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Papers presented at two joint meetings of the Mineral Industry Education Division, Geophysics Committee, the American Geophysical Union and the Committee on College Curricula of the American Association of Petroleum Geologists, at the A I M E meeting in New York on Feb 17 and 18, 1941 At the first meeting, the Musing Geology Committee, the Society of Economic Geologists and the Committee on Applications of Geology of the American Association of Petroleum Geologists also took part [ ]

Jan 1, 1941

Papers presented at two joint meetings of the Mineral Industry Education Division, Geophysics Committee, the American Geophysical Union and the Committee on College Curricula of the American Association of Petroleum Geologists, at the A I M E meeting in New York on Feb 17 and 18, 1941 At the first meeting, the Musing Geology Committee, the Society of Economic Geologists and the Committee on Applications of Geology of the American Association of Petroleum Geologists also took part [ ]

Jan 1, 1941

SECTION I PAGE PAGE Bulletins Wanted v Local Section News xv St. Louis Meeting v Affiliated Student Society Notes.. xviii National Engineering Societies in California's Mineral Resources National Service..: vii ? for War Purposes xix Members in Officers Reserve Corps xi Forthcoming Meetings xx Resolution by Military Engineering ? Library xxi Committee xi Membership. :: xxiv Personal :.. xii Biographical Notice of David H. Employment xiv Browne xliv Alaska Mining and Engineering Institute Committees xlvii Society xv Officers and Directors liv

Jan 6, 1917

Arizona E. P. MATHEWSON, Chairman F. W. MACLENNAN, First Vice-chairman CLYDE E. WEED, Second Vice-chairman E. D. GARDNER, Secretary-Treasurer Box 4097, University Station, Tucson, Ariz. I. H. BARKDOLL HENRY F. EASTER MICHAEL CURLEY R. D. LEISK Boston Meets first Monday each month, October to May, inclusive ROBERT S. WILLIAMS, Chairman GLEN F. JENKS, Vice-chairman F. LEROY FOSTER. Secretary-Treasurer Rooms 6-202, Mass. Inst. of Tech., Cambridge, Mass. HOLCOMB J. BROWN ESPER S. LARSEN

Jan 1, 1936

By James M. Barker

Jan 1, 1985

By Robert E. Tally

CHAUNCEY L. BERRIEN, Butte, Mont. (written discussion).-Having had much actual experience with mine fires which have occurred or have been active in the mines of the Anaconda Copper Mining Co. during the past 4 years and having lately visited the fire zone of the United Verde mine with Mr. Tally, I wish to congratulate him for the success which he has had in controlling this fire and making the mine perfectly safe .for his miners. By this work he is not only keeping the property in operation but is reclaiming many lost orebodies. The ventilation system as described by him is practically the same as that used under my direction at the Mountain View mine fire in Butte in 1913 and at the Pennsylvania fire in 1916. This same system is at present being followed at the Leonard mine to extinguish a fire which has been active for 10 years although bulkheaded. The mining system in the Butte mine, at the origination of these fires was the same as that at the United Verde, namely, square setting .accompanied by the use of much timber bulkheading in the stopes owing to heavy ground. The pyritic content of the ore in Butte is not as high, but on the whole conditions have been the same, with the exception of actual location of the fire in the mine. I agree with Mr. Tally that flooding, the use of C02 or any gas, and the use of steam are all impracticable unless the fire zone can be absolutely sealed. His system of upcast escapement shafts in the fire zone, the use of bulkheads and fans to keep the gases away from the firemen, must be resorted to. By the method lie describes actual stoping may be carried on safely if started from the bottom of the fire and if the fire zone extends to the surface. In other words, the fire zone must be isolated from the rest of the mine by bulkheads and solid ground, with no ground above which can be damaged by spread of fire or caving. The serious fires in Butte have .occurred on or between levels in the mines where it was necessary to prevent their .extension upward, downward and laterally while the work of actually extinguishing them was in progress. This necessitated proper bulkheading should we lose control of the fire, the installation of ventilation similar to Mr. Tally's and the systematic drilling of holes with diamond drills for distributing water on the fire and around it.

Jan 12, 1916

By C. S. Matthews, H. C. Lefkovits

The performance of depletion-type reservoirs at the stage in which the gas is at such low pressure that gravity is essentially the sole driving force has been investigated both theoretically and by use of scaled models. A simple theory is developed which completely explains the scaled model experiments. It also agrees with some field data. When the range of production rates to be considered is less than 25, the theory predicts that the production rate decline curve for homogeneous reservoirs in which there is a free surface will be of the hyperbolic type with n = 2: The theory gives a physical significance to the parameter y. INTRODUCTION This investigation was undertaken to determine a method for prediction of performance of reservoirs where gravity is the sole driving agent. Depletion-type reservoirs fall into this category after the pressure has fallen to some low value. Some examples of this type are found at Healdton ('Oklahoma), Oklahoma City (Oklahoma), Midway-Sunset (California), and East Coalinga (California). Generally the production rate per unit thickness is quite low in such reservoirs, with the conse- quence that this stage is sometimes called the stripper stage. However, per well production rates may be of the order of 50 B/D because of the considerable sand thickness open in some of the reservoirs. In the past, predictions of behavior of such reservoirs have been based on empirical extrapolation of the rate of production to the economic limit. Difficulties arise when new wells are drilled in the field or when production is artificially curtailed, since in such cases the decline rate of individual wells or leases changes and no clear trend can be detected. It was hoped that the present study would lead to improved methods for evaluation of such reservoirs. The study was initiated by building a scaled model for a particular field and by running a number of experiments on this model. Later a simple theory was developed which explained the laboratory results completely. The theory led, as shown below, to a hyperbolic-type decline equation which had been used previously' in a completely empirical manner. THEORY The General Case The problem to be treated here is the following: We are given a homogeneous cylindrical porous reservoir with exterior radius r, wellbore radius r., and height h,, containing, from the bottom up to a height hit oil, some gas, and interstitial water (see Fig. 1 A). The portion of the reservoir between K, and h, is filled with gas at low pressure, with residual oil, and with interstitial water. If at a time t = 0, the level of the oil in the wellbore is lowered to a height h,, what is the production rate from the reservoir at a time to The configuration within the reservoir at some instant

Jan 1, 1957

By Thomas F. Bates

ANALYSIS of the chemical and structural differences in minerals often results in a better understanding of the differences in the geological conditions under which they were formed. The minerals in the kaolinite group differ in the amount of interlayer water and in the nature and amount of ordered and/or random shifting of each 1:1 layer with respect to those above and below it. This paper is a progress report resulting from research on the morphology, structure, and origin of fine-grained minerals, supported by Contract N6onr26914 with the Geophysics Branch of the Office of Naval Research. The purpose of the paper is to present data obtained in the laboratories at The Pennsylvania State College and elsewhere, which reveal some of the details of structure of the minerals in the kaolinite group, and to suggest a number of interpretations that bear upon the conditions of origin of these minerals. Be¬cause most of the work in this investigation thus far has been concerned with the relationships of kaolinite, halloysite (4H2O; endellite), and halloysite (2H2O), must of the discussion deals with these members of the group. The first step in the analysis of the differences in two sets of geological conditions is an evaluation of the differences in the minerals that result. Thus the chemical differences between the montmorillonite and the kaolinite clays corroborate other evidence in support of the view that the montmorillonites are commonly formed when solutions are alkaline and leaching poor, while kaolinite usually is associated with acid solutions and good drainage condi¬tions. It is obvious that the greater the differences in the minerals, the more divergent may be the conditions that give rise to them and the more readily one condition can be distinguished from the other. In the kaolinite group, differences between individual members are small, therefore the differences in condition of origin are presumably subtle and difficult to define. At the same time, the very fact that the minerals differ only slightly makes them more sensitive indicators of the exact conditions under which they and the minerals associated with them were formed. Since clay minerals are being used more and more to evaluate the nature, value, and mode of formation of economic mineral deposits, an attempt to define these subtle differences would appear worth while. For purposes of the present discussion, the minerals nacrite, dickite, kaolinite, the so-called "fireclay mineral," halloysite (4H2O), halloysite

Jan 1, 1952

By Frank J. Anderson

IN the cement region of the Lehigh Valley, a difference of 2 to 3 pct in CaCO3 can make or break a new quarry development, and experience of the Dragon Cement Co. has shown that values of calcium carbonate, as reported from churn drill samples, have been increased as much as 6 pct on the average when the same area was diamond drilled. This calcium carbonate increase consequently lowered the values for silica, iron, and alumina, and made these sections much more attractive. Since 1950, the Dragon Cement Co. Inc. has been engaged in extensive diamond drilling in the local limestone of the Northampton, Pa., region, known as the Jacksonburg formation, and in the Lebanon, Pa., region in the Annville limestone, both of Ordovician age.

Jan 12, 1954

By John L. Baum

Tests show that 50 times the earth's normal field can exist near stacked drill rods. Protection against the effect of these strong fields can be obtained by means of a removable sleeve of common iron pipe. GEOLOGISTS and engineers working around a diamond drill rig have often had the opportunity to observe the magnetic attraction of drill rods pulled out of the hole for core removal. This is sometimes an amusing pastime, but this same magnetic force inadvertently applied to a compass needle can cause it to lose its polarity entirely or to become reverse polarized when placed in the immediate vicinity of stacked rods. The first recommendation, of course, would be to avoid the rods, but in surveying an operating drillhole this is not always possible; therefore steps must be taken to neutralize the magnetic effect of the drill rods. Early in the summer of 1949 the geological department of the New Jersey Zinc Co. undertook at Franklin, N. J., an extensive program of surveying the course of deep diamond drillholes. The majority of the holes were surveyed while in the process of being drilled, and considerable difficulty was encountered. A pattern for the deviation of drillholes had been established for the district from surveys in holes from which the drill rig had been removed. It was observed that a certain operating deep drillhole being surveyed did not fit this pattern. In the resulting confusion of repeated surveys and cementing a plug for wedging operations, the lower 1800 ft of the hole was lost. Because of this incident studies were initiated to determine the source of the difficulties and to develop safeguards against recurrence of faulty surveys. Using a hand magnet easily shows that the polarity of a compass needle can be reversed if rotation of the needle is hindered through tilting of the compass or clamping of the mechanism. Such experiments are not recommended, especially in the case of the clockwork type of instruments. A magnetized hairspring in a clockwork instrument will cause the compass card to assume a periodic motion which will not stop until the clockwork runs down. Routine check readings of instrument north before and after each survey are not always sufficient to catch instances of reversed polarity of the compass needle. Although the majority of instances probably take place while the instrument is being removed from the hole with needle in fixed position, it is demonstrable that a 'luggish needle, weakened during a previous test, can be reverse polarized

Jan 1, 1955

By S. A. Falconer

This paper deals with the practical application of the Dutch State Mines cyclone separator for fine-coal cleaning. The more important operating variables are discussed, and results of a number of continuous- scale tests on various fine coals with a 6-in. cyclone separator are given. Descriptions of the Cyanamid Pilot Plant and the 50 tph Cyclone Separator Plant at the Emma Washery in Holland are included.

Jan 7, 1950

By Eugene Guccione

FOREWORD-In an interview published in the May 1975 issue of MINING ENGINEERING, one of the world's most respected scientists, nuclear physicist Hans Bethe discussed the reliability of nuclear power plants and their unmatched safety record. The Nobel laureate also refuted the anti-nuclear lobby's claims that nuclear plants emit harmful radioactive effluents. When asked whether the US has sufficient uranium resources, Dr. Bethe replied that "it depends on the time of introduction of the commercial and advanced breeder reactors which, in effect, can generate more nuclear fuel than they consume." The United States has enough U3O8 to last until the breeders can take over in 1995, said Dr. Bethe. But lie warned that extensive environmental damage would be caused if "environmentalists" succeed in delaying the development of the breeder. Any such delays, he noted, would vastly increase the demand for U3O8 in conventional reactors; this, in turn, would impose an immense burden on the US uranium mining industry, which would then have no alternative but to mine the low-grade Chattanooga deposits.

Jan 4, 1977

By William Glenn

The Ritchie grahamite-mines of Ritchie county, West Virginia, were situated near the central part of the upper barren coal-measures

Jan 1, 1895

By Samuel E. Doak

The utilization of rotary kilns, of the well-known cement type, for the preparation of iron ores for the blast furnace, has become of considerable economic importance within the past 10 years in certain localities, notably those where the native ores are lean. Such kilns may be used simply for the agglomeration of ores too fine to be charged into the blast furnace (i.e., ores whose, loss in the dust catchers is excessive, and whose fineness is detrimental to the working of the furnace), or for the desulphurization of lump and fine ores the sulphur content of which does not exceed 6 or 7 per cent. The desulphurizing action can be combined with that of agglomeration provided the kiln is sufficiently large. Other processes have been developed for the same purpose, but while I am not able to draw a comparison between them by reason of lack of sufficient data, it is safe to say that the kiln, if properly dimensioned for the character of ore to be treated, will compare favorably in its results, both as to economy and quality of product, with any other process. It is not, however, as well adapted for the treatment of flue dust as is a sintering operation, on account of the large percentage of fine coke contained therein. Any combustible entering the kiln at its feed end renders the process very much more expensive and unsatisfactory on account of the difficulty of controlling the temperature, also because of the rapidity with which long "rings" form, due to the increased heat at the cooler end of the kiln. The greatest value of the kiln at present is in the treatment of pyrites cinder; that is, the residue from pyrites ore after the extraction of the greater part of the sulphur. This cinder, while high in iron content, has too much sulphur remaining in it to be allowed to form a large part of the blast-furnace burden, without further treatment. It will range in metallic iron from 42 per cent., representing a very low-grade cinder from a domestic pyrites, to 64 per cent. of the residue from the best Spanish ore, and the corresponding silica content will vary from the maximum of about 25 per cent. to 11/2 per cent. The residual sulphur depends largely on the type of burner used in the original desulphurization. In general, the leanest original ores retain the greatest amounts of sulphur. In modern practice the percentage of sulphur in the cinder is rarely as great as six, and seldom lower than one and one-half. Average analyses for iron, silica, and sulphur of the cinders that have come under my personal observation are as follows:

Jan 1, 1916

By R. F. Stilwell

There are three things that all coal consumers look for when they burn coal: (1) suitability for their particular requirements and burning equipment, (2) uniformity of shipments, and (3) quality as expressed by heating value and other chemical and physical tests. Suitability, or proper application, is determined generally from previous buying experience. It is a function of (1) the reliability and integrity of the shipper and distributor, (2) of a certain coal field or seam and of (3) uniformity and quality. Quality is limited by the location and geology of the seam and mine, the mining and preparation methods and equipment and the knowledge and ability of the personnel. Uniformity of shipments is in many ways the most important factor in coal selection. Lack of uniformity in chemical quality, size consist and treatment cause most of the customer complaints that arise from faults of the coal shipper. Lack of uniformity destroys suitability and quality standards, causing a large customer turnover, and greatly increases sales expense and reduces the net return to the operator. Oil and gas fuels are more uniform in quality than solid fuels, and there will be more gas and oil competition for coal markets after this war than before, because the size of their market is a direct function of the dimensions of their pipe lines, which have been greatly increased during the war. Present mechanical coal-cleaning equipment based upon gravity concentration has gone a long way toward giving us a coal of uniform ash content. The chart in Fig. I, by Hebley,1 shows the greater uniformity of the ash content of washed coal as compared with that of raw coal. Wide variation in the nature and amount of ash in the coal feed to the washer leads to a coal of non-uniform ash content. Mechanica1 cleaning equipment does not understand such terms as ash-softening temperature, coking properties, size consist and sulphur content. Unless the feed to the washer is uniform, the washed coal probably will not be uniform. Table I shows the ash, sulphur and ash-softening temperature of two mines in the Pittsburgh bed, both raw and washed, loaded over the same tipple; also No. 3 and No. 4 Pocahontas seams, both raw and washed, loaded from the same preparation plant. It is obvious that they must be blended or loaded separately if a uniform product is to be obtained. Why Is Blending Necessary? It was natural for the operators of captive mines producing by-product coals to recognize the necessity for blending raw coals of different quality and coking characteristics. They have had many years of experience with blending high, low and medium volatile coals at their oven plants. They have found that careful blending gives a coke of more uniform quality and better structure. Coals that could not be

Jan 1, 1947

By R. F. Stilwell

There are three things that all coal consumers look for when they burn coal: (1) suitability for their particular requirements and burning equipment, (2) uniformity of shipments, and (3) quality as expressed by heating value and other chemical and physical tests. Suitability, or proper application, is determined generally from previous buying experience. It is a function of (1) the reliability and integrity of the shipper and distributor, (2) of a certain coal field or seam and of (3) uniformity and quality. Quality is limited by the location and geology of the seam and mine, the mining and preparation methods and equipment and the knowledge and ability of the personnel. Uniformity of shipments is in many ways the most important factor in coal selection. Lack of uniformity in chemical quality, size consist and treatment cause most of the customer complaints that arise from faults of the coal shipper. Lack of uniformity destroys suitability and quality standards, causing a large customer turnover, and greatly increases sales expense and reduces the net return to the operator. Oil and gas fuels are more uniform in quality than solid fuels, and there will be more gas and oil competition for coal markets after this war than before, because the size of their market is a direct function of the dimensions of their pipe lines, which have been greatly increased during the war. Present mechanical coal-cleaning equipment based upon gravity concentration has gone a long way toward giving us a coal of uniform ash content. The chart in Fig. I, by Hebley,1 shows the greater uniformity of the ash content of washed coal as compared with that of raw coal. Wide variation in the nature and amount of ash in the coal feed to the washer leads to a coal of non-uniform ash content. Mechanica1 cleaning equipment does not understand such terms as ash-softening temperature, coking properties, size consist and sulphur content. Unless the feed to the washer is uniform, the washed coal probably will not be uniform. Table I shows the ash, sulphur and ash-softening temperature of two mines in the Pittsburgh bed, both raw and washed, loaded over the same tipple; also No. 3 and No. 4 Pocahontas seams, both raw and washed, loaded from the same preparation plant. It is obvious that they must be blended or loaded separately if a uniform product is to be obtained. Why Is Blending Necessary? It was natural for the operators of captive mines producing by-product coals to recognize the necessity for blending raw coals of different quality and coking characteristics. They have had many years of experience with blending high, low and medium volatile coals at their oven plants. They have found that careful blending gives a coke of more uniform quality and better structure. Coals that could not be

Jan 1, 1947

By Thomas T. Read

MINING, which is at least twenty centuries old, was at first, and long, wholly a practical art. Little more than two centuries have elapsed since the inception of the idea that general education and a knowledge of natural science would be of advantage to those engaged in the mining industry. Though schools of mining began to develop in Europe early in the eighteenth century the concept of educational preparation for technical conduct of the industry was slow in winning general acceptance in the industry itself. John Hays Hammond, in his autobiography,1 recalls that when he sought employment with a mining company after he had graduated from Yale and Freiberg he had to assure its executive, before being even considered for employment, that he did not consider that he had learned anything about mining. This was as late as 1880. Existence in the industry of a prejudice against education of the academic type is perhaps an explanation why inadequate provision has been made by the mining industry for the continuing education of technical employees after they enter employment, although engineering education prior to engaging in industry has now won general acceptance. I am familiar with the existence of "loop" courses for engineering graduates in metallurgical plants, of schemes for giving mining graduates "practical experience," and of the interest in vocational courses for workmen which sprang up in the period of labor shortage during and immediately following World War I (but which quickly died when the depression of 1921 again made experienced workmen available in sufficient supply), having been chairman of a committee appointed by the Mineral Industry Education Division to make a survey of existing provisions for post-employment training for engineers in our industry. The results of that survey, reported elsewhere, clearly indicate that it is inadequate as to amount; the aim of this paper is to present evidence for belief that it is also inadequate in quality. To avoid becoming too involved, no reference will be made here to post-employment vocational training for workmen, which is a subject differing so much from post-employment education for engineers as to require separate treatment. Neither will postgraduate education for metallurgical engineers be discussed, because a distinction must then be made between training for research work and for plant operation, whereas mining engineers engage almost exclusively in operations. Since the situation in the coal-mining industry has been discussed at several recent meetings, that also will be passed over, and what follows should be taken as a discussion applying exclusively to the metal-mining industry. PROFESSIONAL DEVELOPMENT In the operations field (both in mining and metallurgy) the work to which a beginner is assigned is seldom closely related to previous academic education. The contrast is almost as great as between

Jan 1, 1941

By Thomas T. Read

Mining, which is at least twenty cen-turies old, was at first, and long, wholly a practical art. Little more than two centuries have elapsed since the inception of the idea that general education and a knowledge of natural science would be of advantage to those engaged in the mining industry. Though schools of mining began to develop in Europe early in the eighteenth century the concept of educational preparation, for technical conduct of the industry was slow in winning general acceptance in the industry itself. John Hays Hammond, in his autobiography, recalls that when he sought employment with a mining company after he had graduated from Yale and Freiberg he had to assure its executive, before being even considered for employment, that he did not consider that he had learned anything about mining. This was as late as 1880. Existence in the industry of a prejudice against education of the academic type is perhaps an explanation why inadequate provision has been made by the mining industry for the continuing education of technical employees after they enter employment, although engineering education prior to engaging in industry has now won general acceptance. I am familiar with the existence of 'loop" courses for engineering graduates in metallurgical plants, of schemes for giving mining graduates "practical experience," and of the interest in vocational courses for workmen which sprang up in the period of labor shortage during and immediately following World War I (but which quickly died when the depression of 1921 again made experienced workmen available in sufficient supply), having been chairman of a committee appointed by the Mineral Industry Education Division to make a survey of existing provisions for post-employment training for engineers in our industry. The results of that survey, reported elsewhere, clearly indicate that it is inadequate as to amount; the aim of this paper is to present evidence for belief that it is also inadequate in quality. To avoid becoming too involved, no reference will be made here to post-employment vocational training for workmen, which is a subject differing so much from post-employment education for engineers as to require separate treatment. Neither will postgraduate education for metallurgical engineers be discussed, becadse a distinction must then be made between training for research work and for plant operation, whereas mining engineers engage almost exclusively in operations. Since the situation in the coal-mining industry has been discussed at several recent meetings, that also will be passed over, and what follows should be taken as a discussion applying exclusively to the metal-mining industry. Professional Development In the operations field (both in mining and metallurgy) the work to which a beginner is assigned is seldom closely related to previous academic education. The contrast is almost as great as between

Jan 1, 1943

By Thomas T. Read

Mining, which is at least twenty cen-turies old, was at first, and long, wholly a practical art. Little more than two centuries have elapsed since the inception of the idea that general education and a knowledge of natural science would be of advantage to those engaged in the mining industry. Though schools of mining began to develop in Europe early in the eighteenth century the concept of educational preparation, for technical conduct of the industry was slow in winning general acceptance in the industry itself. John Hays Hammond, in his autobiography, recalls that when he sought employment with a mining company after he had graduated from Yale and Freiberg he had to assure its executive, before being even considered for employment, that he did not consider that he had learned anything about mining. This was as late as 1880. Existence in the industry of a prejudice against education of the academic type is perhaps an explanation why inadequate provision has been made by the mining industry for the continuing education of technical employees after they enter employment, although engineering education prior to engaging in industry has now won general acceptance. I am familiar with the existence of 'loop" courses for engineering graduates in metallurgical plants, of schemes for giving mining graduates "practical experience," and of the interest in vocational courses for workmen which sprang up in the period of labor shortage during and immediately following World War I (but which quickly died when the depression of 1921 again made experienced workmen available in sufficient supply), having been chairman of a committee appointed by the Mineral Industry Education Division to make a survey of existing provisions for post-employment training for engineers in our industry. The results of that survey, reported elsewhere, clearly indicate that it is inadequate as to amount; the aim of this paper is to present evidence for belief that it is also inadequate in quality. To avoid becoming too involved, no reference will be made here to post-employment vocational training for workmen, which is a subject differing so much from post-employment education for engineers as to require separate treatment. Neither will postgraduate education for metallurgical engineers be discussed, becadse a distinction must then be made between training for research work and for plant operation, whereas mining engineers engage almost exclusively in operations. Since the situation in the coal-mining industry has been discussed at several recent meetings, that also will be passed over, and what follows should be taken as a discussion applying exclusively to the metal-mining industry. Professional Development In the operations field (both in mining and metallurgy) the work to which a beginner is assigned is seldom closely related to previous academic education. The contrast is almost as great as between

Jan 1, 1943

By Thomas F. Donnelly

Discussion of the paper of THOMAS F. DONNELLY, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 104, August, 1915, pp. 1759 to 1768. F. LYNWOOD GARRISON, Philadelphia, Pa. (communication to the Secretary *).-The paper is of value in giving the public some first-hand information regarding a copper property that from various causes has attracted considerable attention, especially in Philadelphia, and which has also been the source of several fantastic flotations that had little to recommend them. Since 1906, no work has been done on this property under my direction, with the exception of a topographic survey made last winter by Mr. Donnelly, which was intended as the first step in a sound and logical system of development. From 1906 to 1915, desultory attempts were made to develop these orebodies, but as the work was not in competent hands much money was wasted and even more disappeared in ways regarding which it is perhaps not best to inquire. The result is, this interesting property has now practically no more ore developed upon it than in 1906, despite the fact that a new 100-ton mill is being erected, although, as I have intimated, it is today not much more than a prospect. Turning now to the scientific and more agreeable side of the subject, it is interesting to note that these Santo Domingo copper ores are invariably found in volcanic tuffs and that, in a geologic sense, they are all very old, for there are no evidences of recent volcanic activity in the greater Antilles, of which this island is the second largest. The existence of copper in tuffs in different parts of the world is a notable fact. Often, if not usually, it is present in mere traces, but not infrequently we find it in sufficient amount to be of economic importance. Thus, for example, chalcopyrite and bornite occur in the Tertiary tuffs of Japan, and a number of producing copper mines of that country are either actually in, or closely associated with, rocks of this character. Whether the copper minerals are original primary ores in the tuffs, or were derived from accompanying eruptive dikes, appears not yet to have been determined in any instance. In most of the Japanese cases of which I can find any record the tuffs appear to be associated with shales and limestones. These Japanese copper ores also carry some gold, especially in the upper parts of the veins; in this they resemble the Santo Domingo deposits which not infrequently carry as much as $6 or $7 per ton of gold on the outcrop. As a rule the content of gold in both the Japanese and

Jan 12, 1915