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By Walter Bradley

MINING by hydraulic process of the important gold-bearing gravels of the Sacramento Valley in the basins of the Yuba, Bear and American rivers began in 1853, and continued at an ever-increasing rate for 30 years. In its most active days it reached an annual production of $15,000,000, and averaged $10,000,000 per year over the 30 years. During that period no provisions were made to prevent the debris from being dis-charged into the water courses, and ultimately large quantities of silt, sand and gravel were washed down to the lower valleys; filling channels, causing overflow of agricultural lands and difficulty in maintaining navigable depths in the Sacramento River. Agitation and suits filed because of these damages finally resulted in the injunction decision of Judge L. B. Sawyer,1 in the U.S. Circuit Court, Jan. 23, 1884, which closed down practically all hydraulic mining operations not having means to restrain their debris. In 1893 (approved March 1, 1893), Congress passed the act introduced by Representative Anthony Caminetti, of California, creating the California Debris Com-mission, composed of three officers assigned from the Engineer Corps of the U.S. Army, and since that time it has been legal and possible within the drainage systems of Sacramento and San Joaquin rivers to conduct hydraulic mining of gold-bearing gravels behind dams built under this commission's permit and supervision. In the watersheds of the Trinity and Klamath rivers, which flow directly to the Pacific Ocean and do not affect navigation or agriculture, operating permits from the California Debris Commission are not required. There is a measure of restriction there, however,. through what is known as the Trinity and Klamath River Fish and Game Dis-trict. Chap. 215, Stat. 1931, in order to secure relatively clear water for the fishing season, provides that between July 15 and October 15 each year there must not be discharged into these rivers debris that will cause a turbidity greater than a content of 50 parts per million in the

Jan 1, 1936

By Richard E. Chism

Is my paper on Mexican weights and measures, presented at the Bethlehem meeting, I gave a formula for the reduction of Mexican ounces per carga to American ounces per ton, which may prove misleading. I wish therefore to substitute the following rule: To reduce Mexican ounces per carga of 300 Mexican pounds to Troy ounces per ton of 2000 pounds avoirdupois, multiply the number of ounces per carga by 6.078. Or, to reduce Troy ounces per ton of 2000 pounds avoirdupois to Mexican ounces per carga of 300 Mexican pounds, multiply the number of Troy ounces per ton by 0.165.

Jan 1, 1887

By Michel David

One of the most important questions that arises in ore estimation can be stated as follows: What is the error when one extends the grade of a sample to a certain volume? The theory of regionalized variables, with the concept of extension variance, provides a response to that crucial question for any kind of sample extended to any volume. For the usual "extensions" encountered in current mining practice, some simple results can be derived from that theory which was initiated by Dr. G. Matheron. These results have been applied to a stratiform lead-zinc deposit for which several estimations of grade, tonnage and related precision have been made for a series of grid sizes such as might be used in a progressive exploration program.

Jan 1, 1969

By Edward H. Robie

In late November and early December a considerable portion of our time was devoted to obtaining a business manager for Institute headquarters. The advisability of creating such a position was suggested in 1949 in the report of the Johnson committee. In that year, however, the Institute had a deficit of $72,000 so every effort was made to minimize expense. At that time most of the duties that normally would be assumed by a business manager were given to Newell Appleton who became office manager, convention manager, purchasing agent, and assistant to the secretary. So many responsibilities were his that he could not devote the necessary time to all of the many things that needed attention. H. H. Vasoll, representing a firm that made a study of Institute head office procedures early last fall, made a recommendation that "a business manager and controller from outside the present organization" be obtained, who would supervise the work of accounting, addressograph, purchasing, book and journal orders, filing, and mailing depts. He further recommended that Mr. Appleton be made administrative secretary, in which position he would act as head of an "Institute Activities Dept." He would devote his time to convention planning, meeting arrangements, travel accommodations, membership control and promotion, and public relations, and would assist the Secretary on special problems. Thus, Mr. Appleton retains some of his former responsibilities and will take more of the load off our shoulders in the conduct of affairs at Institute headquarters. The rest of his former work will be in the province of the newly created "Business Office Dept." Peter J. Apol is the man finally selected for the post of business manager. He is a young man of 32, a native Michigander and a graduate of the University of Michigan where he received a B.S. degree in business administration in 1940. He then spent three years in the Navy and has the rank of Lieutenant in the U. S. Naval Reserve. Three more years were spent in the U. S. Maritime Service as chief purser, and another year as chief paymaster for the Pope & Talbot Steamship Co. The past four years have been spent as head of the Greenland Construction Co., Greenland, N. H., chiefly engaged in building construction. Mr. Apol will endeavor to increase the efficiency of Institute headquarters operations and remove all possible causes for complaints of individual members. He will coordinate as seems advisable the work of various departments and install such modern business office machinery as seems applicable to our needs.

Jan 1, 1952

Albert SaUveur, Cambridge, Mass. (communication to the Secretary*):—On close examination I think it will be found that the evidence by which Mr. Corson claims to have shown the inaccuracy of a statement I made a few years ago, is far from convincing. This statement is: "Hot work as such has no influence upon the structure of the metal. Indirectly, however, by retarding crystallization until a lower temperature is reached, it may influence its structure most decidedly ; but the same results could be accomplished by heat treatment alone, i.e., by re-heating the unworked metal to the temperature from which the worked piece was allowed to cool undisturbedly." The Melallographist, vol. ii., p. 267 (under the head of "Changes of Structure Brought About by Work"). Of the two pieces of steel tested by Mr. Corson, one was worked and finished at a a cherry-red" and the other reheated to a cherry-red, and the assumption was made that in both cases the temperature was about 715' C., although no pyrometric device was used to record it. The possibility of considerable difference in temperature alone is so great as to invalidate Mr. Corson's inferences. The apparent temperature,

Jan 1, 1907

By James H. Bechtold

The yield strength of annealed tungsten was found to have a strain rate exponent 12 times as great as that of low carbon steel. The effects of temperature and strain rate could be correlated through the Zener-Hollomon parameter with a heat of activation associated with yielding of 32,000 cal per g-atom. This heat of activation is independent of strain although both the temperature and strain rate dependence of the yield strength vary with strain. MOST metals have mechanical properties that are relatively insensitive to strain rate, especially at temperatures below that at which creep is important. In iron and molybdenum," however, relatively large strain rate effects are observed in the temperature range where the rapid increase in yield strength occurs which leads to the ductile to brittle transition. In this temperature range Zener and Hollomon' have suggested that the effects of strain rate and temperature T on the yield strength could be correlated through a single parameter, P, in the following manner where Q is a heat of activation characteristic of the metal and associated with some unspecified relaxation process. They also observed that if the temperature is restricted to a relatively narrow range— below room temperature for steel—that the logarithm of the yield strength could be expressed as a linear function of the logarithm of P. From this relation the logarithm of stress should be a linear function of the logarithm of the strain rate at constant temperature: where r will be referred to herein as the strain rate exponent. At a constant strain rate the logarithm of stress should be a linear function of l/T, ay(e = C) ~ eT [4] where q = Qr [5] and is referred to herein as the temperature exponent. These equations have been found to relate the effects of temperature and strain rate on the yield strength of molybdenum in the temperature range wherein the ductile to brittle transition occurs, —75° to +150°C.2 Bechtold and Shewmon3 have shown recently that the ductile to brittle transition in annealed tungsten occurs in the temperature range +150° to +350°C. In this temperature range the yield strength in-

Jan 1, 1957

By K. E. Manchester, A. H. Clark

Hall measurements have been made on three groups of silicon samples, which were implanted with boron, aluininunz, and phosphorus ions. Boron and phosphorus implants show essentially bulk properties when annealed under previously determined conditions, i.e., 15 min at 80O°C for boron and 10 mirz at 600°C for phosphorus. Bulk properties were also observed in alu?rrilzum-implanted samples when ion concentrations were below 1015 cm-'; however, strange low- terrzperalure behavior and a falloff in cavrier concenlralion was observed for sarnples with ion concenlration abozle loL5 ern-'. This can be attributed to solid-solubility effects since the average bulk concentration f0.r the sample exhibiting bulk properties was below the reported solubility limit for aluminum, while the other samples were above the limit. A detailed study of the annealirzg process indicates that mobilities reach bulk c~alues in phosphorus implants at 250DC, in alutninurn ivnplanls a1 500°C, and in boron implants at 700°C. A simple rnodel has been proposed to fit the annealing data. THE technique of semiconductor doping by direct injection of energetic ions is being actively investigated at this Center. Previously published results from this laboratory have been concerned with the investigation of implanted profiles in silicon and the electrical properties of the resultant p-n structures.1'2 Diode properties have been reported for junctions produced by implantation of boron ions and aluminum ions in n-type silicon and phosphorus ions in p-type silicon. Reverse current characteristics, as well as electron diffraction data, have indicated that the damage to the structure produced by the energetic ions during the stopping process can be minimized by a gentle anneal. The time-temperature conditions for this process have been determined by sheet resistivity studies.3 Electrical profiles of implanted phosphorus ions which have been determined by a differential sheet conductivity technique are based on the assumption that the carrier mobilities and activation energies for ionization are the same as in bulk silicon. These assumptions have been substantiated experimentally by measurement of Hall constants and resistivities of these implanted structures and the results are presented herein. After establishing the bulk property equivalence of the annealed layers, a more detailed examination of the annealing process was undertaken. The sheet resistivity technique initially used to determine anneal conditions has been broadened to include Hall constants and mobility behavior with anneal conditions. PROCEDURE The three groups of samples prepared for Hall measurements were implanted with mass-separated beams of boron, aluminum, and phosphorus ions. Ion concentrations are equivalent surface concentration and they have been determined from beam current measurements during implantation. Implant conditions for the samples are shown in Table I. In all cases, the samples had previously been angle-lapped on one edge and the junction delineated with an HF-copper sulfate solution. The surfaces of the implanted regions of the samples were exposed to the delineating solution and in the case of the "n"-type phosphorus-implanted areas it was later discovered that a finite amount of surface could be etched by this solution. This is discussed in the section on results. The implanted samples were ultrasonically cut into the conventional six-probe configuration shown in Fig. l.* In the annealing studies, for which the meas- urements were taken at room temperature, the sample holder was a Bakelite jig incorporating tungsten mechanical probes. The other measurements were taken using a conventional liquid-nitrogen cryostat, in which the temperature could be varied from 77" to about 400°K. For these measurements, 10-mil aluminum dots were evaporated onto the samples and alloyed with the silicon at 530°C for 15 min. The samples were then mounted in flat-packs, and gold wires were bonded to the aluminum dots. The electrical measurements were made with either a Leeds & Northrup K-5 Potentiometer, a Keithley 147 Nanovolt Null Detector, or a Keithley 601 Electrometer. No external bias was applied to the substrate. There is an inherent self-biasing arrangement at one or the other of the current contacts (depending upon the polarity), and this suffices to limit the current flow to the implanted layer. The magnetic field was generated by an A. D. Little electromagnet. Except for occasional checks of linearity of the Hall voltage with

Jan 1, 1969

By T. L. Johnston

MUCH has been said and written about deep mine shafts and deep drill holes as man in his search for mineral wealth digs deeper into the earth's crust. Each year some new extra depth is heralded as a record, but with unlimited possibilities of going still deeper. In contrast to "digging deep," "mining high" is limited by the height of the mountains (Mt. Everest being the maximum with its 29,000-ft. elevation) and also by the extent of human endurance. An ex- ample of what might be called near- stratosphere mining in what is probably the highest mine worked by compressed air in the world is seen in a recent project in the Andes mountains of southwestern Bolivia.

Jan 1, 1939

By W. G. Jewitt

YELLOWKNIFE, the most northerly Canadian gold mining district, is once more in the throes of a boom. Touched off by spectacular and well-publicized diamond-drilling results on the property of Giant Yellowknife Gold Mines, Ltd., mining companies and the general public are competing for mining claims and for the shares of companies owning mining claims in the area, with little regard for values. Such a stock-market boom has various unfortunate consequences but undoubtedly one beneficial result is that considerable amounts of money are made available for serious development. The Yellowknife mining area lies on the north shore of Great Slave Lake, in the Northwest Territories, at a latitude of approximately 62°30' north. The topography is a low-relief phase of that usual in the Canadian Laurentian shield. Roughly, one third of the surface is lake-covered, one third muskeg or overburden, and one third is bare

Jan 1, 1944

By D. S. Bloom

RECENTLY a report has been published on an investigation of the MO-RU system by E. Raub.' In this report it is stated that below approximately 1200°C the system consists of two terminal solid-solution phases and the intervening two-phase field; at 1200°C and above, an intermetallic compound labeled Mo,Ru, makes an appearance. Along with some other little known systems in which it was considered possible for a u phase to form, the Mo-Ru system had been under investigation in this laboratory. Since molybdenum and ruthenium have very high melting points and also since ruthenium is expensive, the investigation was confined to X-ray diffraction by sintered powder compacts. The compositions which were studied were (in atomic percentages): 75 Mo-25 Ru, 67 Mo-33 Ru, 50 Mo-50 Ru, and 25 Mo-75 Ru. All compacts were made from the pure powders, and no chemical analyses were attempted. Each compact weighed about 5 g. All annealing was done in evacuated Vycor capsules, and even though the capsules completely collapsed at 1250°C, they still admitted no air. The results of this investigation in general corroborate the work of Raub. Up to 1150°C the two terminal solutions and the intervening two-phase field were found, and at 1200°C and above an intermetallic compound was found. However, the composition limits of the compound were estimated to lie close to 70 atomic pct Mo rather than 62.5 atomic pct Mo as Raub had reported. At least the X-ray diffraction results indicated that the 75 atomic pct Mo specimen consisted of the molybdenum solid solution plus the compound, while the 67 atomic pct Mo specimen consisted of the ruthenium solid solution plus the compound and the equiatomic composition contained only very little of the compound. The most interesting observation, however, was that the diffraction pattern of the compound was similar to that of the well known u phases, except that unusually large lattice constants were indicated. The d-values, or interplanar spacings, of the diffraction lines (as produced by filtered copper KCX radiation) of the compound are given in Table I, as determined from specimens annealed at 1250°C for 9 hr and then quenched in water. Also shown are the lines of the Mn-Mo u phase as given by Decker, Waterstrat, and Kasper,' the lines of the Fe-Mo a as given by Goldschmidt," and the lines of the Mo-Ru phase multiplied by constants in order to make comparison with the Mn-Mo and Fe-Mo patterns easier. These results indicate that the compound in the Mo-Ru system is apparently isomorphous with the other o- compounds. The rather large lattice constants of the Mo-Ru a phase are acceptable in view of the comparatively large size of the constituent atoms. The data in Table I for the Mo-Ru compound check quite well with those given by Raub, not shown here, though there are some discrepancies between the two sets of data in the estimated intensities of a few lines. Although very little is known at present about this u phase, there are some things which may be pointed out, mainly in comparison with other better known u phases. Even though molybdenum and ruthenium are in the same columns in the Table of Elements as chromium and iron, respectively, the Mo-Ru u phase contains much more molybdenum than ruthenium, while the Cr-Fe u phase centers around or very nearly around the equiatomic composition; furthermore, the Mo-Ru u is stable only above approximately 1200°C, but the Cr-Fe u is stable only below about 825 °C. With respect to its being unstable below 1200°C, the Mo-Ru u is similar to the other binary molybdenum u phases in the Co-Mo and Fe-Mo systems. Similar to the latter two systems, the Mo-Ru u apparently exists over a rather narrow composition range, whereas the Cr-Fe u at lower temperatures is stable over a much wider composition range. The Mo-Ru u thus is closer to the other molybdenum u phases than to the Cr-Fe cr phase. The most striking feature of the Mo-Ru u phase, however, is the absence of any of the transition elements of the First Long Period.

Jan 1, 1956

By Harlowe Hardinge

AN extensive recent trip throughout the mining districts of the Southwest, Central West, an Northwest,' reveals a numbes of interesting conditions that have influenced operators, in both large and small mills, to modify their flow sheets insofar as they pertain to crushing and grinding. The changes made and planned for the future should be of interest. It is interesting to note when traveling through the country, how ideas change and practice is modified, and it is rather amusing to see how milling methods seem to run, more or less, in cycles. New ideas and developments are brought about which run through the industry and are taken up by many of the best and most well informed operators. Some of them will change, sooner or later, back to their old practice; for, like everything .else, what will work well in one place will not necessarily be suited to another. On the other hand, it is often difficult to establish. other practices known to be of value, owing to the natural resistance to make a change, but on the whole, the western mill men seem to be more alive to possible benefits of various modifications than any other engineers with whom I have come in contact in all parts of the world. Mill men in other parts of the world always keep in con- tact with what is being done in the western part of the United States, but it does not necessarily follow that those in the western part of the United States are always right. Some of these changes that have been made and afterward abandoned will be referred to later.

Jan 1, 1929

By Benjamin C. Craft

Oil and gas development in Louisiana during 1935 brought this state at the close of the year up to fourth place in the nation as a producing area. A review of development in North Louisiana centers around Rodessa, the most important reserve discovered in this area in many years. While the producing limits have not been defined, this discovery is one of the major developments of the year. New gas fields were discovered in Lincoln, De Soto and Bossier parishes. The Lincoln Parish discovery, completed flowing a highly saturated gas from the Glen Rose, further indicates the importance of deep-seated prospects in the interior salt-dome area. Minor extensions were made at Sligo and Pine Island. During the year, 126 oil wells and 103 gas wells were completed in North Louisiana as compared with 144 oil wells and 68 gas wells during 1934. The North Louisiana oil production was 9,617,405 bbl. as com-pared with 9,274,050 bbl. during 1934, an increase of 343,355 bbl., while the gas production increased 18 billion cu. ft. in 1935 over its 1934 figure. The Louisiana Department of Conservation gage of Nov. 1, 1935, shows an open-flow capacity of 4,563,725,000 cu. ft. per day from 941 wells in the Monroe field and 682,770,000 cu. ft. from 159 wells in the Rich-land field. A great deal of leasing continues in North Louisiana as a result of the Lincoln Parish discovery and development in the Rodessa field, especially in Bossier, De Soto, Winn, Lincoln, Bienville, Webster, Ouachita and Richland parishes. South Louisiana's position as an area of important reserves was further proved during the past year. Increased drilling resulted in the discovery of seven new fields: Lafitte, Garden Island Bay, Tepetate, Bunkie, St. Martinsville, Jeanerette and Big Lake. New sands or producing horizons proved productive in 15 of the proven fields. The total oil production for South Louisiana during 1935 was 40,731,-056 bbl. as compared with 23,255,437 bbl. during 1934. There were 222 oil and gas wells completed in South Louisiana during 1935 as compared with 214 oil wells during the previous period. Drilling during

Jan 1, 1936

By R. J. Hopkins, L. B. Haney

On the basis of limited experimental work conducted at the Port Pirie smelter, it would appear that, by increasing the specific surface of sinter, and possibly that of coke as well, a marked increase in the rate and degree of sinter reduction in the furnace shaft can be achieved. Fusion-point tests have shown that this increased reduction means a much higher sinter fusion point and narrower plastic zone, while the more efficient utilization of coke in the furnace is inherent in the intensification of reduction by the provision of a more reactive sinter surface. Investigations aimed at increasing the ability to operate the blast furnace with a higher lead tenor of sinter reducing fuel cost proportionately, and at eliminating the loss in reduction potential in coke entering the furnace, as shown by the presence of appreciable proportions of CO in the top gases, are reported. Several lines for future investigations that could result in improved smelting methods are proposed. A SOMEWHAT informal presentation of ideas on lead blast-furnace smelting will be given in this paper. These ideas have been developed during observations of furnace behavior at Port Pirie and earlier at Mt. Isa, and have been guided by the results of laboratory experiments at Port Pirie. The authors do not intend to propound any particularly new theories, but present their ideas as a basis for discussion which may help toward a better understanding and improved control of blast-furnace operation. Performance variations of considerable magnitude occur from time to time at most lead blast-furnace plants. While Port Pirie is fortunate in having a very regular supply of high grade concentrates, it is no exception in this respect. Such irregularities are of considerable economic importance and they constitute a challenge to present-day metallurgists in their efforts to obtain an ever greater degree of control over furnace operation. In operating as Port Pirie does with a relatively high lead charge, it has been recognized for a long time that shaft conditions are ,of the greatest importance. A practical, or engineering, attack on the problem of accretions consisted of changes in furnace design, e.g., by widening the shaft to 10 ft above the bottom row of tuyeres, and by the provision of curved ends and vertical walls.' That this attack has had a great measure of success is shown by the fact that barring down of these wide furnaces is rarely necessary, shaft conditions have greatly improved, and sensitivity to charge variations has been markedly reduced. These modifications, followed by some metallurgical changes (chiefly the incorporation of pig iron into the furnace charge in 1948), have brought furnace operation to a point where some variables which were previously masked can now be studied. Accordingly, over different periods of time during the last five years, such variables as could be given numerical values have been recorded and subjected to statistical examination. The objectives of this work were: 1—to reveal the true importance of the different variables and 2—to show the proportion of total furnace variation which is unexplained and therefore referable to causes not measured at present? e.g., shaft accretions, sinter structure, coke structure, and others. Statistical Study of Variables In this work factors relating to furnace speed and lead reduction have been examined: 1—slag com-

Jan 1, 1955

By Thomas T. Read

EVERYONE engaged in the teaching of mining engineering will, I suppose, agree that the most difficult subject to teach is "Mining Methods." One primary difficulty is that the students taking the course have either had no previous experience in mining, or else they have had; either seeming to be somewhat of a drawback. The students who are unfamiliar with mines find it difficult to visualize underground conditions, as described and illustrated with sketches and maps, while those who have had underground experience seem to 'find it difficult to visualize anything much different from that which they have already seen. This reminds one of the remark about the Presbyterian doctrine of predestination, to the effect that "you are damned ,if you do; and damned if you don't."

Jan 1, 1930

By J. A. B. Forster

W. G. WOOLF*—The paper has a wealth of data that take careful, detailed study. As has been indicated the highlights can be only touched in the paper. The design and the arrangement of the rabble teeth as well as some of the other details of operation show a very careful study and a scientific approach to the problem which in most plants using hearth roasters are matters of trial and error with empirical conclusions and, perhaps too often, just arbitrary supervisory preferences which may be erroneous. Here the problem has been approached from a scientific angle which think well merits careful study. The ability to treat the tonnages they get through these furnaces think is made easier by reason of the high sulphide sulphur in the resulting calcines which the balance of the plant—the leaching and so on—can cope with. As indicated by Mr. Weldon in his dis- cussion earlier this morning, in most zinc plants an attempt is made to have as low a sulphide sulphur content in the roaster calcine as possible. But in the operation of the Risdon plants, they are able to cope with sulphide sulphur content up to 5 pct which is far beyond the amount of sulphide sulphur that can be handled elsewhere. I think the autogenous roasting is made easier because driving out the last percentages of sulphide sulphur brings on the necessity for extraneous heat, and that is further exemplified because even at Risdon the author shows the desirability of using some oil to better the operation, particularly for uniformity of roasting results and to obtain more regularity of furnace operation. A. A. CENTER*—Regarding the hard crusts in the beds of the furnace and autogenous roasting, the paper speaks of the former being due, at least to a considerable extent, to lead sulphide in the crusts. I wonder if the author has considered the hard crusts as being due in large part to zinc sulphate. While I was developing large zinc operations we ran into hard crusts which had to be dug up. I took several lumps which were so hard they showed the marks of the rabble teeth very plainly and kept them in my office for some weeks. A visitor came along one day, and as he was having similar troubles, I told him what we were doing about ours. I started to pick up one of these lumps and to my amazement the thing crumbled in my hands whereas originally it had been so hard it wore the rabbles down very rapidly in the furnace. I sent the sample to the laboratory and found that it analyzed very high in water-soluble zinc and sulphate-sulphur. The crumbling of the lumps was evidently due to the anhydrous zinc sulphate gradually taking on moisture from the air and forming crystalline zinc sulphate seven parts water. The increase in volume would, of course, result in disintegration of the lumps. As to getting a high tonnage in the autogenous roast, that is partly because of finishing at about 5 pct sulphide sulphur. It is a real job to get down to, say, ½ pct sulphide sulphur, which is what is usually desired, and still put through a good tonnage.

Jan 1, 1950

The engineering personnel shortage, present and impending, so well brought out in the article in Mining Engineering in the August, 1951 number, both in the editorial lead and the article by William B. Plank and Henry J. Petrie, has left untapped and has ignored a potential source of supply that would fill the need ably and with complete satisfaction. This source is comprised of the women engineers- and geologists, both presently, trained and able to handle work at all levels, and the many who would make splendid engineers and geologists if they could hope for even a modest taste of the square deal that should be theirs, but, as we all know, is not. I write from experience. It is not pleasant or sensible to have to urge borderline cases among men students to consider engineering and geology as careers to fill the need, when I have far more able, interested and suited young women students whom I must divert into other channels. It does not make sense to scrape the bottom and sides of the barrel to induce potentially second or third rate male engineers and geologists to enter the profession when we have superior material among the women, eager to do good work in these fields. It does not make sense for these men to become second or third rate in these fields when they might be first rate salesmen, musicians, advertising copywriters or policemen. Nor does it make any more sense to force potentially first rate female geologists and engineers to become second or third rate and very frustrated typists, kindergarten teachers, dress sales-women or clerks. At this point I am willing to admit that where superstitious -miners object to women in underground workings, men are available for the jobs. Moreover, it is not necessary for women to be sent into the most difficult country, if there is reluctance on either side of the contract. There may be fewer of them eager for the roughest assignments, in proportion to the men, but women are so accustomed to discrimination far more complete than that against any racial or religious group, that a reasonably tough assignment would seem like a heaven-descended joy. In my own experience, I have found that my girl students majoring in geology, could keep up with me in the field in the roughest terrain, but. the men, all but the best students and the most physically fit young men, complained that they could not keep up with me and that I always "walked their-legs off. The women, a few men and I always returned with bags heavy with well chosen specimens and proper notes. Most of the men carried no specimens and-but poor scraps of notes on loose bits of paper. Yet the men were urged to prepare for a career in engineering or geology if their examination marks were reasonably good. When we find that we still have a shortage of engineers and geologists, after putting all the qualified women to work, then we may begin to worry. Until then, we are simply fooling ourselves as we wander in, a forest of outmoded tradition and emotional habit reactions. MARY W. GARRETSON ASSOC. MEMBER, AIME SCARSDALE, N. Y.

Jan 1, 1952

By V. H. Wilhelm

WITH rapidly diminishing oil reserves: a great percentage of which are uneconomical at present prices, some of the existing methods of development and production will have to undergo radical re- visions to meet the changes continually taking place in the petroleum industry. Imagination in an engineer is a great asset. The fancy of today is found to be the realization of tomorrow, and with this thought in mind, there is here presented a more or less imaginative picture which, to my mind, has a meritorious basis. Directed drilling has reached a stage of accuracy sufficient to allow the prediction that this art will be used in the future development of oil structures, especially those \\,it11 thin sand bodies 'and steep dips. Directional drilling in a number of fields in California has gratifying results. Wells which practically laid pipe lines through the oil sands have enjoyed a greater drainage radius with a consequent greater initial and cumulative production. In one field where the vertical thickness of sands was approximately 550 ft., wells drifting at an angle as great as 55 deg. fro111 vertical had over 1100 ft. of perforated pipe in contact with these sands. These wells were, and are, remarkable for their great initial pro-

Jan 1, 1936

By AIME AIME

READERS of a technical paper, or the audience if the paper is presented orally, judge the paper on several counts. The September 1940 issue of MINING AND METALLURGY contained an excellent short article by S. Marion Tucker en- titled "Are You Going to Present a Paper," which considered the general subject of presentation. In it Dr. Tucker referred to the large number of poorly prepared and badly delivered papers that are presented annually before the large number of technical and other societies that meet regularly, and he stressed the point that good delivery, length of paper, content, and composition are of great importance. All of Dr. Tucker's points were well taken; however, good illustrations are equally important in explaining certain phases of some papers.

Jan 1, 1941

By J. W. JESSUH

TO certain people the name of Northern Rhodesia brings only a vague recollection of a distant country somewhere in Africa; to others, it means a big game territory and the opportunity for excellent shooting; to some, a land of sunshine and peace; but to mining men the name signifies the land where the latest discoveries of copper ore are astonishing the mining world and bid fair, in a few years, to make Northern Rhodesia one of the largest copper- producing countries. There is a fascination about this part of the globe that is somewhat similar to southern California, and at the same time there is that feeling of mystery peculiar to a tropical climate. Perhaps it is the isolation, the fear of wild animals, or the influence of an undefinable something which cannot be expressed.

Jan 1, 1931

By F. N. Ward, E. H. Bailey

Camp and sample-site methods useful for determining about 0.5 to 16 ppm of mercury in soils and rocks have been devised to complement the analytical methods already widely used in geochemical prospecting. In the camp-site procedure the sample solution is obtained by digesting the finely powdered sample with hot nine-molar sulfuric acid and bromine, the latter generated in place. The solution is buffered at a pH of 4 and the mercury is extracted into a relatively small volume of an organic solvent. Estimations are made by comparing the color of the mercuric dithizonate extracted from the sample with that extracted from a standard. In the sample-site method the mercury is volatilized as the iodide and the latter is dissolved in a buffer solution from which the mercury dithizonate is extracted as in the camp-site method. The estimation is made by a similar comparison with standards or by comparing the color of the mercuric dithizonate with artificial standards prepared from Orange II, an azo dye. Except for the establishment of standards, the time required by an experienced analyst seldom exceeds 10 min for a camp-site determination and 5 min for a sample-site determination. Camp-site determinations are useful for commodity studies and intensive exploration programs; sample-site determinations are applicable to extensive and reconnaissance-type geochemical prospecting programs. The results obtained on samples taken along traverses above known mercury ore deposits in the California Coast Range and western Nevada demonstrate the usefulness of both methods in geochemical prospecting. The increasing use of the mercury content of soils, rocks, plants, or water in geochemical prospecting emphasizes the need for analytical methods which are sensitive and at the same time require a minimum of readily available equipment. Sensitive methods based on the absorption of ultraviolet light by mercury vapor are common in the literature31 12. Although none of these methods have been used to analyze the large number of samples required in geochemical prospecting, they could be extremely useful except for the expensive instrumentation usually required to make the methods quantitative Also, such methods are perhaps too sensitive for field use, especially around areas of possible contamination. Other methods involve the distillation of mercury from a relatively large sample and subsequent collection of the vapors in nitric acid6. The mercury is then estimated by titration with a suitable reagent such as thiocyanate. These methods are not trace methods because the actual amount of mercury measured is often as great as 50 to 100 milligrams. Also, such methods are unsuitable for geochemical prospecting because of the amount of equipment necessary and the time required. Still other methods involve colorimetry, and the sensitive reaction between dithizone and mercury (11).. is the basis for a number of reports on the determination of mercury in biological materials 5,7. Moreover, by the judicious use of solvent extraction and suitable complexing agents, the dithiaone method can be made almost specific for mercury. However, none of the dithizone methods have yet been applied to the determination of mercury in soils and rocks. In most colorimetric methods he sample solution

Jan 1, 1961