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By Nath S. Parate

Emphasis on publications related to coal mining subsidence and damages is appropriate at present in view of the energy crisis and increased coal production and public alertness. I have worked in Harrisburg with the state government Public Utilities Commission on energy-fuel matters and issues (Parate, 1978-80). I have participated in the communication on subsidence/ damage reviews and status with the Bureau of Mines Liasion Office (Kebblish, 1978-79). I have done research (Parate, 1965) and published papers (Parate, 1972; Parate, 1967) in Britain on coal mining subsidence and damages around Sheffield-Nottinghamshire coal fields. I have a few comments on the recent paper titled, "Pennsylvania Subsidence Control Guidelines," by C.J. Bise. 1) What is the basis of the empirical formula or guideline, LD _ (0.27 x D) ± 4.6, defining the support area? 2) The particular structure may not be damaged due to vertical uniform displacement caused by mining beneath unless the displacement is differential (King, 1964). 3) The author mentions the limited subsidence research in the US, and quite rightly so. But he fails to quote any work reference by continental investigators except the British or review work by the US. What are the reasons? 4) The author has not mentioned the importance and role of angle of draw for Pennsylvania, Kentucky, or Illinois coal fields. Is there any current research investigation on the relationship between subsidence research investigation, damage, and transference of strains to structures? There have been a number of newspaper reports on subsidence damage in Wilkesbarre and other areas in Pennsylvania. Is the author aware of such instances and traditional attitudes to such issues? Many times government agencies--due to lack of funds, technical expertise, and public policies--are unable or do not find it interesting to keep updates on these issues, as per the author's knowledge and experience with state governments. 5) What is the net effect and role of the D.E.R. Insurance Office on the monitoring, reducing, or controlling subsidence damage, particularly in Pennsylvania?

Jan 1, 1983

By H. Kahata, I. Iwasaki, Y. Takahasi

A combined process of segregation roasting-flota-tion or magnetic separation was developed to recover nickel from lateritic iron ores and oxidized nickel ores. An ore was mixed with a halide, such as sodium or calcium chloride, and a solid reductant, and roasted, whereby the nickel content was segregated out as discrete metallic particles. Either by magnetic separation, or by flotation using a sulfhydryl collector together with a heavy metal salt as an activator, the metallic nickel could be concentrated, Effects of such variables as the types and amounts of the halide and solid reductant addition and of the roasting conditions were extensively investigated. The concentration results on several types of ores from Japan, the Philippines, and New Caledonia are presented. Laterite is a residual product of rock decay in tropical and subtropical regions, and consists mainly of hydrated oxides of iron and alumina. Those derived from serpentine sometimes become enriched in nickel, cobalt, and chromium contents. Oxidized nickel ores are of the similar origin, but their nickel as well as silica contents are higher due to gamierite-type silicates. Apparently, nickel enrichment is more pronounced in the transition region between the surface layer of iron laterite and the underlying serpentine. Iron laterites often contain over 50% iron, and their reserve is reported to exceed 22 billion tons, corresponding approximately to 20% of the world iron ore reserve.1 It is readily apparent, therefore, why the iron laterites have attracted much attention of the steel industry as a potential source of iron ores. Numerous attempts to remove nickel and chromium as byproducts, have been reported in literature.' Worldwide discoveries of high-grade iron ore deposits in recent years have inevitably lessened the interests in iron laterites. However, in view of the tremendous potential for their gross value and supplies of nickel, cobalt, chromium, and alumina along with iron, the problem remains as a challenge. Much of the chromium in laterites is present in the form of relatively coarse particles of chromite, and various classification methods have successfully been applied for its removal.2,3 The nickel, however, is intimately associated with limonite, and ordinary concentration techniques are totally ineffective. Much attention has, therefore, been given to hydro-metallurgical or pyrometallurgical means. Yet, all the known processes appear to have limitations either economically or for the use of products as iron raw materials due to a high residual content of nickel. Some attempts have been made to pre-roast laterites or oxidized nickel ores, particularly with sulfidizing agents, and to remove nickel either by magnetic separation,' or by flotation.4 It is apparent that any such concentration process would require grain growth of nickel during roasting for effective separation. Oxidized copper ores are reported to be concentrated by the segregation roasting-flotation process,5 in which the ores are roasted with a chloridizing agent and a carbonaceous reductant in order to promote the growth of metallic copper through repeated cycles of copper chloride volatilization and its reduction on the solid reductant surfaces. Examination of a vapor pressure-temperature diagram of various metal chlorides indicates that a separation of nickel from iron may be effected by a similar process. In fact, the segregation roasting of laterites was reported to increase the extraction of nickel by the ammonia leach process, as compared to the ordinary reduction roasting.6 In the present article some of the preliminary experimental results of the segregation roasting, followed by either flotation or magnetic separation, on laterites and oxidized nickel ores are reported. The effects of various parameters in the roasting as well as in the concentration steps are discussed. MATERIALS AND METHODS An oxidized nickel ore from Thio, New Caledonia, and three laterites from Homonhon, the Philippines, Wakasa and Miyagawa, Japan, were selected for the

Jan 1, 1967

By J. P. Kerr, W. N. Logan

Lack of reliable and detailed information on many of the older fields in Indiana has necessitated the use of x and y in many instances. Even in the younger fields many data were lacking. It was thought that even though much was to be desired regarding the amount and accuracy of the information on the old Trenton field, it was too important to be left out. We trust that we are not perpetuating any of the inaccuracies that are to be found in the data for Indiana.

Jan 1, 1935

By P. L. Weston, S. E. Khalafalla

A systematic study was made by the Bureau of Mines on the effect of so me hypothesized accelerators for the process of wustite reduction in carbon monoxide. When small concentrations of promoter materials in the order of 0.69 at. pct were added to the reducible charge, the rate of reduction to iron was increased. Promotion phenomenon prediction was made in light of a suyface reduction mechanism with the aid of Vol'kenshtein's effect regarding the propagation of crystal lattice disturbances by small amounts of relatively larger interstitial ions. The acceleration produced by a typical promotor, such as potassiunl, increases with protnoter concentration up to a maximum, beyond which the reduction rate decreases. Concentration for maximum promotion depends on the nature and physicochemical properties of the promoter. The extent of reduction rate enhancement is found to be directly proportional to the atomic volume and electronic charge of the additive. DESPITE the enormous volume of literature on iron oxide reduction, very little is reported concerning additive or impurity effects on this important metallurgical process. The beneficial effect bf calcium compound additions on the reducibility of iron oxide sinters has been reported by Tigerschiold,1 vor dem Esche,2 and Edstrom. Doi and Kasai~ found that the addition of lime or limestone to iron ores helps to break up any unreducible compounds, such as fayalite or ilmen-ite. and thus free the combined iron for reduction. Schenck et al. 5 suggested that the increased reduction rate obtained when adding lime could be accounted for by the instability of wustite in the presence of lime. Acid-base slagging reactions resulted in wustite disproportionation according to The dicalcium ferrite formed will yield iron and calcium oxide during reduction. Regenerated calcium oxide dissociates more wustite. This mechanism has been used by Seths and white7 to explain their experimental results. Recently, Strangway and ROSS' attributed the calcium carbonate acceleration of iron oxide agglomerate reduction to increased porosity, both initial as well as that developed during reduction. Aside from calcium carbonate, or oxide, no other promoter was noted in the literature, except for a brief mention by Barrett and woodg on the effect of sodium carbonate and aluminate as activators for the hydrogen reduction of magnetite at 600°C. The present investigation systematically studied a host of other promoters, including calcium and sodium, in an attempt to elucidate the mechanism by which promotion takes place and to fit the results into a simple chemical model. To attain this goal, the effect of promoter physical properties, such as atomic volume, electronic charge, and concentration are related to wustite reduction kinetics in this paper. Wustite reduction to iron, rather than the overall hematite reduction, was chosen since this reaction is known to be the slowest, and hence the rate-deter mining step for the overall iron oxide reduction process. EXPERIMENTAL PROCEDURE Raw Materials and Their Preparation. The pure or impregnated wustite pellets were prepared from minus 400-mesh chemically pure hematite powders. A known weight of hematite was thoroughly and uniformly mixed with a calculated weight of the additive. The mixed paste containing 35 wt pct water was gradually heated from 400" to 1200° C and fired at 1200°C for approximately 4 hr in an air atmosphere. After cooling, the sinter was pulverized to minus 100 mesh and pelletized into minus 4- plus 5-mesh spheres. Pellets were fired, similarly to the paste mix, air-cooled, sized, and stored. An appropriate weight of the charge (20 g) was placed in a zirconia reduction tube maintaining a uniform oxide bed height of 1 cm and a cross section of 7.1 sq cm for all of the test runs. The samples were supported in the vertical reaction tube by a bed of fragmented insulating firebrick plus 3- to 6-mesh alumina beads. The hematite was then transformed to wustite by reduction with a 30 pct CO2-70 pct CO gas mixture at 1000°C in a globar furnace. Complete conversion to wustite was ascertained by a continuous infrared gas analyzer recording the CO-CO2 content of the effluent gas until no carbon monoxide was absorbed from the inlet gas, and inlet-outlet gas analysis remained constant for 30 min. The wustite sample was then reduced with 100 pct CO at 100WC. From the recorded data, an initial rate of reduction was determined by the initial slope of the graph percent reduction vs time. In order to estimate the accuracy of the data, five separate determinations of the reduction curve of pure wustite, under otherwise identical conditions, were performed. The maximum deviation from the average reduction at 14 min amounted to 2 2 pct reduction. This deviation corresponds to 3.8 pct variation based on the percent reduction of the sample. Aiiy impurity effect below the limits of this maximum deviation was considered a spurious result. If the effect exceeded + 4 pct, then it was considered as a positive one. Considerable care was exercised in determining the initial rate from the slope of the initial segments of the curve. Each reduction curve was examined separately on large graph paper and the best tangent to the curve at zero time was drawn. The slope of this tangent was taken as a measure of the initial fractional reduction per minute. Although the time required to reach 50 pct reduction may be of special practical significance, initial rate measurements are invaluable in fundamental studies. These rates provide a measure of the process kinetics on the initial

Jan 1, 1968

THE problem of picking the best students for an engineering college can no longer, be considered as simply one of determining the amount of general ability, but rather of finding special aptitudes for scientific work, according to Carl C. Brigham~ a Princeton University professor, who has been conducting researches on methods of selecting engineering undergraduates at Cooper Union, an evening school in New York City. When we first began this investigation seven years ago," says Dr. Brigham, "we thought the whole job would be done a soon as we had found a good method of measuring general intelligence. Today we feel that we are still about five years away from a solution, but on somewhat firmer footing than when we were looking for general ability.

Jan 1, 1928

By C. W. Volek, J. E. Chappelear

The injection of a hot liquid into initially cool porous media, saturated with the same liquid and surrounded by two impermeable but heat conducting media (cap and base rock), has been studied both experimentally and theoretically. The temperature dependence of the viscosity was included in the theoretical model, but it was assumed that the specilic heats and densities of the various materials were independent of the temperature. Solutions to the theoretical model were approximated by numerical methods. Both theoretical and experimental results indicate that center-line temperatures are significantly higher than boundary temperatures. Comparison of experimental and theoretical results with a cold/hot viscosity ratio 01 19:1 were in reasonable agreement. Theoretical calculations show that the effect of the temperature dependence of viscosity was very significant at ratios of 100:l to 1000:1, which are typical of those that occur when injecting hot water to flood heavy oil reservoirs. INTRODUCTION We consider the problem of prediction of fluid flow and temperature distribution in an initially cold-fluid-filled reservoir on the injection of the same hot liquid by the use of mathematical and physical models. The results reported are for a two-dimensional rectangular section of the reservoir, as shown in Fig. 1. The injection and withdrawal faces are assumed to be equipotentials for fluid flow. The ultimate purpose of such models would be to predict hot-water injection performance. However, we note that in the work presented here, one of the most significant aspects of the problem — the instabilities resulting from two-phase, water and oil flow — is not included. We will not give a historical review, but refer instead to the paper of Spillette and Nielsen,1 which contains a rather complete bibliography and critical discussion. The physical problem is exactly the same as Spillette and Nielsen, except for certain simplifications in our assumptions. The mathematical details are somewhat different, and we will present the details of our method here. The mass flow equation, which is elliptic in character, is handled by successive overrelaxation. The heat flow equation, which is parabolic in character, is handled by a straightforward explicit approximation. Some difficulty arose in the over-all heat balance due to small errors in the solution of the mass flow equation, and we feel that a different formulation of the heat flow equation would be desirable for future work. In addition to the mathematical solutions for the temperature distributions in a porous medium due to the injection of hot liquids, experimental data are presented to check the validity of these solutions. A schematic diagram of the model is shown in Fig. 2. Certain qualitative physical conclusions were obtained from our numerical and experimental results. These are: 1. Assuming high (infinite) conductivity normal to the bedding plane in the reservoir is a poor approximation, and may lead to overestimates of the total heat losses (to cap and base rock) of as much as 50 percent. 2. More heat is retained in the reservoir (per unit of heat injected) for higher viscosity changes. 3. Any particular temperature isotherm moves more rapidly along the center line for higher viscosity changes. Consequently, the approximation of temperature independent viscosity is not suitable for obtaining quantitatively correct results. MATHEMATICAL MODEL Our mathematical model is that of a reservoir of thickness 2h. The problem is idealized from that of a linear hot-water drive, and we imagine that the input face is sufficiently far away from the injection wells that the stream lines enter it normally. Similarly the production wells are far enough from the outflow face that the flow lines leave it normally. The reservoir and surrounding cap and base rock

Jan 1, 1970

By Charles W. Merrill

IF we follow the threads of the mining problems, upon which I have touched, we find them all leading to one great fundamental desideratum. The people of this State, of this Nation, and of this world must be brought to a better understanding of the basic nature of our industry-must be made more mineral-minded. It is my belief 'that there is not a man present among this earnest gathering of those interested in the mining industry, who has not a deep-seated and heartfelt desire that the existing unprecedented welfare and prosperity of the whole mass of American people be maintained not merely through our own generation but through the generations of our children and their children. In the decades to come there can be no question of the keenness of the foreign competition which we are doomed to meet, and in this great international contest that Nation which has the best balanced program of development and that broadness of vision in its governmental direction, which recognizes the necessity of a sympathetic attitude toward the upbuilding of such a broad pro- gram will be the Nation which will maintain and pre- serve that welfare of all of its people.

Jan 1, 1929

By Robert E. Tally

A recorded in the account of the Annual Meeting, on another page, the report of the tellers showed that all men nominated by the committee, which included Messrs. Wilber Judson, E. DeGolyer, W. A. Weldin, J. A. Norden, J. D. MacKenzie, Wilfred Sykes and S. Skowronski, were duly elected to the offices for which they were nominated. Robert Tally, who was elected to the presidency for 1931-2, is well known to all our members not only because he has served on the Board of Directors since 1928, but through a brief outline of his great achieve¬ments in his chosen profession pub¬lished in our issue of December last. The vice-presidents, Howard N. Eavenson and H. A. Guess, are also well known to our members. Mr. Eavenson has not only been chairman of the Coal Division since its organization, but was also a Director during 1917, 1918 and 1919., Mr. Guess was Director in 1926, was elected a vice-president by the Board last year to fill the vacancy created by the election of Mr. Bassett to the presidency, and is now elected to the usual three-year term.

Jan 1, 1931

By AIME AIME

LEADING off the Thursday morning session on Non-metallics was C. E. Heinrichs' paper, "Phosphate Flotation, Its Place in the Technology and Economics of the Phosphate Industry." Mr. Heinrichs also presented a closely related paper, "Milling Methods and Costs at the No. 2 Concentrator of the Phosphate Recovery Corporation," by H. S. Martin. The first of the papers points out the great significance of flotation to the phosphate industry, inasmuch as flotation practically doubles the potential recovery, thereby decreasing production costs and increasing reserves materially. The second paper describes three such plants, two of which are in Florida, the third being at Wales, Tenn. Operating characteristics and costs are reviewed. Answering inquiries from the floor, Mr. Heinrichs said that the adoption of a new parallel-shell dryer, from 60 to 80 ft. long, instead of the old single-shell countercurrent dryer, had increased the unit drying capacity over 300 per cent and had reduced the drying cost to less than 25c. per long ton of dried product. The initial moisture is from 15 to 18 per cent and the final about 2 per cent.

Jan 1, 1933

By Roger E. Barthelemy

PRIMITIVE mining and metallurgy has today almost disappeared. Probably the only remaining tribal tin mining and smelting is practiced by the Laotian natives in one of the less known tin areas of the world. This district lies almost a thousand miles from the sea along the Mekong River, one of the longest rivers in the world, that marks the border between Siam and Laos, one of the five states forming French Indo-China. Less than twenty years ago it took more than two weeks' travel on elephant-back to reach the spot and today it still takes many days of travel, using all kinds of transportation from automobiles to native

Jan 1, 1938

By Harrison Souder

UNDER the stimulus of steadily in- creasing 'demands of the steel industry at home, and with the supply of available ores from abroad appreciably diminished owing to vigorous rearmament campaigns in Europe, production of Eastern magnetite ores reached an all- time peak in 1937. Although the figures given in the accompanying table are partly estimated (actual figures were available for eleven months only), it appears that 1937 production was nearly 47 per cent higher than that of 1936.

Jan 1, 1938

By J. J. Carrigan

DURING the experimental stage in our use of the electric cap lamp in the Anaconda mines at Butte. Mont., we were somewhat concerned as to how the spitting of fuses would be carried out if we completely eliminated the open-flame light. This problem was at once given serious attention by the engineering research department and some thought was given to having all blasting done by the use of electric delays, which has been the practice for some years

Jan 1, 1936

By D. R. Mitchell

FOR the second consecutive year, attendance at the Coal Division sessions far exceeded exoectations. Those in charge were continually faced with problems of finding seats and space for attending members. 115 seats were set - II~ for the annual luncheon meeting of the Division and approximately 175 members showed un. Since the hotel management would not serve more than the 115 it meant that 60 members were forced to eat elsewhere. This created hard feelings with some members. How- ever, officials of the Division were not able to obtain in advance any indication of this overflow crowd, but are suggesting to the New York Office that some means other than ticket sales be adopted to obtain an estimate of Division luncheon and dinner attendance. Members could be circularized prior to he meeting or they could be checked when registering as to the events they expect to attend. Under the inspiring leadership of Cadwallader Evans, Jr., Chairman, the Coal Division had a phenomenal growth during the year. Reporting at the luncheon meeting, Newel1 Alford stated that approximately 190 new members had been obtained. A few more years of continuing increase at this rate will make the Coal Division one of the largest Divisions in the Institute.

Jan 1, 1944

By E. A. Holbrook

LOCAL yearly taxes levied on bituminous coal lands in Pennsylvania have become a cost of first importance to the coal industry of the State. In Pennsylvania there is no State tax on real estate, but local taxation of real estate furnishes the greater part of the revenue necessary for the small governmental unit, as counties, townships, boroughs, and local school, road, and poor districts. Coal in place in the ground, whether or not title thereto has been severed from ownership of the surface, is assessed as real estate and on its supposed sale or market value. There are eight classes of counties in Pennsylvania, based on population; in populous counties of the first, second and third class, assessments are made by a county board appointed by the county commissioners and are fairly uniform throughout the county. In counties of the fourth to the eighth classes inclusive, property assessments are made by property assessors elected by and for each township within a county. In these counties the board of county commissioners acts as a board of equalization and review to hear appeals. In most counties, therefore, where there is a large unmined reserve of coal, assessments on that coal vary for each township, irrespective of the fact that the coal bed is continuous under many townships.

Jan 1, 1933

By AIME AIME

NATURE was in a smiling mood on December 18, 1883. On that day, Chester Alan Fulton, the sixty-first President of the American Institute of Mining and Metallurgical Engineers, was born, and she endowed him with every good quality within her reach - looks, physique, intelligence, and character. Brought up in the valley of the Hudson River, with the mighty Palisades which make it the "Rhine of America," he has lived up to his early promise - as a man, as an engineer and as a friend.

Jan 1, 1943

Arthur Jarman, Sydney, New South Wales, Australia (communication to the Secretary*):—All designs for modern metallurgical and chemical laboratories should provide each student's desk with a hood or cupboard for the removal of fumes, but I doubt the advisability of placing air-baths and similar apparatus close to the hot plate. It seems to me that unless the draft be exceptionally strong the fumes from ordinary wet assay work will corrode the iron-work of the fittings, in which case the baths would have to be removed to a general desk in order to lighten the work of the laboratory attendant. Since the laboratory described by Mr. White has been in use for two years, I should like to ask if any inconvenience has resulted from this corrosion. If not, it is certainly an important improvement to have the air-baths and similar apparatus placed on the student's desk. The hoods described by Mr. White are supplied with a good draft by means of a fan, which gives them a great advantage

Jan 1, 1905

THE research and policy committee of the Committee for Economic Development, a non-profit research organization composed of leaders in industry and the professions, including such prominent figures as Dwight D. Eisenhower, Paul G. Hoffman, and Charles E. Wilson, recently published a report entitled "How to Raise Real Wages." Since its founding in 1942 the CED has initiated many objective studies on matters of national economic policy, and has gained a fair measure of prestige from its activities. The CED's latest report cites the more than three- fold rise in real wages in the United States in the past 50 years and attributes the accompanying improvement in the standard of living to the great in- crease in production per man hour. The report states that in order for production to continue rising in the future with the attendant increase in real wages four basic conditions must be manifest: (1) better methods, (2) more capital, (3) better training of workers, and (4) better management. The report cautions that although prospects for increases in output per man hour are good "it is desirable that steps be taken to encourage such a rise."

Jan 8, 1950

By Fred J. Miller

FRED J. MILLER was born in Ohio, in 1857. He had a common and high school education, supplemented by personal study and special instruction. After serving a 4-year apprenticeship and working in various capacities in machine shops, he became a contributor to mechanical journals and finally a member of the editorial staff of The American Machinist, where he remained for twenty years, the last ten years as editor-in-chief of the magazine, and vice-president of the publishing company. On retiring from journalism, he was for nine years general manager of a group of typewriter factories, and was then commissioned Major of Ordnance in the U. S. Army, being stationed during most of his service at Rock Island Arsenal, where he organized the Civilian Service Division of the Arsenal. He is now a member of the Technical Advisory Committee of the War Claims Board at Washington. Major Miller became a member of the American Society of Mechanical Engineers in 1890, and has always taken an active interest in its affairs, having served on a number of important committees, and as a member of Council from 1904 to 1907, inclusive. He was elected President in December, 1919.

Jan 1, 1920

By AIME AIME

On Nov. 11, 1909, M. Alexandre Pourcel, of Paris, France, upon the proposal of a large number of distinguished members, and the unanimous recommendation of the Council, was elected by the Board of Directors an Honorary Member of the Institute. M. Pourcel has devoted forty-three years to the metallurgy of iron and steel ; and the work which he did between thirty and forty years ago constitutes an important part of the founda¬tion of the practice of to-day. Among his striking contribu¬tions are : (1) his perfection, in 1869, of the manufacture of high-grade ferro-manganese in a carbon-lined open-hearth furnace, instead of the costly crucibles previously used; (2) his discovery, in 1874, of the method of making solid steel cast¬ings; (3) his manufacture, in 1875, of ferro-manganese and silico-spiegel in the blast-furnace; and (4) his anticipation, in 1875, of modern American blast-furnace practice, by the pro¬duction, in a very small furnace, of Bessemer pig containing 2.5 per cent. of silicon, from a burden yielding only 46 per cent. of iron, and with a consumption, per ton of pig, of only 1,8401b. of coke, containing 15 per cent. of ash. These brilliant pioneer achievements, together with his contributions to cur¬rent technical literature, won for him the Bessemer gold medal of the Iron and Steel Institute ; the great" medal of honor," which is the highest award of the French Society of Mineral Industry, and other gold medals, as well as the distinction of honorary membership of the Comité des Forges de France, which was conferred upon him in 1891. In recent years, M. Pourcel has been instrumental, as consulting engineer of the Société de Commentry-Fourchambault, at Decazeville, France, in an extraordinary development of the manufacture of special steels. The Invar plant, of this company, is said to make a greater variety of such steels (includ-

Dec 1, 1909

By MORTON WEBB

Discussion of the paper of Max Boehmer, presented at the Pittsburg meeting, March, 1910, and printed in Bulletin. No. 38, February, 1910, pp. 119 to 122. W. MORTON WEBB, Germiston, Transvaal, South Africa (communication to the Secretary*):-The experience of Mr. Boehmer in the Leadville district and his reputation as an engineer assure the interest of anything he may write on the ore-bodies of that district; and all engineers who have operated in Leadville will agree that the theory of the origin of the Leadville deposits, as given by Mr. Emmons in his famous monograph, does not adequately explain the genesis of all the deposits. The solution of the problem does not, however, appear to be quite so simple as Mr. Boehmer would make it; and the advance pamphlet issued by the U. S. Geological Survey, pending the completion of the main report, shows that there is still much ground for controversy. No doubt the later eruptives had a greater influence on the deposition of the ore-bodies than was thought at the time of the first investigation by the Survey; but it has always appeared to me that the influence exerted by these dikes was more in the nature of a physical than a chemical one. The weight of evidence in recent years is mostly in the direction of ascension rather than lateral secretion; and one of the strongest evidences is the fact that most of the ore-bodies lie under one of the comparatively impervious layers which help to make up the structure of these hills. On Iron hill I have found a very persistent white porphyry sheet, split off from the overlying porphyry and lying from 30 to 60 ft. below the main white porphyry and blue limestone contact. This sheet varies from a few to 50 ft. in thickness, and where found adds another "contact" to that region ; some of the largest ore-bodies on Iron hill lie immediately under this sheet. Above this is the main white porphyry and * Received Mar. 3, 1910.

Feb 1, 1911