Search Documents

By Portland P. Fox, Berlen C. Moneymaker

The development, within recent years, of core drills capable of drilling holes up to 72 in., or even more, in diameter, has made possible an entirely new and valuable method of geologic exploration. Although little used until recently as an exploratory tool except in the United States, by the Tennessee Valley Authority and the Corps of Engineers of the U. S. Army, for the exploration of damsites, the large-diameter core drill may be used to good advantage in other types of geologic exploration. Its principal utility is that of supplementing, rather than replacing, other means of exploration. Although core is frequently recovered intact, the greatest advantage of large-diameter drilling is that the holes produced are large enough to be entered by the geologist and engineer, and thus afford an excellent means of examining undisturbed rock. The walls of the holes are smoothly cut, and in some rocks nearly or quite polished, so that the most minute details of structure and stratigraphy are clearly disclosed. Such features as faults, joints, bedding planes, weathered "seams," and beds or layers of soft materials, which are not always amenable to disclosure by cores recovered from small-diameter holes, are conspicuously displayed in the walls of large holes. Frequent reference to the drilling of large-diameter holes is made in engineering literature, but comparatively little emphasis has been placed on their value in geologic investigation. It is, therefore, intended that the present paper acquaint the geologist, as well as the engineer, with the large-diameter core drill and the technique involved in its use, and also with its advantages, disadvantages and limitations as an implement of geologic exploration. The Equipment The equipment generally employed in the drilling of large-diameter holes consists of a trunnion-type drill head mounted on a sliding base, which allows it to slide clear of the hole and thus permit the introduction

Jan 1, 1941

The finding of gold, in enriching quantity, along the streams that issued from the western foothills of the Sierra Nevada was the prelude not only to the birth of an organized mining industry in California but to the intensive exploration of the entire Pacific slope; it presaged the feverish exploitation of the mineral resources that the ubiquitous prospector soon uncovered all over our western domain. At first when this migration began, as typified by the rush of 1849, there was no time to examine the signs of ore that were to be detected along the track of adventure, and, it must be added, not many in that motley crowd of gold-seekers were qualified to interpret the signs if they had lingered to look at them. Such intelligent curiosity as a few of them possessed was directed to the finding of gold chiefly, if not exclusively; and their good sense in this respect can not be impugned, because in a new and remote country the less valuable metals and minerals are unlikely to be worth the winning. Many of those that came to California crossed the alkaline wastes and sagebrush prairies that extend between the Great Sal? Lake and the ramparts of the snow-clad Sierra; when coming overland they found it convenient to halt on the eastern slope and to pitch their camp in the valley of the Car- son river before they began the tedious ascent of the mountains and the final entry into the land of gold. One of the trails most used by these immigrants followed the Carson river to the mountain meadows south of Lake Tahoe and then descended among the pine-woods of Placerville, where they went to work with pan and shovel in the gold-bearing streams

Jan 1, 1932

By Wm. I. Weisman, Sid McIlveen

Sodium sulfate is an important industrial chemical, being one of perhaps a dozen or so chemical commodities produced and consumed in the United States in quantities exceeding 1 Mt/a. In recent years approximately half that production has come from natural sources, whereas 27 years ago only 25% was derived from these sources. Table 1 illustrates the history of production of natural sodium sulfate in the United States. Production of natural sodium sulfate from various types of deposits is the main source of this chemical in Canada and Mexico, and probably in Argentina, Chile, Spain, and the USSR. Mineralogy and Physical Properties Sodium sulfate is widespread in occurrence and is a common constituent of many mineral waters, as well as seawater. Atmospheric precipitation contains sulfate; it is one of the major dissolved constituents of rain and snow (Davis and DeWiest, 1966). Many of the saline lakes throughout the world contain varying amounts of sodium sulfate. Because sodium is usually the dominant cation, some workers make an anionic distinction, referring to lakes containing predominately sulfate as bitter lakes and those containing predominately carbonate as alkali, or soda lakes (Bateman, 1950). Sodium sulfate in its natural form is found as the hydrous salt mirabilite (commonly called Glauber's salt), and as thenardite, the anhydrous variety. The largest quantities occur in the form of mirabilite. Sodium sulfate is found in varying degrees of purity, from theoretically pure efflorescent crystals of mirabilite to combinations and admixtures of other salts and impurities. It is a common constituent of some brines; from this source much is extracted commercially. [ ]

Jan 1, 1983

By W. C. Ellis

Growth directions of tin, zinc, and cadmiun whisker crystals grown spontaneously fi-om the solid are summarized. In tin the edge and diagonal directions of the unit cell are jound with the exception oj- the [110] diagonal. In cadmiurn and zinc the usual dip-ections are a or a + c. The c direction has not been ohserwed. The gvouth directions from the solid are for the most part the same as those found for vapor-grozun crystals and are the ohserz:ed glide directions in plastic j-lou. Whisker crystals of these elements grown from the solid are not twinned. Specular lateral reflections are associated with planes of snall crystallographic indices. WHISKER crystals of tin, zinc, or cadmium grow spontaneously at room temperature in periods from months to years from thin electroplates and other prepared films of the respective metals.''2 It has been established that these crystals are single, but the question of twinning, such as occurs in whisker crystals of silicon,3'4 has not been resolved. Studies of morphology have been restricted to determinations of growth directions.5-' Whisker crystals are both straight and kinked. A few studies have been made on kinked whiskers including measurements of kink anglesa and determinations of growth directions,' but unfortunately not both on the same crystals. The kink angles, for the most part, for each species are grouped closely about a few unique values, but these values are not always those between observed growth directions in a single crystal. To supplement existing data, the growth directions, identification of lateral features, and presence or absence of twinning were determined with a Weissenberg goniometer by a method described elsewhereg on eight whisker crystals of tin, five of zinc, and five of cadmium. One kinked cadmium whisker was examined in detail. The specimens were needlelike, a few microns in cross section, and of the order of a millimeter in length. They were removed from electroplated substrates on laboratory specimens and commercial equipment after several years of growth as described in Table I. Since the specimens were less than 10 p in cross section they were ideally strong with no attendant risk of plastic deformation or damage in handling. Only deformation twinning has been reported for these elements. Therefore, twinning probably should not be expected in whisker crystals of these metals, particularly a twin plane containing the growth direction. A twin plane oriented in this direction was the one sought in this study. No examination was made for twinning at the boundary between kink segments except for one cadmium crystal. Well-defined reflections occur as a whisker crystal of tin, zinc, or cadmium is rotated about its growth direction when illuminated by a beam of light Although these reflections had been noted in earlier investigations, no study of them was made, probably because the earlier studies had disclosed also that

Jan 1, 1967

By H. Ries

THE term "clay" is applied usually to certain earthy rocks whose most prominent property is that of plasticity when wet. This permits them to be molded into almost any shape, which they retain when dry. Furthermore, they harden under fire. Clays contain hydrous aluminum silicates-the clay minerals-in appreciable amounts, but aside from this a number of other mineral grains, particularly quartz, may be present. Texturally clays are fine grained, and the so-called true clay particles are usually under 2µ in diameter. MINERALS IN CLAY Certain hydrous aluminum silicates that predominate in many clays are known as the clay minerals"." and are grouped by Kerr41 as follows: [ ] The kaolin group has been found to consist of a number of minerals with the same chemical composition but different crystalline structures .83 Kaolinite is commonly formed by the weathering of other mineral particles, particularly feldspar, but some deposits, like those in Cornwall, England,36 and others in the Washington-Idaho district, are thought by some to be of hydrothermal origin. Dickite and nacrite are thought to be due usually to waters of

Jan 1, 1949

By H. S. Jerabek, Charles S. Barrett, Robert F. Mehl

The precipitation of the nitride Fe4N from the solid solution of nitrogen in a Fe and of the phosphide Fe3P from the solid solution of phosphorus in a Fe both lead to the formation of structures that may be easily identified as Widmanstatten figures, within the meaning of the term as used in this series of papers. A complete solution has been obtained for the figure formed by Fe4N. The structure of Fe3P, however, is not fully known and a complete solution of this figure thus cannot be obtained; nevertheless, a study of this figure has furnished some new information. Precipitation of Fe4N from Alpha Solid Solution of N in Alpha Fe Constitution of System Iron-nitrogen A knowledge of the constitution of the whole of the Fe-N system is unnecessary for this work, though the recent studies by Eisenhut and Kauppl and by Lehrerz have clarified most of the moot points; it is sufficient for our purpose to state that a Fe of high purity dissolves 0.42 per cent of nitrogen in solid solution at the eutectoid temperature, 591' C., and that this solubility decreases at first rapidly and then more slowly until at room temperature the solid solubility amounts to approximately 0.1 per cent nitrogen.3

Jan 1, 1934

By Earl Hanson

FIRES in heavily timbered mines are disastrous, involving danger to both life and property. Some mines have been completely ruined or so heavily damaged that reopening them would not pay. Though few mines are entirely free from danger of fire, the risk is minimized by proper care and good design of plant. The Tintic Standard mine is at Dividend, Utah, in the famous Tintic mining district, about 60 miles south of Salt Lake City. The development of the mine was begun in 1907 by the late Mr. E. J. Raddatz and his associates. From the beginning, the work was hampered by high rock temperatures and the presence of high concentrations of rock gases such as carbon dioxide and nitrogen. Development work was carried on with great perseverance for nine years, and resulted in the discovery of ore in 1916. The total production of the Tintic Standard mine to Jan. 1, 1936, amounted to 1,664,388 tons of ore, having a gross value of .$61,996,719.

Jan 1, 1936

By R. Moldenke

The presence of nickel-chromium in pig iron made fro111 Cuban oles is so well known that the word "Mayari" is unconsciously associated with it. Since 1904, when exploration of the Mayari deposits of iron ore in northeastern Cuba was undertaken, there llas been increasing interest in these ores. Tlie Transactions contain numerous references to t1ieln.l This iron ore, which is shipped to the Tinited States in the nodulizecl state, has been thoroughly tested and found very valuable; the deposit covers over 25,000 acres and there is in sight over 500,000,000 tons of ore that, by systematic mining, runs practically constant in composition. With nickel and chromium present, also titanium in sufficient quantities to attract attention, as well as extremely low phosphorus and sulfur contents, the iron founder is naturally interested in the utilization of RInpari ore for pig iron for the better grades of finishrtl iron products. The present point of coilsn~iil)tion ol ILlapri ore is at Sparrow's Poi111, where hlayari pig iron of ally desiretl coml>osition is made. The composition of the dried ore is about as follows: Iron -29 per cent., silica 3 pc.r cent., nickel 1 per cciit., chroiniun~ 1.5 per cent., alumina 11 per cent., ant1 coinbined water 13 per cent. When nodulized, the iron runs up to nearly 56 per cent., the silic:~, :tlumi~i:i, nickel, and c~llromiurn are slightly highr than the arno~l~its just given. Practically all the, combined wntcr is driven off aild the iiodulizccl ore carries only a few- tenths per cent. of 1 C. M. Weld: Residual Rrolvn Iron Ores of Cuba. Tmns, (1909) 40, 299. C. K. Leitll nnd If'. J. Mcncl: Origin of Iron Ores of Central and Northeostr~n rlbn. Trans (1911) 42, 00. C. W. Hayes: May:~ri and Mos Iron-ore Deposits in Cuba. Idem, 109. J. E. Little: Maynri lron Mincs, as Developed by the Spanish-American Iron ('0. Idem, 152. J. F. Iie~np: M'ryari Iron-ore Dcposi(s. Trans. (1915) 61, 3. C. K. Leith 2nd N. J. Mead: Additional Data on Origin of Lateritic Iron 01cs or Eastern Cubn. Tmns. (1916) 63, 75.

Jan 1, 1923

By A. M. Kivari

OPERATIONS at the cement plant of the Permanente Corporation, in the hills about 45 miles south of San Francisco and 12 miles west of San Jose, are interesting to the members because of the adoption of modern hydrometallurgical methods for handling and beneficiating raw materials. Closed-circuit grinding, classification, hydro-separation, flotation, agitation, and thickening are familiar terms at this cement plant. These methods make it possible to process refractory limestone into suitable materials for the manufacture of modern cements. Construction of the plant, having originally a design capacity of 7000 bbl. of cement per day, was started in June 1939, and the first clinker was ground on the following Christmas Day. At present the capacity is about 12,000 bbl. of finished cement per 24 hr., most of the production being low-heat cement.† About 3130 tons of limestone, 620 tons 0f clay and 100 tons of gypsum are required daily for this output. Occasionally iron oxide is added to the clay to obtain the desired composition. This, together with the gypsum, is purchased from outside sources. Up to the present time, the corporation has produced low-heat, normal, moderate heat, moderate-sulphate-resisting, high-early-strength, oil-well, modified-oil-well, and plastic cements. Most of the present production is for Shasta Dam, near Redding, Calif., the total demand being 5,800,000 bbl, of cement. Following are some of the cement requirements of the Shasta Dam specifications: [PERCENT Chemical composition: Loss in ignition2.25 Insoluble residue0.75 SO32.25 MgO5.00 Uncombined lime in clinker (CaO)1 .25 Percentage of iron oxide to alumina ratio1.5 Compound composition: Tricalcium silicate (3CaO.Si02)Not more than 3,5 Dicalcium silicate (2CaO.Si02)Not less than 40 and not more than 65 Tricalcium aluminate (3CaO.Al2O7)Not more than 7 Tetracalcium aluminoferrite (4CaO.A12O3.Fe203) Not more than 0 Fineness:] The average specific surface in the bin sampled shall be not less than 1800 sq. cm. per gram and no individual sample less than 1600 sq. centimeters. Compressive strength: The average compressive strength-in pounds per square inch of three mortar cubes composed of one part cement and 2.75 parts fine testing sand, by weight, shall be equal to or greater than the following:

Jan 1, 1941

By Duane H. Haley

The century we live in has been an eventful time for the Third World, particularly the country of Peru. Although it will take one or two generations more to see its end and fully evaluate its scope, it is already clear that during the twentieth century, Peru has entered a dynamic industrial, economic, social, and political revolution. This century has seen the end of old governments, and the introduction of reforms which radically change complex traditional patterns. It also has marked the beginning of an era in which the government has elected to undertake, as a national effort, most of the future economic growth of Peru. For the most part, large multinational mining companies, which have helped to discover and put into operation large mineral and ore deposits in Peru, have been sympathetic toward this philosophy. Most big foreign companies, in addition to capital, brought with them to Peru an efficient technology, modern management, and an effective organization for the further processing, sales, and distribution of refined commodities. Nationalization of all basic resources, including mining, is the, trend-not, it is hoped, to the detriment of established technology and production.

Jan 1, 1974

By Henry Hebley

IN recent years, especially in the last decade, great interest has been shown and many advances have been made in the preparation and clean-ing of coal. In the major coal-producing countries, the percentage of tonnage cleaned has been increasing ever since 1924. As separating media, both liquids and gases are used, these generally being water and air respectively. Some systems, instead of obtaining separation by the velocity of the medium in which the coal is cleaned, depend on the density of water mixed with sand, or coal dust and shale, or with chemicals such as calcium chloride. In studying the results of coal-cleaning equipment, it will be observed that the efficiency of the cleaning apparatus lowers as the size of the coal decreases. This inability to obtain any marked improvement in the fines has been partly responsible for the installation of dedusting equipment, to remove the fine sizes from the raw coal prior to cleaning. When considering the possibility of installing dedusting equipment, many factors must be taken into account. Very often, but not always, both the ash and sulfur content of the coal increase as the coal size decreases. When bituminous coal, containing soft powdery fusain, is subjected to a wet washing process, the porous fines of the fusain remain in the small coal or in the wash water and delay the dewatering of the washed coal and increase the difficulty of clarification in settling tanks or thickeners. When a dedusted coal is cleaned by a wet process, the sludge recovered from the settling tank often runs so high in ash that the sludge can be discarded without further treatment and still the loss is small. Where treatment of the sludge is desired, however, froth flotation may be used to advantage if the size of the feed is below 1/10 in. Dust from the deduster can be treated in a similar manner. Fusain, which is usually found in the fine sizes, has often a much larger ash content than other coal.

Jan 1, 1933

By E. J. Whittenberger, F. N. Rhines

The formation of casting porosity is viewed as a nucleation and growth process with solidification shrinkage and gas precipitation as cooperative driving forces. Experimental evidence evaluating the individual contribution of each force confirms the major premise that microporosity is nucleated by gas precipitation. Additional data disclose the effects of the identity and quantity of gas, the temperature range of freezing, and the freezing rate upon the amount and distribution of porosity in light metal castings. POROSITY, as it commonly occurs in metal castings, has been ascribed to the contraction that accompanies the freezing of the metal, to the evolution of dissolved gases from the liquid during cooling and freezing, and, most frequently, to a combination of the two.'" "Pipe" formation is universally associated with solidification shrinkage; spherical "gas holes" are understood to be retained bubbles of gas; but the origin of microporosity, which usually exhibits an irregular or scalloped outline when viewed in cross-section, remains a subject of continuing debate.", ' The present research constitutes an endeavor to show what parts are played respectively by shrinkage and gas evolution in the initiation and growth of micropores and what factors determine their number, size, shape, and distribution. A preliminary outline of the mechanism of cavity formation in castings will serve to coordinate the experimental findings that will be reported and will at the same time provide a general theory of the origin of casting porosity. Basic to the mechanism of cavity formation that will be proposed are the following established facts: 1—that liquid metals and alloys contract gradually during cooling down to the freezing range, where a relatively large contraction, known as the "solidification shrinkage," takes place (exceptions in bismuth and gallium being noted);' 2—that the capacity of liquid metals and alloys for dissolving gases diminishes with cooling until, in the freezing interval, a large decrease takes place (various exceptions being noted and excluded from present consideration) ;.: and 3—that freezing proceeds counter to the direction of heat flow, the freezing front most commonly being composed of a system of tapering dendrite stalks and side arms which are coarser the lower the freezing rate and which protrude into the liquid for a distance that is greater the longer the freezing temperature interval of the alloy and the smaller the thermal gradient.' The mechanism by which voids are generated

Jan 1, 1953

By N. A. Rose, E. L. Spain

THIS study was undertaken primarily to determine the reasons for certain variations in the soundness of gravel aggregate taken from a number of widely separated points on the Tennessee River. Under laboratory tests, concrete made with these various aggregates in some cases exhibited marked differences in specific gravity crushing strength and durability. Gravel was studied in detail from Chattanooga to the mouth of the river and to a lesser extent from Chattanooga to Knoxville. The causes of variation were determined, and variational curves were constructed, which accurately predict the composition of aggregate at any point on the river and therefore its relative suitability for use in concrete. The aggregate at any point is suited for making sound concrete; the variance of suitability is due to varying percentages of sandstone and weathered material, which are less sound than other constituents. INTRODUCTION When it is stated that the aggregate from one point is inferior to that from another, it must not be construed to mean that the gravel is unfit for use. The classification upon which such aggregate ratings are based is largely arbitrary, thus inferiority or superiority is merely relative. Samples of gravel were selected from stockpiles at the dams of the Tennessee Valley Authority under construction, from the stockpiles of private companies along the river, and from samples taken by the gravel- exploration barge of the T. V. A. One hundred or more gravels of each size studied were selected at random by taking small handfulls while walking around the piles. These were separated according to the different mineral or rock constituents present, and the percentage of each constituent was obtained by counting. At least three such samples were taken from each size, and all checked with one another within a few per cent. The results were then averaged. In order to check on the accuracy of such sampling, a whole sample was taken from one point after the gravel was thoroughly mixed. The two methods gave approximately identical results. SOURCES AND TYPES OF MATERIALS The sources of gravel found in the Tennessee River are numerous and varied. The river itself traverses several geologic provinces, each

Jan 1, 1937

By R. Moldenke

The presence of nickel-chromium in pig iron made fro111 Cuban oles is so well known that the word "Mayari" is unconsciously associated with it. Since 1904, when exploration of the Mayari deposits of iron ore in northeastern Cuba was undertaken, there llas been increasing interest in these ores. Tlie Transactions contain numerous references to t1ieln.l This iron ore, which is shipped to the Tinited States in the nodulizecl state, has been thoroughly tested and found very valuable; the deposit covers over 25,000 acres and there is in sight over 500,000,000 tons of ore that, by systematic mining, runs practically constant in composition. With nickel and chromium present, also titanium in sufficient quantities to attract attention, as well as extremely low phosphorus and sulfur contents, the iron founder is naturally interested in the utilization of RInpari ore for pig iron for the better grades of finishrtl iron products. The present point of coilsn~iil)tion ol ILlapri ore is at Sparrow's Poi111, where hlayari pig iron of ally desiretl coml>osition is made. The composition of the dried ore is about as follows: Iron -29 per cent., silica 3 pc.r cent., nickel 1 per cciit., chroiniun~ 1.5 per cent., alumina 11 per cent., ant1 coinbined water 13 per cent. When nodulized, the iron runs up to nearly 56 per cent., the silic:~, :tlumi~i:i, nickel, and c~llromiurn are slightly highr than the arno~l~its just given. Practically all the, combined wntcr is driven off aild the iiodulizccl ore carries only a few- tenths per cent. of 1 C. M. Weld: Residual Rrolvn Iron Ores of Cuba. Tmns, (1909) 40, 299. C. K. Leitll nnd If'. J. Mcncl: Origin of Iron Ores of Central and Northeostr~n rlbn. Trans (1911) 42, 00. C. W. Hayes: May:~ri and Mos Iron-ore Deposits in Cuba. Idem, 109. J. E. Little: Maynri lron Mincs, as Developed by the Spanish-American Iron ('0. Idem, 152. J. F. Iie~np: M'ryari Iron-ore Dcposi(s. Trans. (1915) 61, 3. C. K. Leith 2nd N. J. Mead: Additional Data on Origin of Lateritic Iron 01cs or Eastern Cubn. Tmns. (1916) 63, 75.

Jan 1, 1923

By H. O. Hofman

The object of refining copper in the reverberatory furnace is to obtain a metal which will have the highest attainable degree of malleability, ductility and electric conductivity, and present at the same time a level surface when it solidifies in the mold after casting. These desirable physical properties are governed by the character of the impurities and the forms in which they are present, by the amount of cuprous oxide retained by the copper, by the quantity of gas held in solid solution, by the casting-temperature, and by the thickness of the casting. The effects of impurities, of cuprous oxide and of gases upon the mechanical properties of copper have been studied by Hampe1 in his classical paper " Colitributions to the Metallurgy of Copper." The most recent research into the effect of metals upon the electrical conductivity of copper is that of Addicks. 2 The influence of cuprous oxide upon the electrical conductivity has been investigated by Walker3 and Addick. 4 The absorption of gases has received attention by Hampe: Stah16 and Heyn 7 The effects of casting-temperature have been noted by Stahl.8

Jan 1, 1908

By Frank Somogyi, Donald H. Gray

Techniques for in-situ dewatering of tailings and slimes include evaporation, decantation, drainage under self weight, drainage by surcharging, and electro-osmosis. A promising technique for increasing drainage efficiency is a vertical, wall-drain system, which can be constructed in an impoundment concurrently with deposition of slurried tailings. The vertical drains, which can be constructed from sand or from the coarse fraction of a tailings stream, greatly speed the rate of consolidation of the fine tailings or slimes. The performance of a wall drain system and the semitidy of consolidation efficiency to certain variables or system parameters are examined. These parameters include the slime deposition rate, ratio of drain to slime permeability, drain width, and drain spacing.

Jan 1, 1979

By John A. Church

In a recent paper read before the Institute it was said of faults that "the sensible expression of the fracture is an earthquake." This notion, which has been expressed before, though usually as a theory and not as an admitted conclusion, is based upon the early belief that faulting is a violent rupture of the earth's crust. Faults are of different kinds, from great dislocations of the earth —hundreds of miles in length—down to the still more mysterious displacements with which miners have to deal. The latter are usually quite short, from 1000 to 20,000 feet in length, but are distinguished even above their greater brethren by the excessive pro-

Jan 1, 1893

By Y. C. Liu, W. R. Hibbard

An analysis of the relationship between the deformation and recrystallization textures in face-centered-cubic metals is presented. The analysis assumes that orientations of the secondary as well as the primary textures are related to the deformation texture. The effect of alloying elements on the recrystallization texture of copper-base alloys is also discussed. ROTATIONAL relationships based on prior orientations have been used to derive both the primary and secondary recrystallization textures."" This similarity suggests that, if the secondary texture arises from grains formed during primary recrystallization, as proposed by Dunn: and if primary recrystallization derives its lineage from the deformation structure, then the orientations obtained in secondary recrystallization .as well as those obtained in primary recrystallization should be related to the deformation texture. The following discussions are

Jan 1, 1956

By Walter Harvey Weed

(Mexican Meeting, November, 1901.) Among the many causes of that perplexing featurc of mineexploitation, the unequal distribution of the ore, the influence of the country-rock upon the vein-contents has long beer1 accepted as an important factor in certain districts, but the general application of the theory has not been proved. It is now possible to obtain trustworthy data with which to test the theory, and either to confirm or to overthrow this time-honored

Jan 1, 1902