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By E. D. Leavitt

I desire to state briefly my views respecting the great practical value of the Watertown testing-machine, and the necessity that exists, for an able permanent commission to supervise its operations, in order that the results of all tests made thereon may be properly worked out and rendered available for public use. It is doubtless known to the Institute that this machine has, for the past two years, been placed at the service of the public upon payment of a per diem charge. It was my privilege to be among the first to use the testing-machine, and the results of my first experiments were of such importance, owing to the great capacity and extreme accuracy of the machine, that it has since become my practice to have tests of all materials used in constructions that came under my charge, made at Watertown. As a conseqnence, nearly one hundred tests have been made on my account directly, and some two hundred and forty additional for work built from my designs. It may be confidently affirmed, that the factor of anxiety on all these structures is exceedingly small .m far as the quality of material is concerned, and it is undoubtedly a very great advantage for parties interested in construction to have

Jan 1, 1882

By L. S. Chabot

The bibliography of mining methods in the past few years has contained many articles dealing with the use of the diamond drill for blasthole drilling. In the Canadian mines, this method has been used with great success in stoping at Noranda, Aldermac, Waite Amulet, East Malartic and Sladen Malartic mines in the Province of Quebec. It has also been used at the Dorchester and Beattie gold mines in Duparquet, Quebec. The method has found useful application at Copper Mountain mine, British Colombia, and at Flin Flon mine in Manitoba. In the United States, the diamond drill blasthole method has been used at Cornwall Iron Ore Mines in Pennsylvania and at the Republic Steel Corporation magnetite properties in the Port Henry district of northern New York. In the Lake Superior iron district, the method has been used at the Anvil-Palms mine of Pickands, Mather and Co. at Bessemer, Mich., and is also used at the Book mine of the North Range Mining Co. at Alpha, Mich. Other companies in the district have also experimented in some degree with the method at some of their properties. This Paper is being offered as a prelimi- nary report on the use of the diamond drill method of stoping at the Book mine. Sufficient work has been done with it to prove its worth and it is the purpose of the article to present some results, operational details, equipment ideas and recommendstions which we have found in its use at our mine. Location and Description The Book mine is situated about a mile north of the village of Alpha, in the NE-NE1/4 and the SE-NE1/4 of set 12-42-33, between the Dunn mine and the Balkan-~~d~~~ mine, and about four miles southwest of the village of Crystal Falls, on the menominee Range of Michigan, The property was found to have ore near surface in sufficient quantities for open-pit operations and stripping was begun in the latter part of 1942 to prepare it for ore production in 1943. During 1943, 288,447 tons of direct shipping ore were produced from the open pit and 382,933 tons in 1944 While the mine was being operated as an open pit some 350,000 tons of lean ore were stockpiled for later treatment. This material is beilng treated in a washing and jig plant and concentrates are produced during the shipping season. The ore bodies at the Book mine are characteristic of the Menominee Range. They are found on the flanks of sharply folded anticlines which have a fairly steep pitch to the northwest. The open-pit operatiOns in 1943 and 1944 revealed two of these anticlinal structures. A detailed study and classification of the old diamond drill records, coupled with the information of some new holes drilled, has established the

Jan 1, 1949

By Leonard L. Melton, Calvin D. Saunders

The design and performance of many operations common to the petroleum industry depend upon the unique properties of a class of materials known as non-Newtonian fluids. The art of measuring and describing these properties, called rheology, has fallen far behind the field applica-tion of these fluids in this industry. Empirical methods are still employed although theoretically sound methods of analysis are now available. This paper illustrates a completely general method of analysis of the rheological properties of non-Newtonian fluids which id independent of the type of viscometer employed and also the rheological type of fluid encountered except those of a thixo-tropic or rheopectic nature. Values of the rheological properties of a fluid obtained using this method of analysis are based upon an absolute scale of measurement, eliminating the necessity of employ-jng arbitrary concepts of the flow properties of non-Newtonian fluids, The fundamental nature of this method of analysis is further demonstrated by evaluating the precision with which measurements have been made of these rheological properties by employing a dimensionless criteric: —the Fanning friction factor-Reynolds number correlation. INTRODUCTION Non-Newtonian fluids are not new in the petroleum industry. Particular properties of non-Newtonian materials have been recognized and used to advantage in drilling fluids and have found excellent application in the hydraulic fracturing process.'.' While usage of these fluids is not new in this industry, the art of measuring and describing their rheological properties is still in its infancy. This is reflected in the accepted method of evaluating drilling fluids, API RP 29, (1950), which recommends a one point "viscosity" measurement. These shortcomings are recognized by various groups in the industry and more adequate methods have been prposed.3,4 The efforts Of these people are to be commended; but, at the same time, the limitations of their method of analysis and viscometer must be appreciated. This method Of analysis is applicable Only to Bingham plastic fluids as is pointed out early in their articles. The consistency of a Bingham plastic fluid must also lie within the range of the viscometer which is also well defined by the author. It is believed that the apparent simplicity of this method of analysis and the utility Of Operation Of their viscometer will soon make the terms non-Newtonian fluid and Bingham plastic fluid synonymous as used in this industry; a tendency which has already been encountered. Application of this method of analysis to a non-Newtonian fluid other than a Bingham plastic can lead to erroneous results. The field of rheology has long been hampered by the adherence to arbitrary concepts of Of of the flow properties Of non-Newtonian fluids. This has resulted in the design and operation of viscometers so as to fulfill these concepts rather than following the more logical method of analyzing experimental data so as to yield a fundamental truth. completely Bingham proposed the concept Of plastic flow and yield asu rement. data presented by Buckingham could hardly be interpreted so as to substantiate this theory; but rather succeeded in establishing the fact that compliance with this flow concept could never be realized in the capillary tube vis-cometer.5 Bingham, in reply, sug-gested "Rather than complicate our formula, it would seem to me a much better plan to so change the conditions of flow that the formula will be linear... Reiner0 stated .This plan has been followed by me in collaboration with Miss Riwlin. . . . From the present paper (Reiner and Riwlin, 1929) it will be seen that it is possible to choose the conditions of flow so that the formula based on Bingham's law of plastic flow remains linear. This is realized in the rotation viscometer," Thus, a viscometer, with design and operation based on the Reiner and Riwlin equation for plastic flow, is restricted to a specific range of flow

Jan 1, 1958

By W. E. Curran

For years the geographical isolation of the Southern iron-ore district from the great producing centers in the North and East enabled it to meet its conditions and solve its own problems without regard to the practices and policies of other districts, but during the past few years distances have been shortened, practices and wages are being standardized, and these changing conditions have brought new problems to the South. Development of Pig Iron in the South The development of the pig-iron business in the South was very slow during its early years, gained speed rapidly in the latter part of the nineteenth century, reached its peak in 1918 and was on the decline before the depression that began in the latter part of 1929. The first blast furnace in Alabama was built at Cedar Creek in 1818, the year before the state was admitted to the union. In 1830, Daniel Hillman was sent from Tuscaloosa to found an iron works in Roupes Valley, where rich pockets of brown ore were numerous. He built a forge on the site of what later became Tannehill furnace and called it the Roupes Valley Iron Works. There pots, pans, plows, and horseshoes were made of metal from his Catalon forge; shaped by a large hammer operated by water power. Daniel Hillman died in 1832 and the ironworks lay idle until 1836, when Col. Ninion Tannehill bought the property, rebuilt the forge and, using slave labor from his plantation, operated and enlarged the works. By 1845 he had built two crude furnaces and did a flourishing business in ovens, skillets and kettles, which found a good market all over the South. In 1855, the plant was sold by Colonel Tannehill to Moses Stroup, an experienced ironmaster from Pennsylvania. He tore down the old furnaces and built a new plant, the ruins of which stand today (Fig. l). This furnace plant operated continuously until it was destroyed by Northern troops in 1865. It was never rebuilt, so that the shell in the picture is the same furnace that made many tons of guns and shells for the Confederacy during the war period.

Jan 1, 1938

By W. E. Curran

For years the geographical isolation of the Southern iron-ore district from the great producing centers in the North and East enabled it to meet its conditions and solve its own problems without regard to the practices and policies of other districts, but during the past few years distances have been shortened, practices and wages are being standardized, and these changing conditions have brought new problems to the South. Development of Pig Iron in the South The development of the pig-iron business in the South was very slow during its early years, gained speed rapidly in the latter part of the nineteenth century, reached its peak in 1918 and was on the decline before the depression that began in the latter part of 1929. The first blast furnace in Alabama was built at Cedar Creek in 1818, the year before the state was admitted to the union. In 1830, Daniel Hillman was sent from Tuscaloosa to found an iron works in Roupes Valley, where rich pockets of brown ore were numerous. He built a forge on the site of what later became Tannehill furnace and called it the Roupes Valley Iron Works. There pots, pans, plows, and horseshoes were made of metal from his Catalon forge; shaped by a large hammer operated by water power. Daniel Hillman died in 1832 and the ironworks lay idle until 1836, when Col. Ninion Tannehill bought the property, rebuilt the forge and, using slave labor from his plantation, operated and enlarged the works. By 1845 he had built two crude furnaces and did a flourishing business in ovens, skillets and kettles, which found a good market all over the South. In 1855, the plant was sold by Colonel Tannehill to Moses Stroup, an experienced ironmaster from Pennsylvania. He tore down the old furnaces and built a new plant, the ruins of which stand today (Fig. l). This furnace plant operated continuously until it was destroyed by Northern troops in 1865. It was never rebuilt, so that the shell in the picture is the same furnace that made many tons of guns and shells for the Confederacy during the war period.

Jan 1, 1938

By Charles Catlett

AN examination of the census reports' for 1880, which contain a large number of complete analyses of typical American iron-ores, indicates that the existence of barium sulphate in intimate association with iron-ore is rather unusual. Of 94 analyses reported there, but four show any barium sulphate, and the maximum content amounts to 3.04 per cent. The note of the occurrence of considerable quantities of barite in connection with certain iron-ores found in the Pinar del Rio Province of Cuba may be of interest. These deposits are found near the little village of Francisco, about 25 miles west of the city of Pinar del Rio on the Western Railroad of Havana. The principal ridges are anticlines, and consist of very thick deposits of sandy shales and slates containing a large number of little veins of white quartz which, by the gradual disintegration of the mass of the material, is left covering the surface. This quartz occasionally shows sulphide, but is generally barren of any such indication. At times lenticular masses of a more or less pure limestone were observed in these slates. The shales, which are of light color, are occasionally talcose. The formation would tentatively be classed as the Lower Cambrian, and the heavy ridges of comparatively horizontal limestone found in the anticlinal valleys as the Upper Cambrian. Along the crest of these slaty ridges deposits of iron-ore are found which are apparently in place, and were probably formed by replacement of masses of limestone similar to those noted elsewhere. The ready disintegration of the slates, and the

Jul 1, 1907

By C. H. Burgess

ON June 5, 1947, Secretary of State George C. Marshall in a speech at Harvard University outlined a plan for the economic recovery of Europe. The plan contemplated that the United States should provide assistance which would enable the European nations better to help themselves and to help each other to reconstitute from their war-torn lands conditions which would make possible decent standards of living. The Foreign Assistance Act of 1948 was passed in April of that year, and established the Eco-

Jan 10, 1950

By William Romanoff

As you are no doubt aware, virgin copper, tin and zinc are strategic metals today and little, if any, is available in the manufacture of brass and bronze ingots. The source of alloys used in the manufacture of implements of war are, therefore, from ingots made almost exclusively from the refining of available scrap. It is amusing to hear of the unusual physical properties of various alloys because they mean nothing unless the foundryman is able to produce good sound castings. A discussion therefore means little unless something is said about the relative foundry practice of the various brass and bronze alloys. Among the factors that influence the quality of castings produced are: (I) improper gating, (2) wrong pouring temperatures, (3) poor sand conditions, (4) bad melting practice, (5) faulty pattern equipment, (6) metal. It seems to be the consensus of opinion that about 95 per cent of defective castings can be attributed to the first three causes. Metal while a source of trouble at times, is probably the least responsible for foundry difficulties. As you all know, a molder never makes a bad mold. His first thought is to blame the "damn" metal as this is the path of least resistance. Let's consider the "damn" metal and how it is made. In the manufacture of ingot, scrap is collected at various sources and is shipped to the refiner either directly or through the scrap dealer or broker. It is usually sorted, although not always. In working toward a specified chemical analysis, weighed amounts of various grades of scrap metals are melted, and then oxidized by blowing air through the molten bath to rid the metal of detrimental impurities or reduce them to within specification limits after which they are skimmed off with the aid of some added fluxes. The bath of metal is then poled with wood, chemically tested before and after additions are made to bring it up to required specifications, and finally poured into ingots, after which a final chemical and physical examination is made. As mentioned above, the impurities have either been eliminated or reduced to the point where they meet the specifications of all Government Agencies or Technical Societies. Therefore, why worry as to whether castings are to be made from strategic virgin metals or secondary ingots from available scrap. Tests have continuously been made and it is a proven fact that physical properties are no better from virgin metals than from secondary ingots of the same composition. It is definitely more fool-proof to make castings from secondary ingot than from virgin metals because if an error is made in weighing the copper, tin, lead or zinc of the latter, the analysis is off balance. If an error is made in weighing secondary ingots, you merely have more or less metal but the analysis remains constant. Furthermore, when pure copper is melted. it is susceptible to reducing gases as well as oxides. Secondary ingot is already alloyed with natural deoxidizers such as zinc, etc., and the volatilization of the latter also tends to eliminate reducing gases mechanically.

Jan 1, 1943

By W. O. Borcherdt

THE 650-ton underground mill of The Empire Zinc Company of Colorado (a subsidiary of The New Jersey Zinc Co.) serves the Eagle mine at Gilman in the Battle Mountain mining district of Colorado, The topography is rough, the mine and mill being under Battle Mountain and the adit entrance in the north wall of the canyon of the Eagle River, which is here a steep gorge. The town of Gilman stands on a shoulder of the mountain at altitude 8975 ft., above sea level, along the Pike's Peak ocean to ocean highway and contains the company office and the usual facilities of a modern mining town. The railway contact is at Belden, altitude 8370 ft., at the bottom of the gorge directly below Gilman, where the westbound track of the Denver and Rio Grande Western Railroad is cut along the north bank and the eastbound track along the south bank of the river. A general description of the mine, mill and service facilities, with an account of the geology, character of the ore and methods of mining and milling having previously been published in a series of articles1, this paper will discuss with as little repetition as practicable the reasons for building the mill underground rather than as a conventional structure, the methods of construction employed and the experiences gained in what is apparently the pioneer plant of this type and extent. There is a large historical background for underground plant construction. From the dim past caves have been used for dwellings, stables, storage and shops. It was natural that where caves were available their many advantages led to their enlargement to suit convenience and where they were not available but the ground conditions, topography and drainage were favorable, to the construction of artificial caves. In the vicinity of Epernay, France, extensive underground chambers protect the manufacture and storage of champagne-an intricate and ingenious application of chemical engineering-and in recent years these plants have been mechanized by the installation of conveyor systems. In the

Jan 1, 1937

By M. S. Tsai, Y. D. Chuang, H. M. Wu

To contact the commercial OPAP-kerosene solution with CH3OH – H20 solution, we used the appropriate concentration of DOPAP / MOPAP solvent. By using this treated OPAP solvent, uranium can be recovered from wet-process phosphoric acid. Electric DC power is supplied on the dual side of the ion-exchange membrane of a specially designed box-type mixer settler. U(VI) is reduced to U(IV) in the cathode and U(IV) is oxidized to U(VI) in the anode. Uranium is extracted in the cathode by treating it with OPAP solvent. Next the uranium is stripped from the loaded OPAP solvent by concentrated phosphoric acid in the anode. After 300 hours of continuous operation total recovery of uranium is as much as 95%.

Jan 1, 1984

By G. Reinberg, C. D. Clarke

MOST underground mining operations are dependent on pumping installations to keep the mine unwatered. The reliability of such installations is obviously of paramount importance. The volume of water to be handled is often considerable, and the total head is relatively high. In these cases, both capital cost and operating expense of the pumping installations will become significant factors in overall mining costs. To insure reliability and to keep efficiencies, and hence operating cosl;s, within acceptable limits it goes without saying that mechanical maintenance of a mine pumping installation must receive scrupulous attention at all times. Large mine pumping installations today almost invariably use multistage centrifugal pumps, since positive-displacement units would not be economically competitive except under very unusual conditions of small volume combined with extremely high heads. Centrifugal pump maintenance, under ideal circumstances, would be confined to parts subject to normal running water, i.e., bearing surfaces, stuffing box packing, and shaft sleeves. Under adverse conditions, however, metal may be lost from the wetted surfaces of a pump by erosive or corrosive action of the pumped fluid, and maintenance costs can easily attain enormous proportions. The following definitions are those most generally used for the phenomena encountered. Erosion is a general term meaning mechanical removal of material from a surface. As applied to pumps, it may be the result of simple abrasion, such as that produced by suspended solid matter in the liquid being pumped. In common with other hy-

Jan 1, 1957

By Michael Tenenbaum, T. L. Joseph

Recent researches on the reduction of iron ores have stimulated interest in the effect of increased pressures within the iron blast furnace. From a physicochemical viewpoint, it seems logical to suppose that the increased pressure would increase the rate of reduction of the iron ore within the furnace. This increased reaction velocity would in turn be reflected in an increase in the output of the blast furnace. Any substantial effect of elevated blast-furnace pressures should accordingly be of both technical and economic interest to the operator. It is doubtful whether it is possible to increase the pressure in the stack of the blast furnace beyond two or three atmospheres without incurring severe mechanical difficulties. The benefits to be procured by elevations in pressure must therefore be restricted to pressures below two, or at the most, three atmospheres. Within this range it would seem both economically and mechanically feasible to modify the present design of the upper portion of the blast furnace to accommodate these more stringent operating conditions. This investigation was undertaken to study the effect of moderate pressures on the rate of reduction of iron ore with hydrogen. The use of carbon monoxide is contemplated for later work. Although any results that are obtained in the laboratory cannot be interpreted directly in terms of large-scale commercial operations, it is possible, through such an investigation, to ascertain the order of magnitude of the effects of higher pressure. A more quantitative conception of the effects that would result from the use of increased pressures in the modern blast furnace is needed. In some recent work, Diepschlagl found that, all other factors remaining constant, the degree of reduction of iron ores was much greater when carried out under pressure. Pressures as high as seven atmospheres were used. The degree of reduction was determined from the ferrous and ferric iron in the sponge iron. Results were obtained using both carbon monoxide and hydrogen at temperatures of 400°, 600° and

Jan 1, 1939

By Michael Tenenbaum, T. L. Joseph

Recent researches on the reduction of iron ores have stimulated interest in the effect of increased pressures within the iron blast furnace. From a physicochemical viewpoint, it seems logical to suppose that the increased pressure would increase the rate of reduction of the iron ore within the furnace. This increased reaction velocity would in turn be reflected in an increase in the output of the blast furnace. Any substantial effect of elevated blast-furnace pressures should accordingly be of both technical and economic interest to the operator. It is doubtful whether it is possible to increase the pressure in the stack of the blast furnace beyond two or three atmospheres without incurring severe mechanical difficulties. The benefits to be procured by elevations in pressure must therefore be restricted to pressures below two, or at the most, three atmospheres. Within this range it would seem both economically and mechanically feasible to modify the present design of the upper portion of the blast furnace to accommodate these more stringent operating conditions. This investigation was undertaken to study the effect of moderate pressures on the rate of reduction of iron ore with hydrogen. The use of carbon monoxide is contemplated for later work. Although any results that are obtained in the laboratory cannot be interpreted directly in terms of large-scale commercial operations, it is possible, through such an investigation, to ascertain the order of magnitude of the effects of higher pressure. A more quantitative conception of the effects that would result from the use of increased pressures in the modern blast furnace is needed. In some recent work, Diepschlagl found that, all other factors remaining constant, the degree of reduction of iron ores was much greater when carried out under pressure. Pressures as high as seven atmospheres were used. The degree of reduction was determined from the ferrous and ferric iron in the sponge iron. Results were obtained using both carbon monoxide and hydrogen at temperatures of 400°, 600° and

Jan 1, 1939

By Charles Catlett

Some years ago the writer was struck by what might be called the remarkable vitality of the Virginia furnaces during the panic of 1893; and attention was called to the fact in the American Manufacturer of February 8,1895. From the second half of 1892, which was a period of maximum output, to the second half of 1893, when the full effects of the depression had been reached, the output of pig-iron had fallen off in Illinois 85; in New York, 66; in Ohio, 51; in Tennessee, 44; in Pennsylvania, 28; and in Virginia only 15 per cent. It seemed a reasonable inference that the State which had thus shown its marked ability to meet hard times could make and market its product with a larger margin of profit than any of the other States. This was true at that time, and to a certain extent the reasoning still holds good; but my mistake was in not fully realizing the marked effect of the Mesabi development, combined with reduced economies in transportation, and the consequent advantage to those furnaces which were so situated as to utilize these new commercial factors. The effect of these factors is seen in comparing the second half of 1894 with the second half of 1892. New York had dropped off 44, Alabama 23, Tennessee 21, Illinois 19, and Virginia 16 per cent., while Pennsylvania had increased 5 and Ohio 10 per cent. While there is no question of the great economy which has been made possible for certain interests which are peculiarly situated with reference to the ores of the Northwest, it is yet too early to say what furnaces not so fortunate will have to pay for their raw material. Already an increase of twenty cents per ton of ore has been announced, based upon increased cost of production.

Jan 1, 1900

By J. McLaren Forbes

Geologists and engineers in charge of diamond drilling often have no practical experience in the work, yet they must direct the drillers. In discussing some of the problems that arise, the author of this paper has tried to remember the things he did not know about diamond drilling when he first came in contact with that work. The basic reason for most diamond-drill holes is to obtain information. The more thorough the understanding of the geological and engineering problems involved, the greater will be the benefit derived from a drilling program. One of the best methods to ensure some thinking before drilling is to record on the permanent drill log, before the hole is collared, the reasons for the work and the information desired from that particular hole. When the hole is finished, the information obtained should be recorded. Driller The choice of a diamond driller is very important. If no experienced driller is available, a competent miner who has a sense of responsibility and better than average mechanical ingenuity can do the work. The best answer to most practical drilling problems, from the standpoint of the person in charge of the drilling program, is the service of experienced diamond drillers or drilling firms. Equipment Drilling equipment should be adequate to put down the longest hole desired and handle the toughest ground encountered. The type of bit used depends upon the ground drilled. Experimenting with various bits and careful study of footage records are the best means of determining which to use. Under ordinary circumstances it is best to drill using an EX barrel when possible. The length of rod and core barrels that can be used depends on the size of the drill station. Also, the length of core barrel depends on the way the ground cores. In good ground as much core will be recovered with a 10-ft. barrel as with a shorter one, and with considerable saving of drilling time. A water pump is needed if the hole is so deep that the water pressure is not strong enough to wash out the cuttings, or if it is drilled at an angle that prevents full force of the water pressure. Instructions For an Inexperienced Driller 1. Never run a bit too long a time. When a bit seems to be "good for one more run," discard it. 2. Always let the rods down on bottom easily. Protect the bit from sudden shock. 3. Start the drilling slowly and easily. Do not put pressure on the bit too fast. Diamonds can break. 4. Be sure the water pressure is strong enough to clear the bit, but do not use more water than is needed, as it may wash away the core. Usually, if no core is recovered the hole is a total loss. 5. When dry-blocking, do not run without water longer than necessary as the bit may burn. 6. Be sure the rods are well caulked and tightly screwed together. If not well caulked they will lose water, and if not

Jan 1, 1946

By George M. Fowler, J. P. LYDEN

T HE relationship of geological structure to orebodies and to the great masses of chert in the Tri-State mining district is of such significance that it prompts a brief recital of the existing information regarding the various periods of structural deformation. We began to note a relationship between structure and orebodies early in our studies of the field, and further work revealed a like relationship of structure to the great masses of chert so commonly associated with the ore-

Jan 1, 1934

By Alvin Kaufman

ANTHRACITE mining in the United States is concentrated in a 480 sq mile section of north- eastern Pennsylvania. The producing area is broken up into four fields, known as the Northern, Southern, Eastern Middle and Western Middle fields. These areas represent intricately folded coal measures in synclinal residuals left by erosional forces. Destruction by erosion has eliminated some 95 pct of the original coal. However, discounting the 5 billion tons removed to date, 8 billion tons are believed to be still recoverable.

Jan 3, 1953

By Cushwa, C. C.

AT the Park Utah Mine, labor costs of stoping A have been reduced from 30 to 40 per cent. by the use of double-drum hoists and scrapers. The application of scrapers varies with the methods of timbering. In stopes, which must be timbered with square-sets or stringer sets, one method is used; another is used in wide orebodies that can be held open until filling is introduced; and still another in narrow flat veins. Nearly all the oreshoots at the Park Utah lie at less than 50" from the horizontal, and most of the ore is difficult to handle through flat chutes. Proper care is probably the most important requisite for successful scraping, as serviceable equipment can be obtained from several manufacturers. One capable mechanic, therefore, was put in charge of the scraper hoists. He visits every stope daily, oiling hoists and tail1 blocks, inspects all equipment, splices cables and changes "set-ups" when necessary; his pay has been a good investment. The Park Utah now has in use ten double-drum Turbinair hoists, and one Sullivan double-drum a. c. hoist of the same capacity and outside design as the air hoists. The electric hoist is slower than the air hoists and does not pass large boulders easily; it is, however, a very effective machine. The air hoists are fast, powerful and

Jan 1, 1925

Jan 1, 1918