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By R. W. Balluffi, B. H. Alexander

RELATIVE diffusion rates of copper and zinc in a brass have been measured in a vapor-solid type of couple with which the amounts of copper and zinc diffusing past inert Kirkendall markers can be obtained by means of a few simple experimental measurements. If inert markers are placed on the surface of copper which is then exposed to zinc vapor from a brass chips, the particles become buried due to outward diffusion of the copper, as shown in Fig. 1. A schematic diagram of such a couple after diffusion is shown in Fig. 2. Consideration of the diffusion flow of copper and zinc shows that the entire hatched area, including the cross-hatched area, is proportional to the amount of zinc diffused inward past the markers and that the smaller cross-hatched area is proportional to the amount of copper diffused outward past the markers. These areas are completely determined by the expansion of the couple, the depth of the buried particles below the surface, and the chemical composition at the specimen surface. As Darken1 has shown, the ratio of diffusivities of copper and zinc is then given by the ratio of these two areas. Polycrystalline copper and two copper single-crystals made by the Bridgman method were prepared in the form of 1.5 cm diam disks approximately 0.5 cm thick with faces plane and parallel. Tungsten particles approximately 0.001 cm in diam were bonded to the surface of each disk by heating 5 hr at 1060°C in vacuo. Each specimen was next

Jan 1, 1953

By E. S. Machlin

RECENTLY, there has been much activity in the field of nucleation of martensitic transformations.'- One of the problems in this field is the calculation of the rate of nucleation (number of plates nucleated per unit untransformed volume per unit time) in terms of observable parameters. Two such observable parameters are the fraction of the length of a straight line which corresponds to the portion of the total length of the line that lies in the martensitic phase and the number of plates intersected by this straight line per unit length of line. Because of the necessity of a valid answer to this problem, the following investigation was undertaken. Although this problem has been treated in the past, a derivation of the relation between the volume and linear fractions of martensite will be described to illustrate the method used in the succeeding analyses. It is assumed that the martensitic plates are in the form of a right circular cylinder having a small height relative to the radius of the base. The volume fraction of martensite is then: fr = lXNl,hjAl [1] where f, is the volume fraction of martensite, and Nij is the number of plates per unit total volume having the area Ai and the height hi. The linear fraction of martensite is obtained as follows. For the plates having the particular area A, and height h,, the fraction sin 0 dB* will have their cylinder axes between the angles 0 and 0 + d0 to the straight line along which the linear fraction of mar-

Jan 1, 1953

By Bernard E. Fernow

About eight years ago a comprehensive study of American timbers was begun in the U. S. Division of Forestry with a twofold object. On the one hand, it was desired to deternliiie the working-qualities of our numerous economically important timbers, and to furnish reliable standards of strength. 011 the other hand, it was intended to get a clearer insight into the properties and behavior of wood in general, with a view of establishing more rational methods in its use, and to furnish data for physical inspectioil which would permit an intelligent application of the standards of strength, and place upon a rational foundation the so-called " factor of safety," which is at present a mere baseless guess. The first object, namely, the establishment of standards for any given species, requires a very large series of tests, since Wood is an exceedingly variable substance, so much so that in the same tree a variation of 50 per cent. in strength may be found; hence the greater need of rational data of inspection. So far, the insufficient appropriations and facilities at our disposal have permitted us to establish really reliable standards for five species of southern conifers only. These have been deduced from nearly 20,000 tests. Besides these, 10,000 other tests have furnished indicatious regarding some two dozen other species. This work is now entirely abandoned, waiting for more prosperous times. The study of wood in general, however, can be carried on with smaller means, and has this year yielded not only very interesting, but highly important results, which will soon be published in detail. It is the purpose of this paper to make to the Institute the

Jan 1, 1899

By Paul Hett

The much-heralded Deep Ruth operation of Kennecott Copper Corp., at Ruth, Nev., is scheduled to become a producer by 1957. Inaugurated as a project in 1951, production was originally scheduled to start in 1953, but excessive water hindered shaft sinking. A revised schedule called for output by 1955, but again plans had to be changed. This time the change was to permit mining of an orebody that would have otherwise been lost because of block caving methods planned for the main deposit. The new ore is within the cave limits of the larger orebody, above the first production level. Ore will start coming from this new source in 1956, a year ahead of the principal operation. (See NEWS, page 344.) There is little doubt that current economic conditions and unforeseen expenditures for early shaft development will make the Deep Ruth a high-cost producer. Yet, some of the drawbacks of the Kennecott operation may be mitigated by the possibility that additional exploration will increase the already assured 25 million tons of 0.83 pet copper ore. While Kennecott is missing out on the current high copper market and is thus left with a potentially narrowed profit, the predicted demand for copper has created an optimistic feeling. Its development is certain to enlarge known U. S. copper reserves and significantly extend the life of Kennecott's Nevada operations.

Jan 4, 1955

By Rossiter W. Raymond

(Read at the Amenia Meeting, October, 1877.) THE term "pipe-vein" has recently been applied in this country to certain deposits of lead ore in magnesian limestone. The use of the term has been twofold. It has been revived as a term found in textbooks on mineral veins, with the implied or declared assertion that the ore-deposits thus named in this country are similar to those which have borne the title abroad. It has also been advanced as an appropriate name for a new class of deposits, even if such a class had not previously been recognized. In either case, the assumption is that pipe-veins form a group or class by themselves, and are not merely interior and subordinate features in larger deposits. The peculiar mining law of the United States, which regards " the vein," whatever that may be, as the basis of title, lends a special interest to these claims. But the object of this paper is rather to discuss the subject from the standpoint of geology and technical literature. I shall briefly answer two questions : (1) What are pipe-veins as described in technical literature? and (2) Is the name appropriate or necessary for a new class of deposits ? The term "pipe-ore," as applied, for instance, to irregular, cylin-

Jan 1, 1878

The Development of Research and Quality Control in the Modern Steel Plant. By Leo F. Rein-artz. (Metals Technology, April 1943) Blast Furnace and Raw Materials Essential Considerations in the Design of Blast Furnaces. By A. L. Foell. (,Metals Technology, December 1942) Results Obtained from Surveys of Gas at Furnace Tops. By James M. Stapleton. (Metals Technology, January 1943) Physical Aspects of the Dust Catcher, Gas Washer and Precipitator on No. 3 Furnace at Carrie. By C. P. Clingerman and C. J. FleiscH. (Metals Technology, January 1943) Slag Control by Introduction of Flux through Blast-furnace Tuyeres. By Carl G. Hogberg (Metals Technology, January 1943) The Electrical Conductivity of Molten Blast-furnace Slags. By A. E. MaRtin and GerRard Derge. (Metals Technology, August 1943) Some Physical Characteristics of By-product Coke for Blast Furnaces. By CEarles C. Russell and MichaeL Perch. (Metals Technology, December 19+2) Pyrometry at the Coke Oven. By Robert B. Sosman. (Metals Technology, December 1942) Calcination Rates and Sizing of Blast-furnace Flux. By T. L. Joseph, H. M. Beatty and Gust Ritsianes. (Metals Technology, December 1942) The Low-temperature Gaseous Reduction of a Magnetite. By M. C. Udy and C. H. Lorig. (Metals Technology, October 1942) Steelmaking Problems of Total Operation in Steelmaking. By William C. Marshall and Frank G. Norris. (Metals Technology, April 1943) Silicon-oxygen Equilibria in Liquid Iron, By C. A. ZapFFe and C. E. Sims. (Metals Technology, September 1942) Equilibria of Liquid Iron and Simple Basic and Acid Slags in a Rolating Induction Furnace. By C. R. Taylor and John Chipman. (Metals Technology, September 1942) Rapid Analysis of Oxygen in Molten Iron and Steel. By Gerhard DeRGe. (Metals Technology, January 1943) Silver Chloride as a Medium for Study of Ingot Structures. By Karl L. Fetters and Margaret Dienes. (Metals Technology, August 1943)

Jan 1, 1943

By Gary J. Brown

AMAX Coal Company, the nation's third largest coal producer operating in Indiana, Illinois and Wyoming, is a division of AMAX, INC., a United States based natural resources corporation that operates world wide. The operations in Wyoming (The Western Division) include Belle Ayr and Eagle Butte Mines. Belle Ayr Mine, located 18 miles south of Gillette, Wyoming, presently employs 440 people. It was started into production in 1973 and has been the largest producing coal mine in the United States since 1977. Final figures will show that the mine was again the largest in 1980 with production levels of approximately 16.1 million tons, total production of coal in the United States being in excess of 800 million tons during this last year. As one of the first commercial producers of sub-bituminous coal in the Powder River Basin, Belle Ayr has served as an example for the many other mines which have since been constructed in that region. The four coal storage silos are the first and most dominant features of the mine to be seen for miles across the Wyoming prairie. Each silo has the capacity to load a 110-car unit train in excess of 11,000 tons. All service facilities at the mine are under one roof. Included in the service building are off ices, warehousing, seven garage bays, and washhouse facilities for all employees. Preparation of coal for shipping at Belle Ayr consists only of crushing from pit-run size to 2 x 0-in. Primary crushing is done under the truck hoppers to 6-8-in. product size. Secondary crushing is performed in the two large crusher buildings. The smallest plant can produce at the rate of 2,500 tph, while the larger can produce

Jan 1, 1983

By Jan D. Miller

Under the name given to this column, I almost feel obliged to write about some aspect of grinding, but I have decided instead to comment on the future of chemical processing. In recent years, I have seen a tremendous interest in extractive metallurgy develop among undergraduate and graduate students at the University of Utah. For example, of the 12 graduating seniors this year, over half seem to prefer extractive metallurgy to physical metallurgy. In particular, they seem to be most interested in hydrometallurgy, or chemical processing, obtaining industrial exposure to the phenomena they study via part-time employment at the Kennecott Research Center and the USBM Metallurgical Center in Salt Lake City. The stimulus has been generated by society itself. Many students are dedicated to the proposition that new technology can circumvent the destruction of our environment, a concept which provides considerable motivation. At the governmental level, the recent concern for the quality of our environment has created action in the area of chemical processing both through imposition of stringent air and water quality standards, and through increased funding for technological research in this area. The National Academy of Sciences (NAS) gave impetus to this movement when it pointed up the need for development and support of such disciplines as extractive metallurgy, particularly chemical processing, in a recent report on Mineral Science and Technology. The recommendations in the NAS report have prompted governmental action on many fronts, including the Bureau of Mines, and have also given rise to direct legislation in the form of two bills -H. R. 3492 and S. 635- presently before Congress to a mineral engineering education. The report recommends that chemical processing technology (more generally extractive metallurgy) be developed by both new engineering techniques and unconventional chemical techniques such as application of the chemistry of nonaqueous liquids to mineral systems.

Jan 1, 1971

By Sir John Cadman

Since my previous review of the Persian fields, presented in 1929,' considerable progress has been made. The main feature of drilling development has been the delimitation of the Haft Kel field and its extensions. Although the limits have not yet been reached, a productive area of about 40 square miles has already been proved and it is now certain that the field will be of the same order of importance as the Masjid-i-Sulaiman field. Production to main pipe line from Haft Kel was begun in November, 1929, and to date about 4,500,000 tons have been produced. Normal production has continued from the Masjid-i-Sulaiman and Naft Khaneh fields. The search for oil in horizons below the main producing limestone is perhaps the most interesting and important exploratory drilling work in progress. Promising results have been obtained in the first well deepened in the Masjid-i-Sulaiman field with this objective, and the exploration of these lower formations is being continued. In this connection an allied program of geochemical research work on the nature of the oils and oil-bearing rocks of different horizons is at, present being undertaken. Masjid-i-Sulaiman Field Since the Haft Kel field was brought into production in 1929, production from Masjid-i-Sulaiman has been reduced in order to equalize to some extent the producing lives of the two fields. The production for the last four years has been as follows: m Approximate Equivalent in TonB Barrels 1929 5,434,071 38,038,497 1930 4,925,869 34,481,083 1931 4,248,086 29,736,602 1932 Approximately 4,500,000 31,500,000

Jan 1, 1933

By F. E. Crane, J. Downie

The general application of Darcy's law to natural rocks has already been challenged in the literature.1 The evidence shows that the permeability as calculated from the Darcy equation can be a function of the pressure drop and the salt concentration of the water phase. Most explanations for aberrant behavior involve clays and their properties and have been qualitatively satisfactory.Recently, however, Odeh2 revived the theoretical views of Yuster.3 Since Yuster's concept implies a fundamental error in using Darcy's relationship for two-phase flow, and not merely that conditions may limit its use, Odeh's experimental support arouses considerable interest. However, Odeh's work as presented is thought to to be inadequate. He has omitted important information about his materials and procedures; therefore, acceptance of his conclusions should be withheld. Since a clay effect is possible, Odeh should have been allowed space to present a more detailed account of the rocks which he used and the precautions which he took to avoid confounding the effects of clay and fluid circulation. In addition, it follows from Odeh's discussion that the oil relative permeability should increase as the viscosity ratio increases. Odeh presents data corroborating this deduction. It also follows that the oil relative permeability should decrease as the viscosity ratio of oil to water decreases. However, our results show that a high relative permeability, when once attained by using a viscous oil, may be maintained when that oil is replaced by an oil of much lower viscosity. EXPERIMENTAL PROCEDURE The results are shown in Fig. 1 and were obtained as follows. Sandstone cores. 3-in. long X l-in, in diameter and which contained clays, were saturated with

The following is an incomplete list of members and guests who called at Institute headquarters during the period June 10, 1919, to July 10, 1919. Anvil A. Anderson, Rapid City, S. D. Roy N. McBride, U. S. Army. R. Hay Anderson, Mexico City, Mex. R. S. McIntyre, Berkeley, Calif. W. A. Barnes, San Francisco, Calif. H. R. Maier, Brooklyn, N. Y. Bennett R. Bates, Denver, Colo. Wm. D. Mainwaring, Philadelphia, Pa. Harlan H. Bradt, Duluth, Minn. Wm. E. Milligan, Chrome, N. J. H. Brings, San Francisco, Calif. Willard S. Morse, Tacoma, Wash. Robert S. Burg, Ocean Park, Calif. Arthur Notman, Bisbee, Ariz. D. W. Butner, Congo Belge, Africa. P. Nugue, Chalon Sr. Saone, France. George A. Camphuis, El Paso, Tex. George A. Packard, Boston, Mass. Fred Canan, Denver, Colo. C. L. Petzel, New York City. Walter H. Coleman, Prescott, Ariz. V. Porreaud, Paris, France. Fred Crabtree, Pittsburgh, Pa. Fred S. Porter, Seattle, Wash. Ross E. Douglas, Rancagua, Chile. R. W. Prouty, Morenci, Ariz. F. A. Downes, Golden, Colo. Charles E. Prior, Brooklyn, N. Y. W. G. Eberhardt, Tucson, Ariz. Louis Ravicz, Minneapolis, Minn. Charles H. Fulton, Cleveland, Ohio. Wm. Reed, El Oro, Mexico. Wm. R. Grunow, New York City. E. J. Ristedt, Globe, Ariz. Orr R. Hamilton, Lansing, Mich. A. M. Rodgers, Middletown, N. Y. T. N. Havlin, St. Louis, Mo. J. C. Scoles, Salt Lake City, Utah. G. M. Henderson, Weston, Mass. C. E. Siebenthal, Washington, D. C.

Jan 8, 1919

By H. P. Reid

PORTLAND cement is manufactured under either of two general proc-esses, the wet or the dry. The raw materials in general consist of limestone, shells, marl, cement rock, clay, shale, blast-furnace slag, etc., so proportioned that when calcined the desired composition will be obtained. In the wet process the combined raw materials are ground to extreme fineness in the presence of water, to a resulting slurry of from 30 to 50 per cent moisture content. The moisture of the slurry may be reduced by thickening or filtering processes for feed to the cement kiln or the slurry may be fed to the kiln with its full percentage of water. The dry process differs from the wet in that the surface moisture of the raw materials is removed prior to grinding. For the drying of these materials heat is required and in most cases is produced by burning of raw fuel either on grates or stokers before the dryers or in suspension in the form of pulverized coal, oil or gaseous fuel. The power required for making the cement is sometimes purchased from outside sources; sometimes it is generated from the heat in the waste gases leaving the cement kilns, or generated at the plants direct from raw fuel. We have, then, as the possible requirements of fuel in the cement industry: (1) fuel for power generation, (2) fuel for drying raw materials, including coal before pulverizing, and (3) fuel for burning the raw materials to cement clinker. There is no essential difference in quality required in fuel for burning the materials by the wet and dry processes.

Jan 1, 1932

By Luis Emylnn Salas

If the ordinary wet method be attempted for silver-bullion containing tin, much trouble is experienced, varying with the amount of tin present. Even with a percentage as low as 0.05, the end-point is masked by a persistent turbidity, while with amounts ranging from 0.5 per cent. upward, the determination of the exact end-point is impossible, owing to the finely divided or colloidal metastannic acid resisting all efforts to cause it to settle, or to give a clear supernatant liquid. The object of the following experiments was to seek a remedy for these difficulties, and to find the conditions whereby the Gay Lussac method might be applied directly to these bullions. Material containing tin is met with frequently in bullion from Mexico or Bolivia; and tin is carried (sometimes in large quantities) in jewelers' sweeps. 1. A bullion was prepared containing Ag, 74; Cu, 25; and Sn, 1 per cent. A weighed amount was treated by the humid assay-method as if it were an ordinary bullion free from tin. Ten cc. of HNO, (1.21) was added, and the bottle was heated until all traces of

Jan 1, 1913

By N. A. Ziegler

CONSIDERABLE work has been and is being done on the changes of physical properties that take place in alloys at elevated temperatures, and much information on this subject is published. Much less is known, as pointed out by Rickett and Wood,1 about reactions between the alloys and atmospheric gases and still less is known about changes within the alloy itself under the influence of heat and given atmosphere. Moreover, most of the work published has been done on the alloys of "heat-resist-ing" type, in which chromium is an essential ingredient, the behavior of all other alloys being quite unknown, except perhaps of decarburization produced at the surface by oxidizing atmospheres. It has been shown' that iron, with total amount of foreign ingredients not exceeding 0.01 per cent, if heated in an oxidizing atmosphere at above 900° C., may be saturated with oxygen to 0.1 per cent. It was suspected that something of a similar nature may take place in iron-silicon alloys (transformer material), the mechanism of such processes being either a direct diffusion of oxygen into the alloy, or oxygen combining with silicon to form Si02 or more complicated (silicate) inclusions. Another possi-bility to be considered was that during annealing in oxidizing atmos-pheres, when scale is being formed, silicon may oxidize preferentially at the surface, thus impoverishing the alloy in silicon. In collaboration with Dr. T. D. Yensen,3 the writer set out to investigate this problem about two years ago in order to settle these questions.

Jan 1, 1934

By G. H. Ashley

THE Pittsburgh coal bed stands today: as probably the largest contributor of wealth of any single mineral deposit in the world. If it is not, what other deposit is? To the present it has contributed more than 2,530,000,000 tons of high-grade coal from Pennsylvania alone, worth nearly $4,000,000,000. Since 1910 it has added more than $2,500,000,000 to the value of Pennsylvania's mineral output. There is estimated to be about three times as much coal still in this bed as has been mined. To realize the full value of this wonderful bed it must be remembered that the figures given are for one State only. To them should be added the figures for the same bed from West Virginia, Ohio and Maryland. Furthermore, as known by man, this great deposit is only a fraction of its original whole. Outliers in Somerset County, Pa., indicate that its original extent in Pennsylvania in an east and west direction was more than two times its present extent. Add to that the northward extension as indicated by outliers in northern Allegheny, Armstrong and Indiana counties,, and it seems safe to say that its original extent was not less than three times the area at present underlain by it. And as the subjacent beds of the Allegheny group are found still further eastward and northward, it is at least a possibility that it originally covered an area many times its present area.

Jan 10, 1926

By Archer E. Wheeler, Milo W. Krejci

There are two general methods in use for the production of metallic copper from matte which are worthy of consideration : (1) the Welsh blister process, and (2) the converter process.' As practically all of the copper produced to-day is made in converters, we will give a brief outline of that process before proceeding with the special subject of this paper. Matte may be roughly defined as a mixture of the sulphides of copper, iron, nickel, silver, etc. In the converter process this is blown up to metallic copper in a modified type of Bessemer converter. The conversion of matte consists mainly in, (1) the removal of sulphur in the form of SO2, and (2) the slagging of the iron. With this brief statement we come to the two subdivisions of the process of converting mattes: Converting with acid linings. Converting with basic linings. Converting with Acid Lininys, This is carried out by lining the converter with siliceous rock or ore, which performs two functions: It protects the iron shell of the converter from the molten charge, and it furnishes the silica for combining with the iron as it is oxidized from the matte, to form a ferrous silicate. It follows from the second of these functions that this siliceous lining must be replaced from time to time, and in practice it has been necessary to reline converters every 8 to 40 hr., this time varying in different plants and even with different linings in the same plant, the life of a lining depending upon the grade of the matte treated, and upon the composition, the thickness, the tamping, and the drying of the lining.

Jan 1, 1914

By Adrian E. Ross

Diamond drilling through caving formations at depths greater than ZOO0 ft has long presented serious difficulty, generally solved either by casing or cementing. Casing is permitted only when the resulting smaller hole is acceptable, and cementing is frequently a problem at depth. A new method that injects cement under pressure at the desired location is an aid in diamond drilling deep holes. DRILLING through caving formations in diamond drill holes at depths greater than 2000 ft has long been a serious problem. These caving formations are normally passed only by casing the hole or by cementing the hole. Casing the hole is possible only when a resulting smaller hole is acceptable. In as much as only a limited number of reductions are economically practical, cementing is frequently considered the only method suitable for solving these problems. Cementing either by pumping a slurry into the hole or by dropping cylinders containing cement has proved satisfactory on holes under 2000 ft. In holes substantially deeper than 2000 ft these methods are not satisfactory, since during the pump- ing process cement separates out, whereas cylinders usually break before the bottom of the hole is reached. A new procedure, the injector method, apparently solves these problems.* With this method, cement is lowered in the hole in a cylinder, the cement being

Jan 1, 1953

By Henry Louis

IT can scarcely be considered a matter of doubt, in the present state of our knowledge, that the existence of, at any rate, two well-marked allotropic modifications of gold can be recognized, namely (a), the ordinary, yellow variety, and (b) the red, brown or purple, non-lustrous, amorphous variety. There are, indeed, not wanting indications that still other allotropic forms may be capable of existing. It is, for instance, possible that the green colors of gold obtained under certain conditions, or the black powder produced when the alloy of gold with potassium is decomposed by water, may represent further allotropic modifications, although this proposition is open to doubt. It call scarcely be pretended that the two first-named varieties have been absolutely isolated, yet it is, perhaps, quite permissible to speak of the ordinary and the amorphous modifications as having a proved existence. Ordinary gold is sometimes found crystallized in nature, although never in a state of purity. When gold is melted and, cooled slowly, its surface shows crystalline markings, and the fact that it is capable of crystallizing in the cubic system may be looked upon as established. When gold is produced by precipitation, the form which it assumes is dependent on the conditions of precipitation. G. Rose 1 says that gold precipitated by ferrous sulphate from very dilute solutions is so finely divided that no regular form can be recognized, but in more concentrated solutions the precipitate consists of minute cubes. When oxalic acid is used as a precipitant, the gold is coarser and forms octahedral crystals. J. Thomsen 2 has obtained similar results. Working with dilute and with highly-dilute

Jan 1, 1913

GEO. F. COMSTOCK,* Niagara Falls, N. Y. (written discussion?).-In this exposition of experimental data, the author infers, indirectly at least, that by the Charpy test information was obtained that led to the improve-ment of certain ordnance parts and that this improvement could not have been attained without the Charpy test. On examination of the data, however, it appears that the important point of the whole matter was that while the material had been accepted from the results of longitudinal tensile tests, it was really transverse ductility that was desired. The writer has no desire to attempt to detract from the value of the paper or to discredit the Charpy test in any way, but he would like to ask the author if he will not give more clearly his reasons for preferring the Charpy impact test for investigational and control work of this kind, over the more usual tensile test made in a transverse direction. The tensile test pieces are more cheaply made than the square notched impact bars; and from the former the limit of elasticity and the ultimate strength as well as, the ductility are obtained, while in the Charpy test only one property is measured. It does not seem that the author has shown a sufficient reason for favoring the latter test, when both it and the trans-verse tensile test served his purpose equally well in indicating the proper metal and treatment required for his special forging, and it is hoped that this reason will be given more clearly as a matter of useful general information.

Jan 11, 1919

By H. Landsberg

Biological as well as geological research has made very successful use of the qualities that the physicists have detected in radioactive substances. Outstanding examples for the vast new fields opened in this part of the border-land between the disciplines of geology and physics are the "radio thermal geology" [July, 1909, see 1 of "References" at end of paper] and all that is connected with the use of the radioactive disintegration clock for the age-determination of rocks and minerals [2]. In structural geology, not unlike to recent bi-ological uses of radioactive material, their "tracer" properties were helpful. Changes in Radon concentra-tion in soil-air, especially accumulations, led to hidden crevices and fault-zones. High contents of Radon in spring-water gave clues as to the types of rocks they had flowed through [3, 4). One specific application of the small admixtures of radioactive material, however, has only lately found some atten-tion and that is their use in linking beds of sedi-mentary strata otherwise only poorly identified be-cause of the lack of fossils or other characteristic properties. To be useful for this purpose, two con-ditions have to be fulfilled: (1) The amount of radioactive material per unit-weight of rock in a given horizon should be uniform over a large area; (2) this same amount should change fairly rapidly in the vertical succession of layers.

Jan 1, 1940