solid solutions prepared at high temperature to contain as much dissolved silicide as possible. The lattice parameter of copper is altered very little by the amount of cobalt, nickel or chromium, and silicon dissolved. The hardening by drawing at a temperature to initiate precipitation of excess silicon and metal produces a remarkable change in the atomistics of the solid solution. The old perfection of crystallinity in the solid solution is destroyed and the new atomic spacings are of variable magnitude even in one grain, and a condition in a measure resembling that found in martensite is observed. Were no particles whatever precipitated by the drawing action, still ample causes for hardness would be in evidence in the solid solution alone. The lack of plane continuity in the crystal grains would oppose slip in a very effective manner. Complete annealing restores the crystalline perfection in large measure. In these alloys even the most sensitive methods failed to reveal the characteristic pattern of the silicide precipitated by the anneal, but this was largely to be expected as the amount is relatively small.

Jan 1, 1927

By SME

A regular feature of the December issue is the abstracts of graduate theses in the mineral industry field presented during the preceding year. The following abstracts were submitted for this second article in the series.

Jan 1, 1976

By Persifor Frazer

COMPARATIVE columns expressing the series of rocks of the lower half of the Mesozoic age in this country and in Europe are not yet definitely established. The following represents a co-ordination of the beds in England and Germany,* with a list of materials to be worked in from this country. † * Cotta, " Geologic der Gegenwart." † Section from York to Dillsburg. Report C, 1875; Second Geological Survey of Pennsylvania.

Jan 1, 1877

Jan 1, 1889

By Charles R. Simcoe

It was pointed out in a recent paper'g that the initial flow stress of as-quenched martensite is very low even in an alloy steel with an M, well above room temperature. It was also shown that the high ultimate tensile strength resulted from a very high rate of work

Jan 1, 1967