Search Documents

By J. R. Stone, G. D. Storm

Design features and operating methods of ASARCO's new unit for the continuous melting and casting of tough pitch copper at Perth Amboy are described. Preliminary studies made for determinitzg economic feasibility and design details are also presented. Cathodes are preheated with oil and melted in an electric furnace at 40-ton per hr rate, from whence the molten copper is fed simultaneously to the wire bar casting wheel and the continuous casting of cakes and billets. In the early 1950's the copper refining furnaces at ASARCO's Perth Amboy plant reached a point where major expenditures would have to be made for replacement of the furnaces and the auxiliary equipment. The problem was whether to continue with the standard reverberatory furnaces or to consider continuous melting in electric furnaces. Reverberatory furnaces have been used for years in the copper industry and for some 50 years at the Perth Amboy plant. Reverberatory melting practice, however, imposes certain restrictions. First, labor costs are high, usually requiring three shifts per day. Secondly, they operate on a batch basis, the conventional operation being a 24-hr cycle including

Jan 1, 1961

By C. W. Tomlinson

INTRODUCTORY THE analyses which have been made by the writer according to the method described below were made as part of Professor Withey's investigation of the concrete aggregates' of Wisconsin, in the hope of throwing light on the extent and nature of the influence of the mineralogical constitution of aggregates upon the properties of the concrete, and mortar made from them. This method was found most satisfactory after four weeks of experiment and modification. It attains an accuracy quite sufficient for the purpose of the analysis, and is fairly rapid. Mineralogical analyses may be thus made at a cost considerably less than that of chemical analyses of a similar degree of completeness. The results obtained by this method should not vary in any item by more than 1 per cent. of the total weight of the sample, and may be made very much better than this by the exercise of greater care in the microscopic counting (see below). The accuracy of the hand sorting 'is of course dependent upon the experience and carefulness of the analyst. . After a month's practice, the writer was enabled to turn out these analyses at the rate of four in 33 hr. of working time. It was found most economical to handle four samples at once. The samples analyzed weighed froth 290 to 340 g. each. The same method could be applied to larger or to smaller samples, within reason able limits. The following list covers the necessary apparatus and equipment: 1 good balance capable of weighing accurately to tenths (or, better, hundredths) of a gram, and of handling quantities up to 200 g. in weight. 1 Westphal balance, registering densities to two or three decimal places. 1 Meker or Bunsen burner, and gas supply. 1 nest of sieves, 10, 20, 40, and 100 meshes to the inch.

Jan 5, 1915

By J. Jolly, R. V. Wheeler

This short note on the probable character of the organic sulfur compounds in coal can do no more than indicate lines of research. We have no new experimental work to describe, nothing comparable in value with the careful studies of American coals by Powell and Parrl and Yancey and Frazer. A study of the manner in which sulfur compounds exist in British coals (and their behavior on heat treatment) is rendered increasingly necessary by the fact that the British reserves of good coking coals of reasonably low sulfur content are fast being depleted. We believe that it is essentially by a study of the modes of formation, occurrence, and decomposition of the various types of inorganic and organic sulfur compounds in coal that it will be possible, with hope of success, to attack the problem of purifying coals, otherwise eminently suitable for coking, from these objectionable ingredients. Sulfur, so far as is at present known, does not normally occur in the free state in the coal conglomerate, but is chiefly distributed, irregularly, in three forms : 1. As primary constituents of the coal conglomerate, organic in nature and probably associated with those molecular complexes that have resulted from the degradation of the proteins of the plant tissues responsible for the formation of the coal mass. These constituents can be classed as "organic sulfur." 2. As metallic sulfides, e.g., iron pyrites. 3. As metallic sulfates, e.g., calcium sulfate and ferrous sulfate. (The occurrence of these compounds varies with the occurrence and degree of degradation of class 2.) It is usually found that sulfur compounds of class 3, the metallic sulfates, are present in coal in small proportions only, amounting to about 1 or 1.5 per cent. of the total sulfur. The compounds in classes 1 and 2 are therefore of more importance. Class 1 alone will receive considera-

Jan 1, 1925

By C. W. Tomlinson

The analyses which have been made by the writer according to the method described below were made as part of Professor Withey's investigation of the concrete aggregates1 of Wisconsin, in the hope of throwing light on the extent and nature of the influence of the mineral-ogical constitution of aggregates upon the properties of the concrete and mortar made from them. This method was found most satisfactory after four weeks of experiment and modification. It attains an accuracy quite sufficient for the purpose of the analysis, and is fairly rapid. mineralogical analyses may be thus made at a cost considerably less than that of chemical analyses of a similar degree of completeness. The results obtained by this method should not vary in any item by more than 1 per cent. of the total weight of the sample, and may be made very much better than this by the exercise of greater care in the microscopic counting (see below). The accuracy of the hand sorting is of course dependent upon the experience and carefulness of the analyst. After a month's practice, the writer was enabled to turn out these analyses at the rate of four in 33 hr. of working time. It was found most economical to handle four samples at once. The samples analyzed weighed from 290 to 340 g. each. The same method could be applied to larger or to smaller samples, within reasonable limits. The following list covers the necessary apparatus and equipment: 1 good balance capable of weighing accurately to tenths (or, better, hun- dredths) of a gram, and of handling quantities up to 200 g. in weight. 1 Westphal balance, registering densities to two or three decimal places. 1 Meker or Bunsen burner, and gas supply. 1 nest of sieves, 10, 20, 40, and 100 meshes to the inch.

Jan 1, 1916

By H. C. Heard

INTRODUCTION As the world's population expands and nations struggle to better their relative position and standard of living, increased emphasis is being directed to the exploration and production of mineral resources, to the mitigation of natural hazards such as earthquakes and volcanic eruptions, and to geotechnical engineering projects such as high-level nuclear waste disposal, underground military facilities, and transportation tunnels. Several topics are common to all of these endeavors. One is the characterization of the rock mass in situ, including the definition of the initial environment (e.g., temperature, stress, etc.). A second is, depending upon the use of the underground or the desired result, the manner in which the boundary conditions or the environment are to be changed by man. Next, the physicochemical behavior of the rock mass must be measured, or inferred with uncertainty limits placed on this behavior, over the appropriate range of environmental conditions (e.g., temperature, chemistry, etc.) for the application proposed. And last, an appropriate, validated predictive model must be applied to estimate the rock mass response to the perturbation. In the period preceding about 1955, only relatively simple testing of soils and rocks was commonplace, partly because the environment (depth) to which these data were applied was not so extreme as it is at present and partly because less precise predictions of material response were acceptable. Only limited and relatively simple test data seemed to be needed to guide the engineering. At the present time and certainly in the future, as we extend our interaction with the earth's crust to greater depths and impose more extreme perturbations on it, we need a larger body of data, deter- mined under much more complex conditions, in order to make the required predictions. The present societal problem of high-level radioactive waste disposal is a case in point. We in the rock

Jan 1, 1982

By Sherwin F. Kelly

THE geophysical scene shifts and alters, the emphasis changes, and new possibilities loom, but the tendency is always towards widening the field and deepening the analytical penetration. Seismic methods have had their heyday, the torsion balance is being displaced by the gravimeter, electrical methods are showing deeper penetration, soil analysis is the newest tool, and gamma-ray logging appears on the horizon. One of the striking features of re- cent geophysical work in the oil fields has been the marked decrease in the number of seismic crews employed. Although the percentage of company crews is believed to have increased appreciably. the sum total has fallen sharply, as shown by the figures for the Gulf Coast area. About two years ago probably over 100 seismic parties were operating there, whereas now there are only about 35. This decrease may be partly due to the low prices of petroleum with a consequent reluctance to spend money to increase crude-oil re- serves but more probably to the fact that reflection and refraction shooting have been carried on so extensively that they have been applied to a large pro- portion of the areas in which they may reasonably be expected to succeed. Some of the earlier enthusiasm, particularly over reflection prospecting, may have erred on the side of over- optimism; some of the present curtailment may be due to over pessimism; but in the opinion of various observers seismic work at the present rate seems to be at it- optimum. It nevertheless remains pre-eminent as a technique for detailing structures in areas where good reflections can be obtained and is the only method that will give accurate depth to definite beds. Results may be poor in certain areas but many regions still remain wherein it can be applied, so that plenty of structural mapping remains to be done by the reflection seismic method.

Jan 1, 1940

By SIDNEY ROLLE

ACURSORY glance through the literature on the subject reveals that the ablest minds in the land are devoting themselves to the great question of labor, of which employment is one of the fundamentals. Volumes have been written and the end is not in sight. Employment management is today about in the position that efficiency was 15 years ago. During the early days of the war, and perhaps for a year or so before, labor was plentiful. As the war progressed and Europe drew on us for munitions, employers began to compete with one another for', all, classes of labor. Labor was difficult to obtain, wages rose, the labor turnover increased, and employers began to install employment departments, welfare plans, and all sorts of schemes, but the labor efficiency dropped. As the war progressed, greater and greater production was demanded. New factors were introduced each day. The government, labor unions, industrial councils, all tended, it seemed, to make the situation almost intolerable. Wages rose to fantastic heights, the cost of living rose higher and higher, and the efficiency dropped still further.

Jan 1, 1921

By Roy J. Helfinstine

One of the most urgent needs in the field of coal combustion is the ability to predict the performance of a coal from knowledge gained from small-scale tests. Numerous types of analyses and tests are conducted on coal, including the proximate and ultimate analyses, heating value, varieties of sulphur, ash analysis, ash fusion temperatures, free swelling index, petrographic analysis, and Gieseler plasticity. The Illinois Geological Survey has made an intensive study of the value of these tests for judging the performance characteristics of the coal as actually utilized. To date, three reports 1 2 3 have been is- sued, and another is being prepared. The present paper briefly summarizes some of the results found in the studies.

Jan 1, 1949

By D. P. Koistinen, K. E. Beu

THE application of the integrated intensity X-ray diffraction method to the measurement of retained austenite concentrations in hardened steels has been fully described.'-' In developing this particular method, the assumption was made that the samples used would have flat surfaces which were free from voids and in which austenite was homogeneously distributed. The original calculation procedure' was modified to include the constant factor G which relates the intensity of a given diffraction line to the concentration of the component giving rise to that line. In order to include A (0) in the constant factor G, it was further assumed that the geometrical conditions relating the X-ray beam, camera cylinder, and sample surface were precisely met.V has been demonstrated that these geometrical conditions can be met experimentally without difficulty in many cases;' however, for those samples which have irregular surfaces or where it is impossible to locate the sample in the proper position with respect to the X-ray beam and film cylinder, it is desirable to evaluate experimentally what effect these nonideal conditions have on the reliability of the austenite determination. This note decribes the results of such experiments. SAE 1095 bar stock was used throughout and all samples were heat-treated as follows: 1600°F for 1 hr in a neutral atmosphere, brine quench, and 300°F temper for 30 min. To control heat-treatment conditions as closely as possible, all samples were plated with 0.002 in. copper to protect the immediate surface from the heat-treating atmosphere. After heat treating, the samples were deplated electroly-tically so that only the copper was removed. The heat-treated surfaces thus obtained were nearly as bright and polished as the original surfaces before copper plating although no mechanical work was done on the samples after heat treating.

Jan 1, 1954

By HENRT M. HOWE

IN my original paper, Piping and Segregation in Steel Ingots, I pointed out1 among other things that, in view of the slighter stretching (virtual expansion) of the crust, and greater opportunity for sagging, there should be less piping in broad than in narrow ingots, and less in slowly-cooled ingots, e.g., those cast in pre-heated sand molds, than in those which cool quickly, e.g., those cast in iron molds. A. A. Stevenson2 said that neither of these predictions agreed with his own experience. In particular, in a picture which he showed of a wide and of a narrow ingot cast from the same ladleful of steel,, the wide ingot had certainly piped much more deeply than the narrow one. At the time I did not see the explanation of these discrepancies, but further reflection makes it evident. One of the most important elements in determining the depth of the pipe is the degree of " top-lag," that is, the degree to which the solidification of the top of the ingot lags behind that of the bottom. 'Through this lagging the steel of the upper part of the ingot is able to run down and fill the pipe below as fast as it forms. To the importance of this lagging I called attention in my original paper.' Sand vs. Iron Molds.-If we compare two like ingots, one cast in an iron and the other in a sand mold, we see that the top-lag' is much greater in the former than in the latter, be¬cause in the former the lower part of the ingot is cooling off fast while the metal is running into the upper part. It is perhaps easier to look at this as a case of the solidification of the hot-

Dec 1, 1909

By Holt, Grover J.

PRIOR to :1937 any discussion of mining and transportation in the iron mines of Minnesota would have been limited largely to conventional methods which have been used for years in the iron ore industry. Today, however, an inspection trip to the crest of almost any open pit on the ranges will re- veal great progress underground mining and the transportation of underground ore have also developed rapidly and if and when underground mining of iron ore again becomes generally economically feasible; these mining methods will probably witness a transformation equal to that which has taken place in the open pits.

Jan 1, 1941

By H. A. Baumann

Experimental data are presented showing the influence of size consist and firing rate upon the performance of bituminous coal-fired, single-retort, industrial underfeed stokers. Size segregation, degradation, and distributor data are also included. The conclusion is reached that size consist of the fuel as fired, is a critical factor in its performance on this class of equipment.

Jan 1, 1950

By Henry M. Howe

In my original paper, Piping and Segregation in Steel Ingots, I pointed out1 among other things that, in view of the slighter stretching (virtual expansion) of the crust, and greater opportunity for sagging, there should be less piping in broad than in narrow ingots, and less in slowly-cooled ingots, e.g., those cast in pre-heated sand molds, than in those which cool quickly, e.g., those cast in iron molds. A. A. Stevenson said that neither of these predictions agreed with his own experience. In particular, in a picture which he showed of a wide and of a narrow ingot cast from the same ladleful of steel: the wide ingot had certainly piped much more deeply than the narrow one. At the time I did not see the explanation of these discrepancies, but further reflection makes it evident. One of the most important elements in determining the depth of the pipe is the degree of " top-lag," that is, the degree to which the solidification of the top of the ingot lags behind that of the bottom. Through this lagging the steel of the upper part of the ingot is able to run down and fill the pipe below as fast as it forms. To the importance of this lagging I called attention in my original paper.' Sand us. Iron Molds.—If we compare two like ingots, one cast in an iron and the other in a sand mold, we see that the top-lag is much greater in the former than in the latter, because in the former the lower part of the ingot is cooling off fast while the metal is running into the upper part. It is perhaps easier to look at this as a case of the solidification of the hot-

Jan 1, 1910

By Meredith Johnson

THE year 1924 saw little change in the production of oil and gas it either Pennsylvania or New York. In the early months of the year the price of Pennsylvania crude oil, $4.00 to $4.50 a barrel, was sufficiently high to cause operators to lay plans for rather extensive drilling opera-tions. But when, in August, the price dropped to $2.85 a barrel, there was no inducement for new work and drilling was curtailed. In spite of the curtailment, however, the combined production of the two states for the year showed a slight increase over 1923, the production being 8;859,000 bbl. in 1923, and 8,901,000 bbl.1 in 1924. The increased production was due entirely to. the continued development of flooding operations in the Bradford field, all other oilfields showing a decline for the year. TABLE 1. Production of Crude Oil in Pennsylvania and New York for the Last Ten Years a Production, Barrels Production, Barrels Year Year Pennsylvania I New York Pennsylvania I New York 1915 7,838,000 888,000 1920- 7,438,000 906,000 1916 7,593,000 874,000 1921 7,418,000 988,000 1917 7,733,000 880,000 1922 7,425,000 1;000,000 1918 7,408,000 809,000 1923 7,609,000 1,250,000 1919 8,137,000 851,000 1924 7,535,0006 1;366,0006 a U. S. Geological Survey figures. b Estimated. Much of the drilling in the southwestern part of Pennsylvania was done in search of gas. Natural gas in Pennsylvania is fast being recognized at its true worth and the increased prices allowed 'the gas companies for their product induced quite a bit of new work. The relative importance of natural gas compared with manufactured gas is shown in Table 2.2

Jan 3, 1925

By Robert T. DeGavre

The $650 million financing for Into Ltd.'s Soroako nickel project is a story worth telling-not only because the project itself represents a significant achievement but also because there are certain important lessons that can be derived from our experience in financing the project. A critical appraisal of the methods and successes in the financing plan is presented in this article, in light of goals which Inco sought to achieve. A technical assessment of the project is not included, since Inco Ltd. has submitted a series of papers on this subject at the International Laterite Symposium as part of the 108th Annual Meeting of AIME in February 1979. Progress in developing and financing the project is encapsulated in the accompanying project factsheet.

Jan 3, 1979

By J. A. Holmes

SHUTTING-IN the Rangely gas well was an interesting problem because of the high rock pressure and the volume of gas developed, as well as the difficulties encountered. After nearly a week's open flow, the rock pressure was 1275 lb., which corresponds with a 2950 ft. hydrostatic head. The volume of gas was between 45,000,000 and 50,000,000 cu. ft. per day. The Rangeley oil field, which now has a daily production of 100 bbl. of shale oil from shallow depth, lies approximately 100 miles north and 30 miles west of Grand Junction, Colo.; not far from the Utah line. The, well we are considering was drilled on the apex of a large clearly defined. Structure1 in the SE.1/4 sec. 30, T. 2 S., R. 102 W., and entered the gas sand at 2954 ft. on March 2, 1925. The condition of the well at the time the gas was encountered was as follows: 20 ft. of 20-in. conductor cemented with ten sacks at 40 ft. The 15 1/2-in. casing was pulled when the 12 1/2-in. was cemented. 1166 ft. of 12 1/2-in. casing, cemented with fifteen sacks. 2531 ft. of 10-in, casing, cemented with ten sacks; neither the 12 1/2-in. nor the 10-in, casing shut off water but they were cemented for protection. 2938 ft. of 8 1/4-in. 36-lb. casing, hanging on a spider in the collar with a forged-steel, high-pressure bradenhead between it and the 10-in. casing. An 8 1/4-in. drilling, or master, gate and a control head were in place on the 8 1/4-in. casing, and all was in readiness for the bringing in of the well.

Jan 1, 1926

By A. E. Bibb, F. W. Kunz

A platelet form of zirconium hydride was found in zirconium and ZY-1 wt pct U single crystals containing hydvogen in the range of 50 to 100 ppm. The habit planes for the hydride plateletg in the zirconium crystals were found to be {1012}, {1121}, and (1122) while the habit planes in the ZY-1 wt pct U crystals were {1121), {1123}, and (1.231). With the exception of the {1231} plane, these have been identified as the twin planes in zirconium. The different effect of hydridc on the mechanical puoperlies of zirconium at high and low strain rates has been explained in terms of the defornzation mechanism and the habit planes of the hydride. ZIRCONIUM and zirconium-base alloys are considered for many nuclear reactor applications, where the pick-up of hydrogen is a distinct possibility, if not an unavoidable occurrence. An excellent example of this is the absorption of hydrogen by zirconium and its alloys during aqueous corrosion, where as much as 30 pct of the hydrogen produced by the corrosion reaction is picked up by the metal. Under the proper conditions, the absorbed hydrogen would precipitate as zirconium hydride and consequently alter the mechanical and physical properties of the zirconium-base alloys. The knowledge obtained from a study of the crystallographic aspects of the hydride precipitation is necessary for the interpretation of the observed changes in the mechanical and physical properties. The deleterious effect of hydrogen on zirconium-base materials is not always observed in normal slow tensile loadings at or above room temperature, but becomes immediately obvious under impact loading, where the energy absorbed decreases with increasing hydrogen content,' and in notched specimens where triaxial loadings are attained.2 This effect is of serious consequence in the applications of Zr where shock loads or high strain rates are experienced. The purpose of this investigation was to determine the crystallographic planes of the Zr and Zr-1 wt pct U matrices upon which zirconium hydride will precipitate and to correlate these with the observed mechanical property data. PROCEDURE Crystal Growth—Single crystals of Zr and Zr-1 wt pct U alloy were used in this investigation. The Zr crystals were made from sponge that had a typical analysis as shown in Table I. Large grains were grown in this material by rapid cooling an arc-melted charge in a button furnace. This operation undoubtedly lowered the volatile impurity concentration below those listed in Table I. Back-reflection Laue patterns of these large grains showed the presence of considerable substructure and lattice distortion within each grain. It was found that an 18-day anneal in an argon atmosphere at 840°C (a high a heat-treatment) followed by furnace cooling, resulted in the further growth of the large grains and removed the detectable substructure ana lattice distortion. Equiaxed crystals with a cube edge of approximately 1/4 in. were produced in this manner. Large crystals of Zircaloy-2 (1.5 wt pct Sn, 0.15 wt pct Fe, 0.1 wt pct Cr, 0.05 wt pct Ni) also were produced by this technique but the large amount of substructure formed could not be removed by annealing. The Zr-1 wt pct U solid solution crystals were produced from an alloy rod consisting of Westing-house-Foote hafnium-free crystal bar zirconium and depleted uranium. The chemical analysis of the alloy is also given in Table I. Three-inch sections were cut from an 0.120-in.-diameter alloy rod and tapered to a fine point on each end. The samples were sealed in evacuated Vycor tubes, homogenized for 5 hr at 1000°C in the ß-phase field, and slowly lowered in a gradient furnace into the a phase (800°C), annealed for 60 hr at this temperature to produce grain growth and furnace cooled. This technique produced large grains approximately 1/2 to 3/4 in. long over the entire cross section of the rod, which were free of observable substructure. Metallographic examination up to X1000 did not show the existence of any second phase in these grains. Crystal Orientation—All crystals were abraded on fine emery paper to produce two flat surfaces 90 deg to each other. The crystals were analyzed by the standard Back-Reflection Laue technique to obtain the crystal orientation with respect to the abraded surfaces. The Back-Reflection Laue Photograms of all crystals used were clear and sharp indicating that the crystals were free from any substructure that could be detected by these means. Hydriding—Only samples containing four to five grains were used for hydriding. Samples that exhibited fine grained patches were discarded. The samples were hydrided using the following technique. After etching in 48 vol. pct HNO3, 48 vol. pct H2O, and 4 vol. pct HF (48 pct) solution, the specimens

Jan 1, 1961

By Gordon S. Duncan

(New York Meeting, February, 1912 THE U. S. Geological Survey, I believe, has almost completed a study of the Harney Peak quadrangle, preliminary to the publication of a report on that, district. As I was engaged for some months on an investigation of the mode of occurrence of the ore-bearing formation in this area, it has seemed to me timely to make public the results of my study, as a contribution to the consideration of this subject. It seems scarcely necessary to describe the locality and general geology of the Black hills of South Dakota, for since 1846 many have contributed information concerning this region, some of the reports bearing such well-known names as those of Walter P. Jenney, Henry Newton, S. F. Emmons, and C. R. Van Hise, while we have only to glance at Bulletin No. 4 of the South Dakota School of Mines, in which Prof. C. C. O'Harra, of that institution, has given us a bibliography of contributions to the geography and geology of the section, to find that other well-known men have studied the district, and have given us the benefit of their researches. The U. S. Geological Survey has made geological maps of nearly the whole of the Black hills, the only quadrangle yet to be completed being, as stated, the Harney Peak district. During the late summer and autnmn of 1910, it was my lot to examine and report. on a considerable area in this neighborhood, which once had been prospected, and in some cases exploited, for tin. This paper gives an account of certain geological phenomena, noted at that time, which greatly influenced my conclnsions. The predominating formation of the district is pre-Cambrian, represented by a highly-cleaved mica-schist, usually very garnetiferous, and sometimes hornblendic. Rising like an island from the surrounding schist is a large mass of granite, known as

Jul 1, 1912

By Albert Sauveur

IN an important paper on The Critical Ranges of Pure Iron1 presented at the May, 1913, meeting of the Iron and Steel Institute, Professor Carpenter reports and illustrates the results obtained by him in determining the critical points of some very pure electrolytic iron sheet about 0.01 in. thick. The iron strip was rolled into the form of a cylinder 1; in. long and fn in. wide, weighing 42 g., the thermo-couple being inserted in a small hole in the center. The points Ac3 and Ar3 were readily detected, as well as the point Art, but the point Act was absent from every heating curve. The author concluded from this occurrence that the conception of A2 as an independent allotropic change must be abandoned. At the October, 1913, meeting of the American Institute of Mining Engineers, Dr. G. K. Burgess and J. J. Crowe read a paper on The Critical Ranges A2 and A3 of Pure Iron2 in which they described some extremely important experiments conducted by them at the Bureau of Standards, Washington, D. C. They tested Professor Carpenter's electrolytic iron and detected a sharp and well-defined absorption of heat corresponding to the point Act. Professor Carpenter's failure to detect this point is explained by them on the ground that unless the iron be in a single piece entirely surrounding and in contact with the thermo-couple junction, the thermo-couple will integrate the irregular progress of the heat through the sample and the curves will lose their sharpness. In discussing Messrs. Burgess and Crowe's paper, Professor Carpenter accepted this explanation as probably accounting for the absence of Act in his heating curves.

Jan 2, 1914

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