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By J. G. Groppo

A series of performance studies have been conducted using counter-current column flotation to recover a marketable clean coal product from existing preparation plant fine waste streams. The test work was conducted at several preparation plant sites in Kentucky and Virginia and utilized a 0.15m (6 in.) I.D. column that was 5.79m (19 ft.) high. The refuse streams tested included both thickener feed and classifying cyclone overflow with a typical size distribution of 100 mesh X O. The percent solids of the column flotation feed varied from 1.5 to 15% while the ash content ranged from 30-60%. The concentrates produced contained 2-10% ash with BTU recoveries of nearly 90% using 0.12-1.25 kg/ton (0.25-2.5 lbs/ton) fuel oil and 0.12 kg/ton (0.25 lb/ton) MIBC. These results were consistent with or better than results obtained in preliminary laboratory scale column flotation evaluation. Test results from 7 different seams are discussed as well as scale-up relationships utilized to design a full scale installation presently in operation.

Jan 1, 1990

By Viktor Lishchuk, Olof Martinsson, Tobias E. Bauer, Elena Haller

Freely accessible and non-confidential real-life geological data sets from mineral deposits are desirable for the wide range of applications in research and education. However, publicly available statistical data are limited in their number and quality—they contain reduced information about geological, geophysical, geotechnical, chemical, mineralogical, and other relevant properties of deposits. This makes such data insufficient for scientific purposes. However, the amount of geological knowledge obtained for a variety of deposits in the past allows the construction of an idealized synthetic ore body model using analytical approach. Such a model could be used for education purposes and testing basic scientific theories, e.g., visualization of deposit structure; teaching sampling strategies; testing new algorithms for mine planning; or comparing geostatistical modeling methods. This paper presents an analytical approach to simulate volcanic massive sulfide (VMS) deposits and shows how synthetic deposit model can be constructed and further used for studying sampling with drilling and simulating folding and faulting.

Jan 14, 2021

By Joseph J. Wallace

1. The investigation shows that nine coal beds have been mined in Harlan County, of which the Harlan and Upper Elkhorn No, 3 are the most important from the standpoint of present production. Of less importance are the Hindman, Flag, Haddix, Wax, Fire Clay, Armburgy, and Upper Elkhorn No. 2. The Harlan, Upper Elkhorn No. 3, and Upper Elkhorn No. 2 beds contain the largest remaining known reserves. 2. Known measured and indicated reserves in all beds, based on a minimum thickness of 14 inches and 1,800 tons per acre-foot of coal in place, are estimated at 2,138 million short tons as of January I, 1932. Of this total, 1,956 million short tons is in beds 28 inches and more thick. Areas in each bed were omitted from the estimate because available data relative to the bed characteristics are too meager for making an estimate that conforms with the definitions of measured and indicated coal adopted for this study, Should future drilling or development prove reserves in these areas, such reserves should be added to the total estimated reserves.

Jan 1, 1954

By Stefan Larsson, Sadek Baker, Razvan Ignat

"This paper describes the execution of two full-scale field tests where a braced steel sheet pile wall interacting with rows of overlapping dry deep mixing columns was first excavated and then loaded to failure. The aim of the tests is to provide insight of the performance of dry deep mixing column rows located in passive zone and interacting with a retaining structure. The column rows were installed perpendicular to the sheet pile walls with two different area ratios, i.e. different distanced between the column rows. Both tests were extensively instrumented with inclinometers, pore pressure transducers, bellow-hoses, earth pressure gauges and strain gauges mounted on the struts. Results of the performedtests will serve as development of design methods for excavation support with columns.INTRODUCTIONDry deep mixing has been used with good results to strengthen the soil when excavations are to be performed in locations with thick soft clay deposits. An application that has increased in recent years is to install columns on the passive side of the retaining structure. Columns can be installed in different patterns but rows, grids or blocks are the most common arrangement. The use of column type ground improvement installed on the passive side of a retaining structure has been documented for a few field cases, Tanaka (1993), O’Rourke et al. (1997b), O’Rourke and McGinn (2006), Ou et al. (2008). By improving the soil on the passive zone, the passive earth pressure in front of the retaining structure is increased. This has proven to reduce the excavation induced deflections behind the retaining structure, reduce the structural forces (bending moment in the retaining structure, strut and anchor forces) and improve the safety against basal heave failure. The main focus of the conducted measurements within these cases has been on recording deflections and structural forces on the retaining structure and there is very little documentation available of the stress-strain behavior of the improved soil acting on the passive side of the retaining structure.Two full-scale tests of braced steel sheet pile walls interacting with rows of overlapping dry deep mixing columns were first excavated and then loaded to failure was conducted during the spring-summer of 2014. This paper briefly describes the test set up, instrumentation, test procedure and some selected results from one of the conducted tests."

Jan 1, 2015

To enable ammonium nitrate-fuel oil (AN-FO) to be used on an equal weight basis with nitroglycerine explosives, smaller diameter bore holes became necessary with consequent modifications to drill steel and burden on holes. Detonation of AN-FO in small diameter holes proved successful both with and without primer charges but some alterations were required to adapt anoloders to the smaller holes.Important factors in training all operators in the new charging method were the retention of improved fragmentation, avoidance of excessive overbreak and keeping wall rock dilution to an absolute minimum. The successful storage of ammonium nitrate in climatic conditions with daily temperature fluctuations above and below the critical 90°F has been achieved.INTRODUCTIONTechnical aspects of ammonium nitrate-fuel oil (AN-Fa) blasting agent are well covered in recent literature. This paper deals primarily with the manner of its introduction as the principal explosive underground at Great Boulder Gold Mines Ltd. and with the many problems encountered in the process. Following reasonably successful experimental firings in June 1962', using granular ammonium nitrate and an anoloder, permission was granted by theWestern Australian Mines Department to carry out test work in selected areas of the mine. The permit allowed for fuse firing only, and for a mixture of AN-Fa containing between 5t and 6 per cent fuel oil, with an adequate primer.The use of AN-Fa on an equal weight basis with nitroglycerine explosives, involved smaller diameter holes with alteration to ground burden and modification to drill steel.Initial tests indicated that it was apparent that AN-Fa could not replace gelignite on an equal weight basis if the...

Jan 1, 1965

By R. A. Cattell

With the surrender of the Japanese Imperial Government as a climax to the capitulation of the German High Command , the main objective of the Petroleum and Natural Gas Division pivoted from war assignments to its main normal functions . One of these functions is to give wide public distribution to valuable technical facts which the Division has obtained through research on petroleum , natural gas , helium , and related subjects . During the war years many engineering data and scientific facts could be released only on a restricted basis as reports to war agencies and others immediately concerned . Moreover , many of the wartime reports contained masses of detailed data that were prepared under stress to meet emergency schedules . For peacetime publication and application , these data must be reviewed , correlated , and rearranged so as to present the essentials in proper form . To illustrate , a wartime report of 50 pages might be resolved into one curve in a composite graph for a peacetime publication . Another factor affecting the orientation of the work of the Division is the broader horizon of research revealed by its war activities . Fundamental research and careful engineering analyses are just as important in time of peace as in time of war; in fact , they should be more important to the forward view , because under peace conditions disrupting influences that distract from the orderly acquisition of knowledge are minimized . Therefore , the concerted effort has been not to " salvage " the results of the war activities , but to evaluate them on the basis of their relative importance in the future economy of the country . Where wartime investigations have pointed to peacetime accomplishments , the effort has been to give the corresponding type of work additional emphasis . This adjustment can not be made hurriedly , but many of the necessary preliminary steps on the new course have been taken ..

Jun 1, 1949

By S. J. Hussey

Since the discovery in 1935 by Adams and Holmes that certain synthetic resins exhibit ion-exchange properties, many applications of the ion-exchange process have been made. There are two general types of ion-exchange resins. Cation exchange resins adsorb cations from solution, and these in turn may be replaced by other cations adsorbed under certain conditions. 'Anion exchange resins adsorb acids from solution, and the anion of the acid may then be replaced by other anions. It is reported, however, that certain anion exchange resins have a low capacity for anions of weak acids without the necessity of acid adsorption either directly or as an intermediate step. The adsorbed ions may then be removed from the resins by elution with an appropriate solution, and the resin is prepared for the next adsorption cycle by regeneration with another solution. Sometimes one solution, is used to simultaneously perform the functions of elution and regeneration. The first and probably the largest application is in the field of water purification. Other applications have been made in the production of high-quality foods for human consumption, in the recovery of valuable substances from solutions, in the separation or fractionation of electrolytes, and in several other fields, each of which has its specific applications, variations, and possibilities. Ion exchange resins also have been highly useful in perfecting techniques of laboratory analysis and research.4/, 5/, 6/

Jan 1, 1948

By Albert L. Toenges, Louis A. Turnbull, Alonzo W. Quinn, J. M. Schopf, Arthur Neale, R. F. Abernethy

"INTRODUCTION The fuel requirements for industrial and domestic consumers in New England, in normal times, are supplied almost entirely by fuel oil, anthracite, and bituminous coal. A shortage of these fuels occurred during the war. This shortage was caused by (1) The diversion of oil to military uses; (2) the use of railroad and boat facilities that ordinarily would transport coal for the transportation of war materiel; (3) the inability of coal mines to apply the increased demand for coal which resulted from the conversion from oil to coal by domestic and industrial consumers; and (4) the increased demand of war industries for coal. Because of this critical fuel situation, an investiga¬tion was made of possible sources of fuel nearer to points of consumption in New England. Meta-anthracite, which is a satisfactory fuel for some purposes, had been mined in Massachusetts and Rhode Island many years ago. However, the introduction of freer-burning anthracite and bituminous coal into New England markets resulted in the abandonment of these mines.The coal mined in the vicinity of Portsmouth on Aquidneck Island, Newport County, R. I., had been used successfully for smelting copper ore and for fuel. It is reported that this coal is less graphitic than the material mined at Cranston near Providence, R. I. The coal is meta-anthracite and does not burn freely. However, improved equipment for burning coal has been developed, and if minable reserves of meta-anthracite should be found, methods of burning it probably could be devised.The purpose of this investigation was to determine sources of additional fuel. Since meta-anthracite mined at Portsmouth had been used with some success, an investigation was undertaken to determine the characteristics and continuity of the beds in this area."

Apr 1, 1948

By Liaqat Ali, Robert Chapman, Asghar Ali, Mohammad Tahir Shah, Seema AnjumKhattak, Mohammad Farhan

Alluvial gold is abundant in the Quaternary deposits of the Kabul and Indus rivers in District Nowshera, Khyber Pakhtunkhwa, Pakistan. Understanding the provenance of alluvial gold using morphology and elemental composition could be helpful in developing an exploration strategy of regional benefit. Detailed morphological studies of gold grains revealed high flatness index values which are indicative of a distal source. Compositional studies of 58 gold grains using SEM and EMPA showed broadly similar Ag ranges (1– 15 wt%) for each sample and occasional Cu values in individual gold particles to 0.4 wt%.Whilst the Ag profile is not diagnostic, the Cu values are compatible with derivation from either porphyry systems or ultrabasic rocks. The complex geology of the drainage catchments could host gold mineralization of other styles, but larger sample suites would be required to refine the current interpretation to establish whether particles which are simple Au-Ag alloys could be derived fromorogenic or epithermal sources. This scoping study has demonstrated that the compositional and morphological studies of gold grains are useful in providing information regarding the nature and location of the source of placer gold in areas where there is limited information on the nature and location of in situ mineralization.

Oct 6, 2020

By J. J. Jakowsky

[The legislation in many States against the present method of producing carbon-black by the incomplete combustion of natural gas, and the continually increasing demand for gas for otter purposes, indicates that the supply of carbon-black may Gradually be decreased and that new methods for its production, utilizing a greater parentage of the carbon in the has should be developed. In the course of investigations of the effects on hydrocarbons of high voltage discharges, it was noted that under certain conditions natural gas could be decomposed and that carbon-black could be produced. The effects of several tyres of electrical discharges on natural gas have, accordingly, been studied' in order to find out the fundamental factors underlying the reactions and their possible influence in the recovery of a greater part of the carbon content of natural gas than is now possible. Present commercial plants using natural gas for the manufacture of carbon-black recover from 0.9 to 1.5 pounds of carbon-black per thousand cubic feet of gala consumed, or less than 5 per cent of the total Gabon in the gas: It should be noted, however, that the, present methods involve heating the gas to incandescense by burning it as a luminous flame, and a considerable part of the gas is thus consumed as a source of hest. If this heat can be supplied from some other source, or if a more efficient method of applying the energy con. tamed in part of the gas, to the decomposition of the rest of it, can be worked out, then a greater yield of carbon-black per thousand cubic feet of gas care be expected. The present abort paper contains a brief summary of tie investigations so far conducted upon natural gas.]

Jan 1, 1922

The principal activities of the Bureau of Mines Explosives Research Center (now Safety Research Center) during fiscal year 1968 (July 1, 1967, to June 30, 1968) are reviewed in part 1. Part 2 presents short abstracts of the publications issued during this period in the Bureau series and in other media. Part 3 describes a short study on the thermal decomposition of RDX and HMX not destined for publication elsewhere. ACKNOWLEDGMENTS The Bureau gratefully acknowledges the support received through cooperative agreement in fiscal year 1968 from The Manufacturing Chemists Association.

Jan 1, 1970

By H. E. Powell

A laboratory mineral-dressing investigation was conducted by the Federal Bureau of Mines on four limonitic and four sideritic iron ores from the North Basin of the east Texas iron-ore district. The samples, composited from drill cores, were considered representative of the iron-ore reserves of the area. The objectives of this research were twofold: (1) To devise a mineral-dressing method whereby the yield from currently mined east Texas iron ores might be increased and the grade improved, and (2) to extend such treatment to include the lower grade ferruginous materials that are not amenable to beneficiation by simple washing and, therefore, are not being exploited. Of the mineral-dressing methods used in this investigation, magnetic separation of roasted are was shown to be the most effective. Results show that, by this method, a laboratory recovery of 82 percent of the iron is attainable at a grade surpassing that obtained by current plant practice and that both limonite and siderite are amenable to concentration by the process. The existence of large deposits of iron are in eastern Texas has been recognized for over 100 years. These ores were first exploited during the Civil War and were mined intermittently until about 1911. From that time until 1944 when the Defense Plant Corporation financed the erection of three blast furnaces to use these east Texas ores, production was almost at a standstill.4/

Jan 1, 1960

By A. Ignatieff

Introduction Some interest is being shown in Canada in underground gasification of coal and, as developments have now taken place in several countries of the world, it is thought that a review of progress, particularly from the viewpoint of a mining engineer, may be of interest. The literature on the subject, and notably that of Russian origin, is already very voluminous. The various methods of underground gasification of coal have evolved from initial attempts to employ underground workings as gasifiers of previously fragmented coal or to use some method that involves little or no preparatory work underground. The 'stream' method, shown schematically in Figure 1, has been the only one used in tests to date in countries outside the U.S.S.R. Other methods, involving preparatory work underground prior to gasification, are the early 'chamber' method, where fragmented coal was gasified in rooms between inlet and outlet entries, and the underground borehole' method, illustrated in Figure 2, where gasification is developed in a succession of boreholes which are temporarily sealed and then abandoned in turn after gasification. The stream method appears. to be particularly suitable for pitching seems as it is claimed that the pitch prevents ash accumulation or serious blockage from roof falls, and it also aids the circulation of the stream. As a considerable proportion of Canadian medium and high-rank coal seams are inclined, it would seem that, at least at the outset, the stream method or a modification thereof would be the one most applicable to all but the Saskatchewan lignite fields and the flat domestic-coal fields of Alberta.

Jan 1, 1949

By John C. Gagliardi

The U.S. Bureau of Mines, in cooperation with Carter Mining Co., conducted vibration tests of four off-road vehicle seats. The purpose of the tests was to determine which seat provided the best vibration attenuation under laboratory conditions. Laboratory tests were constructed to simulate the mining vibration environment within the limitations of the test equipment. The acceleration test levels and corresponding response of the seats were low compared to ISO 2631's fatigue-decreased-proficiency time limits. Two of the seats employed mechanical suspensions and two seats employed air suspensions. The seats were tested using a 22,241-N (5,000-lbf) electrodynamic shaker. Mechanical suspension seats were tested with various preload-to-mass ratios (PMR's) and cushion densities. Air suspension seats were tested with various air pressure levels and seat cushion densities. Air suspension seats provided good vibration attenuation if pressurized greater than 552 kPa (80 psi). Mechanical suspension seats' attenuation performance decreased if the PMR exceeded 9.8. Seat cushions of lower density provided less vibration damping.

Jan 1, 2010

By T. S. Lundy, J. I. Federer

Chemically purified Zr95and Cb95 have been used in determining self-diffusion coefficients in the bcc phase of iodide zirconium over the temperature range of 900o to 1750°C. The temperature dependence of the diffusion coefficients could not be described by the usual Arrhenius-type equation over the entire temperature range. Values of the apparent frequency factors (D0)a and activation energies (Q)A for ZR95 varied from 4.8 x 10-6 to 2.5 x 10-2 sq cm per sec and 20,700 to 46,900 cal per mole, respectively, between 900°and 1750°C. Similarly, for Cb95, values of (Do) a and (Q)A varied from about 2.4 x 10'5 to 0.25 sq cm per sec and 26,500 to 56,800 cal per mole, respectively. The data may be described in terms of the a to ß transition temperature of 1136 °K and the absolute temperature of the diffusion anneals by the following eauations: SEVERAL studies on the diffusion of Zr95 in zirconium have been reported.1"5 The values of the constants contained in the usual Arrhenius-type equation for describing the temperature dependence of the diffusion coefficient, D = Do exp [- Q/(RT)], are summarized in Table I. The reported values of Do, the frequency factor, and Q, the activation energy, are seen to vary by factors of about 60 and 1.6, respectively. Examination of the data from any one study indicated reasonable consistency of measurements. The large discrepancies of over-all results, therefore, cannot be explained on the basis of experimental scatter. One possible explanation for the differences in results could be a varying impurity content of the zirconium. Another possibility is that the radioactive daughter, Cb95, influenced the values of some of the determined diffusion coefficients. Therefore, the first of the three purposes of this study was to reconcile the large differences in diffusion results that have been obtained. Several empirical relations have been proposed to relate the diffusion coefficients in solids with physical properties, such as the absolute melting point, the heat of fusion, and the heat of sublimation.

Jan 1, 1963

By P M. Ashley, M T. Costelloe

The Mary Kathleen tailings storage facility (TSF) contains 7.1 Mt of uranium mill tailings. This waste repository was rehabilitated in the mid-1980s using a multibarrier dry cover. At the time of mine closure, it was predicted that acid mine drainage (AMD) generation would not eventuate and that uranium, heavy metals and radionuclides would be adsorbed within the tailings and not seep from the TSF into the environment. This study reports on the environmental status of the TSF. Gamma-ray measurements indicate an intact dry cover of the waste repository. However, seepage (~0.5 L s-1) of acid (pH 5.71), saline (0.31 per cent), high conductivity (8.8 mS cm-1), slightly oxygenated (DO 2.6 mg L-1), radioactive waters occurs from the toe of the tailings dam into the former evaporation ponds and local drainage system. Seepage waters are calcium-magnesium-sulfate rich with elevated Fe, Mn, Ni, U and Zn values. Oxygenation of tailings seepages causes the precipitation of Fe and coprecipitation and adsorption of other metals (Pb, U, Y), metalloids (As), rare earth elements (Ce, La) and radionuclides (U-235, U-238, Th-227). In contrast, Ba, Ni, Sr, Mn, P, S, Ca, Mg, Na and K as well as Ra nuclides (Ra-226 and Ra-228) remain in solution until pH neutralisation and evaporation lead to their precipitation in efflorescences and sulfate-rich evaporative sediments further downstream. Dry capping of Mary Kathleen uranium mill tailings has resulted in physical containment of the wastes. The dry cover shows no signs of erosion and radiation levels are within acceptable limits. However, the flow rate of surface seepage from the TSF occurs at a much higher rate than predicted. Also, the neutralising potential and adsorption capacity of the tailings and underlying aquifer were overestimated at the time of mine closure. AMD has developed mobilising metals, metalloids, rare earth elements, alkalis, radionuclides and sulfate from the waste repository into surface water seepages.

Jan 1, 2003

By Robin N. Adair

Abstract -The Halfmile Lake stratiform volcanogenic massive-sulfide deposit consists of pyrrhotite­ rich breccia-matrix sulfides and pyrite-pyrrhotite-rich layered sulfides that form a laterally continuous sheet stratigraphically underlain by an extensive pyrrhotite-chalcopyrite-quartz stringer zone. Mineralization is hosted by a sequence of felsic pyroclastics and volcanic-derived, fine-grained metasediments. The proportion of volcanic to sedimentary rocks indicates increasing vent proximity from southwest to northeast across the deposit area. Fine- to medium-grained felsic pyroclastics and roughly equal amounts of fine-grained metasediments comprise the stratigraphic footwall to the mineralization. Quartz-feldspar porphyritic bodies cut this sequence and may have provided the heat source for exhalite activity. Felsic tuffs, locally crystal-rich, and lesser amounts of metasedimentary rocks make up the immediate stratigraphie hanging wall. This sequence is stratigraphically overlain and locally interfmgered with matie volcanics that contain substantial proportions of felsic fragments. Deposition of sulfides post-dated the beginning of felsic volcanism, which places the deposit in the middle of the Lower Tetagouche Group. Compositions of the volcanic rocks range from basait to rhyolite and exhibit sub-alkaline affinities. Strongly overprinted whole-rock, trace-element, and REE geochemical signatures resulting from mineralizing hydrothermal activity confirm the genetic relationship be­tween the stringer zone and the mineralized sheet. Large-scale D1 folding has overturned the entire sequence. D1 thrust faults and related sheath-like folds have profoundly affected sulfide distribution. D2 is manifested by a penetrative S2 foliation, and D3 is represented by large-scale open folds.

Jan 1, 1992

By Philippe Caudal

This paper presents a case study in which a slope failure was observed on the west wall of the LAB Chrysotile mine in the vicinity of the main ramp in January 2010. Airborne LiDAR results were used to evaluate slope geometry before and after the failure occurred. Back analysis of the failure was performed to assess rock mass properties at the slope scale using various numerical techniques: limit equilibrium, finite elements and fracture networks. The various approaches correlated well with field observations.

Aug 1, 2013

By J. A. Ober

"In 2016, the estimated value of total nonfuel mineral production in the United States was $74.6 billion, a slight increase from the revised total of $73.4 billion in 2015 (Table 1). Increased construction activity spurred increased production of industrial minerals, especially those used in infrastructure and residential construction. Although starting the year relatively low, prices for several metals, especially for some of the precious metals, began to trend upward. Decreased production of most metals produced in the United States, however, contributed to an overall decline in the value of metal production.Several U.S. metal mines and processing facilities were idled or closed permanently in 2016, including iron ore mines in Michigan and Minnesota; three primary aluminum smelters in Indiana, Missouri and Washington; one secondary zinc smelter in North Carolina; a titanium sponge facility in Utah and titanium mineral operations in Virginia. In addition, in May, the weekly average rig count for oil and gas drilling reached its lowest level since the 1940s when that measurement was first recorded. The reduced drilling activity resulted in decreased production of some industrial mineral products used in the drilling sector. Trends in mineral-related sectors of the domestic economy declined or held steady, except in the manufacturing of nonmetallic mineral products and nonferrous metals excluding aluminum, which increased. Overall, mining trended downward as the result of significant declines in coal mining, oil and gas extraction and metal mining (Table 2). Discussion of mine production is frequently segmented according to the type of materials produced within the broad categories of metals and industrial minerals (also known as nonmetallic minerals). Industrial minerals can be further subdivided as construction aggregates and other industrial minerals. Metals tend to have higher unit values but very low production quantities compared with those of industrial minerals, which have higher production quantities but are lower-valued materials, such as crushed stone or construction sand and gravel. Therefore, for discussion and analysis of the performance of the nonfuel minerals industry, the value of production is used rather than the tonnage produced. Tonnages of construction aggregates are orders of magnitude larger than those for most other mineral commodities thus making direct compar"

Jan 5, 2017

By E. C. Harder

BRITISH Guiana, Great Britain's only South American colony, may be reached by very comfortable steamers, both from North America and Europe. The trip from North American Atlantic ports requires about 12 to 14 days; that from Europe about 18 to 20 days. A number of steamship lines, including Canadian, American, and Dutch, have regular sailings between North America and British Guiana, with calls en route at various interesting ports in the West Indies and northern South America. Moreover, several lines, including British, German, and French, have steamships operating regularly between Europe and the West Indies. Indeed, so popular have the West Indian voyages become in recent years that, during the winter months, special cruises in considerable number are organized for many vessels that ply in the trans-Atlantic service in the summer. A trip to British Guiana, therefore, has become a delightful experience. After visits at the various attractive Leeward and Windward islands and Trinidad, the approach to the low, flat, British Guiana coast, with its muddy coastal waters extending for many miles offshore, is somewhat of a contrast. Arrival in Guiana waters is signalled by the appearance of the modern high-power Demerara Light, located "on a shoal about twelve miles from the mouth of Demerara river. From this point, if the tide is right, a pilot takes the steamer across the bar, eight to ten miles offshore, and into Georgetown harbour. At high tide, the water above the bar ranges from 15 to 18 feet in depth, depending on whether it is neap tide or spring tide; at low tide, the corresponding depths are 9 to 11 feet. As the bar is of soft mud, however, it is usually possible for vessels to pass over it with a draught of about two feet in excess of that indicated by the tide tables. Upon nearing the shore, one sees first the Georgetown wireless towers, then the light-house and the tall chimneys of sugar mills and of various factories in Georgetown, and finally the palms and other tropical trees and the houses of Georgetown itself along the sea shore and the east bank of Demerara river. Extensive wharves operated by various exporting and importing companies stretch along the river bank and activity prevails in Georgetown harbour. The principal exports are sugar, rice, gold, diamonds, bauxite, balata, lumber, fruit and other tropical products. The imports are food-stuffs, wearing apparel, and manufactured materials of many kinds.

Jan 1, 1936