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By Robert F. Mehl

THIS essay is an attempt to present the elementary facts and ideas concerning the growth of crystals, especially of metals. Freezing, like all heterogeneous processes, is a process of nucleation and growth; it manifests itself in metallurgy primarily in the freezing of ingots. The preceding paper in this volume discusses nucleation; the paper to follow describes ingot solidification. The present paper will treat of the growth of nuclei to large crystals, embracing a long series of phenomena, many of which are familiar to metallurgists.† Crystal growth, it will be immediately noted, occurs not only in the freezing of metals, but in the freezing of all substances; and it is a prominent and familiar phenomenon in crystallization from solutions, aqueous or otherwise, and in crystallization from the vapor phase. It will be necessary to include such systems in this discussion, for so much of value to metallurgists has been learned from their study. Apart from this, so far as metals are concerned, it will be simpler to limit the discussion to the freezing of pure metals and of solid solutions. Other types of freezing-eutectic, peritectic, etc.-will be excluded, though they have much of interest and of importance. BASIC MECHANISM OF FREEZING Ideally, nucleation and growth processes can best be considered from the point of view of isothermal reaction and upon the assumption of random nucleation. In. such an ideal case, nuclei form at random, and at a characteristic rate either constant or changing with time, and grow to spherulites at a characteristic rate, constant or changing with time, Fig. I.. On the simplest assumption, the reaction rate-in this case the rate of freezing-is a resultant of these two component rates. The reaction rate equation may be written in terms of these two component rates. The formation of pearlite from austenite closely approaches this ideal case. The ideal case forms a very useful point of departure in considering real cases. Various factors of reality produce deviations from this assumed ideality. In freezing, the isotropic medium, the melt, passes to the anisotropic solid, the crystal. Crystals are lattices of atoms, and the unit cell is often referred to as a crystal unit. Rosenhain, many years ago, represented the nucleation and growth process on freezing in the manner shown in Fig. 2, feeling, intuitively, that there must be some crystal unit in crystal growth. It now appears that this may be true, though his picture requires much elaboration. The greatest deviation from ideality lies in the nonisothermal nature of the freezing process in metals. To approach this properly it should be recalled that many nonmetallic substances freeze slowly. Tammann, to whom we owe the classic approach, studied complex organic materials in which (as in the case of eutectoid steels at high

Jan 1, 1951

By Heribert Wiedemeier, Ali Khan

The tetnperature-conposition phase diagram of the syste,n MnS-CdS has been investigated over a range fro)n 600° to 1000° C. The small degree of solid solution on the MnS rich slde cornpared to the large CdS rich single-plzase region could be esplained by the difference in strzrctures of the cotnponents and the relative sizes of the metal ions. The change in lattice parameter as a function of cot)zposition is linear atzd jollous Vegavd's rule within experittzental limits of error. Mns and CdS have gained considerable attention in recent years because of their interesting solid state properties. In order to investigate such properties and thermodynamic quantities of mixed compositions of transition metal chalcogenides, it is necessary to establish their phase diagrams. Two earlier publications are concerned with the MnS-CdS system. Schnaase' found complete miscibility when MnS and CdS were co-precipitated in aqueous solutions at room temperature. However, there is evidence that the mixed crystals were not stable over the entire range of composition. roger's' investigation of the ternary system ZnS-CdS-MnS at 900" C indicates a solution of 48 mole pct MnS in CdS. During the course of this work which covers a temperature range from 600" to 100O° C, emphasis has been placed on the use of high-purity materials and well-defined modifications of starting products. EXPERIMENTAL Starting Materials. The stable green modification of MnS with NaCl structure was prepared by direct fusion of the elements and by chemical transport reaction. Stoichiometric amounts of manganese of 99.99+ pct purity and of sulfur of 99.999 pct purity from Gallard-Schlesinger Corp. were sealed in an evacuated quartz tube at a pressure of 10"5 mm Hg and annealed for 48 to 60 hr at 800°C. The quartz tubes used throughout this work were outgassed under high vacuum at a temperature of 90OU to 1000° C for 12 to 18 hr. For the synthesis of MnS by chemical transport3 stoichiometric ratios of elemental manganese and sulfur and small amounts of iodine were sealed under vacuum in a quartz tube, which was placed in the temperature gradient, 900/800-C, of a two zone furnace. Single crystals of MnS in form of platelets and octahedra were deposited at the cooler end of the tube. The manganese content was determined by EDTA titratin. A typical result of several analyses was 63.05 pct Mn which agreed well with the computed value, 63.14 pct. Commercially available CdS of 99.9+ pct purity, a mixture of the cubic and hexagonal forms, was converted into the hexagonal high-temperature modification by annealing CdS under vacuum in quartz tubes at 700° C for about 36 hr. As a second method, cadmium sulfide was transported in a temperature gradient, 70O° /650" C, with in vacuo sublimed iodine from the hot to the cooler zone of the tube. Large sized crystals in form of hexagonal columns and some platelets were obtained. An average result of the cadmium analysis by EDTA titration4 was 77.93 pct in good agreement with the computed value, 77.81 pct. Only the NaCl modification of MnS and the wurtzite modification of CdS were used for the solid solutions. Preparation of Solid Solutions. Finely powdered MnS and CdS samples were thoroughly mixed in molar ratios and compressed into pellets of about 6 mm diam and 2 mm in height at a pressure of approximately 13,500 atm.

Jan 1, 1969

By Arthur G. Levy, Henry M. Howe

$1. Introduction.—Any given piece of metal is made up of a very great number of grains, usually microscopic, each of which is a perfect crystal save only in outward form, with cleavage planes of low cohesion, geometrically arranged quite as in fie familiar non-metallic crystals. The plastic deformation of such a mass occurs chiefly through the slipping of the crystalline blocks of which each grain is composed along these cleavage planes, causing steps called slip bands to form on a previously polished surface. In this slip, the metal immediately adjoining each of the cleavage planes along which the slip takes place is thought to pass extremely rapidly through a very mobile state into the amorphous state, in which it is harder than the remaining still crystalline metal between the amorphous layers thus formed along the slip planes. Whether the slip planes below the surface in ferrite can be detected by cutting, polishing, and etching sections is in dispute; but if this detection is possible at all, it is usually made impossible by heating the metal even gently. In short, the change along the slip planes does not persist through heating, and it is thought not to persist through time even at the room temperature, nearly all the amorphous metal recrystallizing. The network in Fig. 22 and the parallel N.-70-E. lines in Fig. 21 are slip bands in copper. When plastically deformed metal is heated, certain parts of certain grains may twin, that is, their component crystalline units may rotate into a position, or more exactly into an orientation, symmetrical with the initial orientation and hence with that of the remainder of that grain. As seen in a microsection of a metal the twinned areas usually have parallel sides. The existence of twinning is recognized in metallic sections either by the presence of such parallel-sided areas differing in brightness from the adjoining metal, especially when seen under oblique light after etching, or more surely by the zigzagging of the slip bands which form when twinned metal is itself deformed again. Hence the usual procedure in developing twins is to deform plastically so as to cause the twinning tendency; to heat so as to allow the tendency to assert

Jan 1, 1915

The total estimated production of coal in the United States during the first century and a quarter of mining is shown in Table 20. This is the total of the production of the various states already shown in the various tables, and is believed to be the first statement of this sort made. No such table prepared from limited data can be accurate, but it is the writer's opinion that the totals shown are less than those actually produced. It was thought that this study would enable a reasonably accurate account of the movement of coal down the Ohio and Mississippi Rivers to be written. The searches made have shown that at this time the data do not exist from which such a study can be made, but some of the facts collected may be useful to future students.

Jan 1, 1942

By E. G. SINCLAIR

DRILLING wildcat wells in Wyoming differs a little from methods used in any other field. Here it is always advisable to start the hole as large as is convenient in order to carry each string of pipe as far as possible, so that drilling can be continued a thousand feet deeper if necessary, as there is always sand a few hundred feet ahead that really ought to be tested. This plan may seem ambitious, but if it is adhered to, it will save a great deal of trouble before the well is completed. In making the location, one representative from the operating department and one from the geological department should work together, so that the well may be in the best possible place for obtaining oil and the most feasible place to drill for the operating department. In Wyoming nearly all wells are drilled with standard tools, as with them a better log can be kept and better time made in completing the hole. The shales of Wyoming are very hard and do not mix well in a wet hole. The shale cuts into large pieces, too large to be circulated out of the hole, and forms a mat on the rotary which soon cuts off circulation. Then if this mat cannot be jarred from the bit, the drilling string has to be pulled and the mat cut off from the bit with a pick or an axe. I have seen standard tools come out of a wet hole with 10 to 16 in. of mat on the bottom of the bit. Rotary tools have drilled wells satisfactorily in the Big Muddy field and at Billy Creek, but in the other fields the wells have been drilled much more economically with cable tools.

Jan 1, 1926

Henry Louis, Newcastle-upon-Tyne, England (communication to the Secretary): I think very highly of the novel and ingenious device of Prof. Richards for analyzing the movement of the various elements of the jig; it is a method that certainly seems to promise valuable results, if we could only make certain that these various indicator-appliances have no effect upon the action of the jig. I would like, however, to suggest that in future experiments the connection between the plunger indicator-rod and the pencil should be made by means of parallel motions, so as better to reproduce the rectilinear motion of the piston. I should expect, if this were done, that the " curve " of the plunger in the Harz jig, at any rate, would be represented either by straight lines or else by quite regular curves, according to the method by which the plunger is set in motion; the apparent combinatioil of straight line and curve seems difficult to explain. With respect to the water-curve, I am afraid I am completely at fault, but no doubt Prof. Richards can explain my difficulty. In Fig. 2, the areas of the screen-side and the plunger-side of the jig are equal. If the piston be a fair fit and the bottom of

Jan 1, 1897

By F. F. McINTOSH

STEEL is a general name applied to the alloys of iron and carbon. These alloys always contain , other elements such as manganese, silicon, sulfur, and phosphorus. Manganese and silicon are usually considered to be alloying elements. Sulfur and phosphorus are regarded as impurities. Tradition has damned them both and, in addition to classifying them as impurities, has established the general impression that many of the ills of steels are the result of the presence of one or both of these elements. Metallurgists are inclined to question the soundness of this tradition. The fact that one blast-furnace plant is devoted entirely to the production of ferro-phosphorus which is used to rephosphorize basic open-hearth steel, and that sulfur is added to many heats of steel, indicates that these so- called impurities might also be classed as alloying elements, and that the tradition which damns them may not be altogether fair and well founded. A critical search through the technical literature on the effect of phosphorus on steel will disclose many references to its harmful effect. Most of these are general in character, but there has been a strong tendency to accept this traditional belief in the harmful effect of the element.

Jan 1, 1926

By H. R. MacMichael

IN the Chihuahua district of Mexico the first smelting was that inaugurated by the early Spaniards for the production of silver bullion. The ores treated were high in silver and lead. Silver-lead bullion was first produced and the lead then cupelled to waste, with the slag produced running from 5 to 10 per cent in lead and about 25 to 40 per cent silica. The ore was mined by peon labor, often being carried out of the mine on the backs of the men, and then transported by burros. Furnaces were of primitive construction, adobe or rock being used in the earlier period and some iron later when it became available. Blast was originally supplied by bellows manually operated. Such smelting was carried on to a greater or lesser extent until the latter part of the last century, and so extensive was it that many hundred thousand tons of leady slag remained to be treated in modern furnaces. In 1908 a smelter was placed in operation at Chihuahua by the American Smelting & Refining Co. At that time the ore was practically all oxidized and by a little selection, self-fluxing mixtures could be made, but with an average lead content usually under 10 per cent and sometimes as low as 7 per cent. The bullion produced would carry from 150 to 300 oz. silver per ton. The slag made approximated 30 per cent SiO2, 42 per cent FeO, 21 per cent CaO, and perhaps 3 per cent Zn. The ores varied from hard, coarse material which was passed through a crusher, to a considerable quantity of fines which had to be smelted as it came, as crushing the coarse was the only preparation for smelting.

Jan 1, 1933

By A. E. Wells, H. O. Hofman, R. P. Reynolds

A Discussion of the Paper of H. O. Hofman, R. P. Reynolds and A. E. Wells, read by title at the London Meeting, July, 1906 ; presented at the New York Meeting, April, 1907, and printed in Bi-Monthly Bulletin, No. 13, January, 1907, pp. 37 to 52. GEORGE A. PACKARD, Boston, Mass. (communication to the Secretary*) :-The very interesting results obtained by Prof. Hofman and his assistants came to my attention when I had temporarily assumed charge of the metallurgical department of the Missouri School of Mines, and had found it, pending the completion of a new building, lacking a furnace in which to roast ore preparatory to the customary lead blast-furnace run. An attempt at lime-roasting had been already determined upon, but the use of a charge which would make a slag of definite composition was a new idea. The results following were obtained by Messrs. Aubrey Fellows, J. C. Long, E. R. Wash, and Dr. T. C. Tseung, under my supervision. It is regretted that the data are not more complete; but the work was done simply incidentally to securing the desired ore for the blast-furnace, with no idea of obtaining any results of especial interest. It is submitted because of the metallic lead obtained, no notice of which has been seen elsewhere. The ore was an aggregate of several lots of concentrates, apparently from Missouri ores. The analysis follows, with that of the limestone and sandstone used, as far as made:. Ore, SiO2, 3.04; Fe, 0.77; CaO, 2.53; Pb, 68.74; Zn, 5.77; S, 13.9 per cent.; limestone, SiO2, 1.0 ; CaO, 54.35 per cent.; sandstone, SiO2, 99.8 per cent. The converter was made in the shops from a sheet of No. 14 iron riveted in the shape of a truncated cone, 20 in. in diameter at the top, 15 in. at the bottom and 22 in. high. A grate of No. 8 iron, 17 in. in diameter, with 130 s-in. holes placed at about 1.25-in. centers, was held in place by the shape of the

Jul 1, 1907

By J. M. Ross

THE Homestake mine is situated in Whitewood mining district, in the northern Black Hills of South Dakota, in the city of Lead, Lawrence County. The entire property, comprising 557 lode claims with a total area of 3343 acres, is held under United States Patent. The older claims were 300 by 1500 ft. under local regulations, the newer ones 600 by 1500 ft. The Homestake was discovered April 9, 1876, by Moses and Fred Manuel, and Jake Harney, who were drawn into the northern hills, from the Custer placer district, by news of the discovery of rich placer deposits in Deadwood Gulch. They located a number of additional lode claims and, in a short time, the whole country was covered with locations. The Manuel brothers built an arrastre the following winter and took out $5000. The next year the Homestake lode was sold to Senator George Hearst and associates, who organized the Homestake Mining Co. Other companies were formed to exploit other groups of claims and at one time five companies were operating on this deposit, the Father DeSmet, the Deadwood-Terra, the Caledonia, the Highland, and. the Homestake Mining Co. These companies, however, have been merged into the Homestake Mining Company. The first stamp mill, known as the "Eighty Mill," commenced operation on July, 12, 1878, and production has been nearly continuous since that time.

Jan 2, 1925

Allan Gibb, Mount Perry, Queensland, Australia (communication to the Secretary):—In drawing conclusions from his observations, Mr. Van Liew has apparently overlooked the reduction in weight that takes place in the content of the converter. The percentage-compositions of the matte, etc., are not directly comparable for determining the rate of elimination of the impurities; and, in the absence of exact weights (which in such an operation could not be obtained), it is necessary to determine the relation between the impurities and the copper with which they are combined at various stages, in order to get data that are comparable. Owing to a portion of the copper being removed in the slag, etc., the weight of copper in the converter is not a fixed quantity, but.it is sufficiently approximate to permit very reasonable comparison. The analytical data given by Mr. Van Liew, reduced to this basis (a ratio between the impurities and the copper with which they are combined), are shown in the table on page 958. From this table it will be evident that Mr. Van Liea's conclusions as to the source of heat at digerent stages are not quite correct. During the first 10 minutes, no iron is scorified, the heat being derived from the oxidation of the sulphur, of which 7 per cent. of the total is removed in this time. Prom

Jan 1, 1904

By W. M. Weigel

LESS advances in the technology of non-metallic minerals than for several years past mark 1931, and the cause is easily found. The universal depression and decreased markets for non-metallic as well as other mineral commodities has forced the producers to cut out all unnecessary expense and reduce operating costs to a minimum in order to keep going, even on a reduced output, and to prevent insolvency. The result. has been that but 'little research has been carried on, and such as has been completed has in but few cases been put into commercial practice on account of the expense involved in new equipment and plant changes. The trend in the industry has been more economic than technologic, and the greatest effort put on market studies and sales attempts to expand markets and scrutiny of present operating 'practice leading to reduction of cost of production. This tendency has been increased by highly competitive conditions and the buyer's market which has prevailed and to the fact that price has been a greater factor than quality in placing orders. Only in cases where improvements in technology would immediately and effectively reduce costs or where in special cases there was but little competition with almost a monopoly control has actual technical development taken place.

Jan 1, 1932

By B. DE MARE

THE No. 6 open-hearth furnace at the plant of the Worth Steel Co., Claymont, Del., is the first to be rebuilt according to the Kuehn system. This as well as the other five furnaces at Claymont, has a nominal capacity of 75 tons, but the actual charge is about 242,000 lb. No hot metal being available, the pig-iron is charged cold. Oil of low grade with an asphalt base is used as fuel. These two items have to be kept in mind when discussing the actual fuel consumption. Careful records have been kept covering a five weeks run and the following is a brief summary of them The time required to heat the furnace preparatory to charging from the time a wood fire was started until charging commenced was 36 hours. This, I understand, is much less than with furnaces of standard design. The draft of the furnace, as shown by a gage in the stack-flue, is 1.25 in. The maximum draft with new checkers on former runs was 1.50 in., this draft gradu¬ally decreasing as the checkers closed up. Both of the first helpers claim the present draft is all they need for the proper working of the furnace, and, as with the Kuehn regenerators the draft remains practically the same from beginning to end of a run, this is satisfactory.

Jan 1, 1929

By FRANK COLE

THE territory covered in this discussion includes all the states west of the Mississippi river. Agriculture is expanding each year in this section, but until recent years the application of commercial fertilizers as an aid to crop production was not practised to any great extent. The use of commercial fertilizers has increased somewhat, but is still on a small basis as compared with the tonnages used else- where in the United States. During 1928 these western states used 665,100 tons of all classes of fertilizer as compared 'with 7,933,600 tons used in the whole United States; or this western area, compromising near- ly two-thirds the land area, uses about 5 per cent of the total fertilizer. To show how large a tonnage one state may consume, North Carolina for the year 192s used 1,349,360 tons of commercial fertilizer or about twice the amount used by 22 western states.

Jan 1, 1930

By Frederick T. Williams

THE purpose of this paper is to discuss the relative merits of the large 31/8 in. machine and the small 21/4-in. tappett machine in driving development-headings ; and although the . data here presented were obtained from cross-cut headings alone, experience has shown that the results are equally true in drifting, raising and winning. Recently we drove two parallel cross-cuts through the same formation, using a 3k-in. machine at the breast of one cross-cut., and a 2k-in. machine of the same make at the breast of the other. The results of this work afforded an ideal comparison, since in both cases the headings were advanced through rock practically of the same hardness and breaking-properties ; the amount of sludging was equal, and there was no difference in the condition of the steel or the machines, in the air-pressure or in the experience of the operating-crews. Some operators in the Cripple Creek district contend that there is ground which cannot be handled with the small machine, the holes being too small to contain enough powder to pull the ground, etc. The results obtained in working the property of the Portland Gold Mining Co., however, show that the ground worked by them does not fall in this class. During a period of two years there have been driven, with the small machine, 4 miles and 308 ft. of development-headings, through a diversity of ground, including Pike's Peak granite (a coarsely porphyritic type of granite), highly indurated, andesitic or phonolytic breccia, true massive andesite, trachytic phonolyte, tuffas, and along dikes of decomposed basalt and hard phonolyte; in every instance a satisfactory record was made. The headings here described were driven through highly indurated, andesitic breccia, having a hardness of from 5.2 to 7.2

Mar 1, 1906

By Thomas T. Read

THE fact that certain types of ore-deposits have attained their present condition through the action of descending surface waters was, perhaps, first clearly pointed out by Posepny.1 The oxidizing effects of such waters were discussed by Penrose,2 and many papers dealing with this phase of the subject have subsequently appeared. That secondary enrichment of sulphide ores, however, might be produced by descending surface waters was not clearly understood until after the copper-bearing veins of the Butte district, Mont., had been carefully studied by the geologists of the U. S. Geological Survey, al¬though De Launay3 had suggested that sulphides might be transported from point to point and re-deposited in the zone above the level of ground-water. As a result of the study of the Butte district, two papers by geologists engaged in the work appeared within a short interval. The first by Weed,4 dealing with the enrichment of veins by later metallic sulphides: and the second by Ernmons,5 treating of the secondary enrichment of ore-deposits in general. In the latter paper it was pointed out that a typical vein of sulphide ores which has been subjected to the action of descending surface waters exhibits four zones,-an upper or surface zone, in which the changes have been mainly of removal, the products being typically oxides; a second zone of oxide enrichment, in which the less soluble metals brought from above have been precipitated as carbonates or oxides; a third zone of sulphide enrichment,

Mar 1, 1906

By A. S. Richardson

THe conditions that make necessary the mechanical ventilation of the Butte mines of the Anaconda Copper Mining Go. are due to a number of causes, all of which are incidental to the depth at which mining operations are now carried on, The main object to be accomplished, of course, is the reduction of the temperature and humidity of the air in the working places. Ventilation fans, both surface and underground, have been used for many years, but increasing depth has made the problem much more difficult. Further improvement in both ventilation equipment and methods, therefore, became necessary; and it is the purpose of this paper to describe the work planned and done under the improvement program. The mines of the district have been frequently described in various technical publications, so a description is unnecessary here. From a mine-ventilation viewpoint, compared with coal-mine ventilation systems, the problem is complicated by the fact that the workings to be ventilated are situated on a large number of steeply dipping veins which frequently intersect and are faulted, and also by the fact that the extent, or existence, of orebodies is not definitely known in advance of actual development work. For these reasons ventilation work cannot be planned in advance of actual operations, nor can such regular systems of ventilation as are used in working the more uniform and continuous bodies of coal be developed. When operations are conducted at a normal rate, about 10,000 miners are employed on two shifts, so that about 5000 men will be underground at one time. But as ventilation is necessary to reduce high temperature and humidity due, mainly, to natural causes, the quantity of air per man per minute is not a governing consideration in determining ventilation requirements. Most important among the numerous sources of heat and humidity in the mines are: heat generated during decay of mine timber; heat and humidity given off by mine rock and water; heat generated by oxidation of sulfide minerals; heat given off by electrical equipment; heat generated by mine fires (in certain localities).

Jan 1, 1923

By A. S. Richardson

THe conditions that make necessary the mechanical ventilation of the Butte mines of the Anaconda Copper Mining Go. are due to a number of causes, all of which are incidental to the depth at which mining operations are now carried on, The main object to be accomplished, of course, is the reduction of the temperature and humidity of the air in the working places. Ventilation fans, both surface and underground, have been used for many years, but increasing depth has made the problem much more difficult. Further improvement in both ventilation equipment and methods, therefore, became necessary; and it is the purpose of this paper to describe the work planned and done under the improvement program. The mines of the district have been frequently described in various technical publications, so a description is unnecessary here. From a mine-ventilation viewpoint, compared with coal-mine ventilation systems, the problem is complicated by the fact that the workings to be ventilated are situated on a large number of steeply dipping veins which frequently intersect and are faulted, and also by the fact that the extent, or existence, of orebodies is not definitely known in advance of actual development work. For these reasons ventilation work cannot be planned in advance of actual operations, nor can such regular systems of ventilation as are used in working the more uniform and continuous bodies of coal be developed. When operations are conducted at a normal rate, about 10,000 miners are employed on two shifts, so that about 5000 men will be underground at one time. But as ventilation is necessary to reduce high temperature and humidity due, mainly, to natural causes, the quantity of air per man per minute is not a governing consideration in determining ventilation requirements. Most important among the numerous sources of heat and humidity in the mines are: heat generated during decay of mine timber; heat and humidity given off by mine rock and water; heat generated by oxidation of sulfide minerals; heat given off by electrical equipment; heat generated by mine fires (in certain localities).

Jan 1, 1923

Jan 1, 1887

By George C. Branner

STATE geological surveys have had an interesting development in this country. They first appeared more than a hundred years ago. The fact that they have persisted and are now an important part of most state governments indicates the basic need for state departments con-cerned with mineral problems. The number of state surveys in 1941 (43) is at an all-time high, as is the aggre¬gate appropriation for their support for the fiscal year 1940-'41 ($1,600,708). The first surveys, those of North and South Carolina (see Fig. 1), made their appearance in 1820-'30, but neither survived that period. During the next two decades surveys were created in twenty states, but only three survived. In fact, it was not until the decade 1900-'10, when eighteen surveys were created and only five abolished, that these agencies became firmly established.

Jan 1, 1941