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By William M. Luff

"The Bathurst area has recorded mining production as early as 1837, although the bulk of the production has come in recent years. Production has been mainly from the well-known massive sulphide deposits, but vein, gossan, and a variety of other deposits have also been mined. This paper summarizes the history of the mined deposits, along with tonnages and grades produced. A number of ""firsts"" have been noted in the Bathurst area. The A Zone deposit, located in the Heath Steele area, was the first in the world discovered using airborne electromagnetic methods. Heap leaching of gold from the gossan zone at Caribou was the first operation of its kind in Canada. The Keymet mine was the first base metal (lead-zinc) mine in New Brunswick. For the past few years, the Brunswick No. 12 mine has been one of the largest zinc mines in the world.IntroductionThe Bathurst area (Fig. 1) first had mining production in 1837 when copper was mined from a deposit on the Nepisiquit river (MacKenzie, 1958). The majority of the production, however, has been in recent years from massive sulphide deposits, but there are also other significant operations. . Table 1 is a summary of Bathurst area mineral production, showing concentrator feed tonnages and mill feed grades. The table does not include peat deposits, sand and gravel, dimension stone or rock quarries. Figure I is a general geology map of the Bathurst area, indicating deposit locations. The deposits are divided into four categories: massive sulphide, vein, gossan and other. The deposits in each category are described in chronological order of exploitation."

Jan 1, 1995

By William M. Luff

"The Bathurst area has recorded mining production as early as 1837, although the bulk of the production has come in recent years. Production has been mainly from the well-known massive sulphide deposits, but vein, gossan, and a variety of other deposits have also been mined. This paper summarizes the history of the mined deposits, along with tonnages and grades produced.A number of ""firsts"" have been noted in the Bathurst area. The A Zone deposit, located in the Heath Steele area, was the first in the world discovered using airborne electromagnetic methods. Heap leaching of gold from the gossan zone at Caribou was the first operation of its kind in Canada. The Keymet mine was the first base metal (lead-zinc) mine in New Brunswick. For the past few years, the Brunswick No. 12 mine has been one of the largest zinc mines in the world.IntroductionThe Bathurst area (Fig. I) first had mining production in 1837 when copper was mined from a deposit on the Nepisiquit river (MacKenzie, 1958). The majority of the production, however, has been in recent years from massive sulphide deposits, but there are also other significant operations.Table I is a summary of Bathurst area mineral production, showing concentrator feed tonnages and mill feed grades. The table does not include peat deposits, sand and gravel, dimension stone or rock quarries. Figure I is a general geology map of the Bathurst area, indicating deposit locations. The deposits are divided into four categories: massive sulphide, vein, gossan and other. The deposits in each category are described in chronological order of exploitation."

Jan 1, 1995

To form a true picture of the early history of Queensland, we must think of white settlement advancing like an incoming tide, wave by wave; each wave lapping ahead a little further than the last. The credit for opening up the country belongs to a large number of pioneers, each of whom pushed out just a little further than his predecessors.Contrary to what one might expect, Rockhampton district was settled by overlanders from the south and not from the ocean side. When the Archers, the pioneers of the Rockhampton district, reached Gracemere in 1853, settlement had already made its way down the valley of the Dawson River; for it was from Leith Hay's station at Rannes (a few miles below Mount Morgan) that the Archers advanced northward into the unknown, to find the river that the explorer, Ludwig Leichhardt, had told them must enter the sea somewhere near the Tropic of Capricorn.The Archers travelled northward from Rannes up the valley of the Dee, coming out on the edge of the Razorback Range not very far from the point at which the Dawson Valley Highway drops over into Poison Creek. (Their diary records the bearings from a lookout point to various peaks around Rockhampton, and to-day, by plotting back from these peaks, we can determine the exact spot at which they descended on to the Fitzroy Flats.) We can be certain, then, that they must have been the first white men to set eyes on Mount Morgan; though to them it would have seemed to be nothing more than an insignificant hill...

Jan 1, 1939

By Robert W. Hunt

THE memorable features of American history have been making fast during the last century, and notably so since 1860; and they are by no means confined to political or to any one branch of scientific development. Of all the industrial arts, none show a greater change or a mightier progress than the Bessemer manufacture. And this year, while we are celebrating the first centennial of our national life, we can also celebrate the first decennial of American Bessemer practice. While not forgetting or undervaluing what has been done in other countries, I have thought that a brief history of the introduction and development of the Pneumatic or Bessemer process in America would be of interest. In 1863 the Kelly Pneumatic Process Company was formed and an arrangement entered into with William Kelly, who had taken out letters-patent of the United States, Nos. 16,444 ; 17,628, re¬issued as 505; 18,910, dated January 10th, 1857 ; June 23d, 1857; November 3d, 1857; and December 22d, 1857, respectively. This association was composed of the Cambria Iron Company, E. B. Ward, Park Brothers & Co., Lyon, Shorb & Co., Z. S. Durfee, and, later, Chouteau, Harrison & Valle joined the combination. Not satisfied with possessing the control of the Kelly patent, they sent Mr. Z. S. Durfee to England, to secure for this country Mushet's patent on recarburization, No. 17,389, dated May 26th, 1857, the same having been taken out in England on September 22d, 1856. In this Mr. Durfee was successful. Previous to the application of William Kelly for a patent, Henry Bessemer, of England, had taken out patents dated February 12th, 1856, and August 25th, 1856, in this country. Kelly claimed priority in the discovery of the principles of the process, and the Patent-office allowed his claim by granting him his patents. In the autumn of 1862 Mr. Alexander L. Holley, while in England, was impressed with the importance of Mr. Bessemer's inven¬tion, and so fully foresaw its future, that, upon his return to the United States, he induced Messrs. John A. Griswold and John F. Winslow, of Troy, New York, to join him in endeavoring to possess Bessemer's American patents. Mr. Holley returned to England in

Jan 1, 1877

By Robert J. Tuchman

This report presents the origins of the Bureau of Mines and the evolution of the Pittsburgh Research Center from its inception to its present form. Areas of major research emphasis over the years, as well as administrative reorganizations, are discussed.

Jan 1, 1998

By Willie M. NeSmith

In the Metropolitan Atlanta Area today, augered, cast-in-place (ACIP) piles will be considered on most projects where deep foundation support is required. ACIP piles were first used in Atlanta in the late 1960s, and application began to blossom in the mid-1980s. Current design practice for ACIP piles is addressed in another paper in this conference. This paper describes the evolution of the ACIP industry in Atlanta, and details the use of ACIP piles on major projects in the Atlanta area.

Jan 1, 2003

By D. J. de Clerk

Global trends stipulate the need to optimize existing assets while reducing environmental impacts. This paper illustrates the procedure that was followed to achieve such goals at one of the coal burning flash dryer units at an Anglo American smelter. An in-depth study of the process and related literature led to the development and installation of a revised control philosophy. This system includes modifications to the existing regulatory control structure as well as a hybrid rule-based and model-predictive advanced process control (APC) layer. Since commissioning of the APC, this flash dryer?s average throughput has increased by more than 6%, despite higher feed moistures. Furthermore, even though coal consumption has increased slightly, operating efficiency has improved by close to 5%. This was made possible by improving stability of the drying column outlet temperature by approximately 40%, which in turn enabled selection of a more optimal setpoint. Recent data has shown that APC utilization now exceeds 95%. This is indicative of a successful controller installation with good site acceptance. The same philosophy has therefore since been rolled out to most of the other flash dryers in the group.

Jan 1, 2012

By Stephen Mansfield, Nathan West, El Khalil Seyed

In October 2017, a multi-bench failure occurred in the east wall of the Guelb Moghrein copper and gold mine in Mauritania. The failure extended 100 m (328 ft) vertically and horizontally and resulted in the sterilisation of ore, but no equipment or personnel were put in danger. The remediation plan successfully removed the failed material and the cutback resumed to a modified pit design, leaving ore reserves behind. In 2021 after completion of mining in another part of the pit, a plan was formulated to develop a narrow cutback behind the failed wall and recover the sterilised ore. Infill drilling defined a resource of approximately 2.9 Mtonne (3.2 Mton) of ore at 0.78% Cu and 0.67 g/t Au at a strip ratio of 5.5:1. The high strip ratio meant that it was necessary to mine thirteen benches of waste, or 156 m (512 ft) vertically, over a two-year period before reaching the first ore, with the cutback only being economically viable if all ore could be depleted at the end of the third year. The high economic risk of the project required a holistic approach to mitigate the risk of another wall failure, by addressing the following areas: 1. Pit Design: with help from an external Geotechnical Consultant, the pit design was optimised to include increased factors of safety, reduced stress points, lower overall slope angles and straight lined walls were replaced with curved walls. 2. Geotechnical Management: the site Geotechnical Superintendent worked closely with an external Geotechnical Consultant to better understand the structural geology. Slope monitoring was improved through an expanded network of prisms, regular in field inspections and the use of a slope monitoring radar. 3. Drill and Blast: new drill and blast designs were developed from first principles, consisting of production, wall control and presplit designs. Blast master polygons and bench development sequences were developed with consideration of the structural geology and the influence of the initiation designs. 4. Mine Operations: improving operational discipline was a critical factor that ensured the accurate execution of drill and blast designs and excavation to bench levels and pit limits. This holistic approach has enabled the safe development of the cutback down to the 936 RL (relative level), two benches below the point at which the previous wall failure occurred. Extraction of ore has occurred from the 960 RL, and due to faster than planned excavation rates, the cutback is expected to be completed ahead of schedule.

Jan 21, 2025

By Nicholas Bonderoff, Amily Xu

The evaluation of battery electric vehicles (BEVs) in underground mines involves comprehensive business case analysis beyond just the capital and operating costs of the equipment itself. BEVs demonstrate benefits from an EHS perspective, reduced mine ventilation costs, lower energy operating costs, reduced overall GHG emissions (dependent on the source of electricity), elimination of DPM, lower equipment maintenance costs, and reduced cooling requirements in deep mines. When including batteries and supporting infrastructure, BEV capital costs are approx. 80% greater than that of diesel equipment. The project economics are highly dependent on the cost of electricity and diesel fuel, and these can vary widely depending on the location of the mining operation. Battery charging and swapping methodologies must be evaluated as there are a variety of approaches that can be employed which vary by manufacturer and type of equipment. Careful consideration of the cycle times, charging methodologies, and location of the battery charging infrastructure is necessary. Specific operating conditions must also be taken into consideration. For example, the time for blast gases to clear will be increased by reducing ventilation flow, and the potential impact on production needs to be evaluated. Similarly, the electrical distribution system needs to be evaluated for peak loading conditions when BEVs are charging. Criteria including maintainability, reliability, commercial availability, and performance need to be evaluated. BEVs have fewer components than diesel equipment and this correlates to lower overall maintenance costs, however, BEVs require maintenance personnel with specific skill sets in order to maintain the equipment. Battery lifecycle costs need to be considered as battery replacement incurs significant capital expense. Some manufacturers offer services to offset these capital costs through usage agreements. Recycling and disposal of batteries at the end of their lifecycles also need to be considered. With the increased selection of BEV equipment that will be available in the next 2-4 years, 100% BEV adoption is also possible. We recommend a holistic approach when evaluating BEVs for underground mines. This will ensure that everything is considered in order to evaluate the full impact of BEV implementation.

Jan 1, 2023

By D Genge, E Martin, T Goswami, M Rothery

Rio Tinto’s Hunter Valley Operations is a large open pit coalmine situated in the heart of the Hunter Valley in Australia. The Riverview West Pit has faced increasing production challenges in recent times due to decreasing dragline strike lengths and increasing environmental constraints on vibration, overpressure and fume generation. Conventional mining techniques would involve five to six production blasts per strip to recover multiple coal seams. Each blast event carries the risk of exceeding the strict environmental requirements. By working collaboratively with Orica, it was realised that the blasting method known as Stratablast™, in conjunction with advanced computer modelling techniques, could provide productivity gains whilst simultaneously providing more control over the environmental effects and the impact on nearby infrastructure.As a result of this change, the number of blasts per strip was reduced to one, with the implication that a great deal of care and forethought was needed to manage the increased challenge posed by multiple constraints in the proposed mining area. This innovative approach of combining throw and stand-up blasts allowed the extraction of all major coal seams in a single pass blast event. The blasts were initially designed with a large factor of safety to stay within environmental limits as they were over 1.1 km in strike length, with more than 800 holes and with a total charge weight of about 1000 t of bulk explosives. Furthermore, there were conflicting priorities around the desired blast outcomes. So far, 11 such blasts have been designed and successfully fired. After each blast, innovative design changes have been iteratively implemented to provide further control over environmental impacts, whilst continuing to improve productivity. As a result of these changes, blasts have progressively increased in complexity with the inclusion of features such as damage zones, mid-splitting, time gaps and different directions of firing. The consequence of this complexity is that the blast duration can be as long as 28 seconds to accommodate all components of the blast.This project has increased the productivity of the Riverview West Pit through blast design improvements and allowed the environmental impacts to be managed with far more control and predictability than would have been possible under a conventional blasting regime. There still remains room for further optimisation of mine productivity and this is being addressed through a process of continuous improvement.CITATION:Goswami, T, Martin, E, Rothery, M and Genge, D, 2015. A holistic approach to managing blast outcomes, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 645–654 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Tom BoBo, Seth Gering, Jeff Loeb

Presenting a D&B feedback loop built on a well-designed blast, proven fragmentation analysis and blast monitoring solutions, underpinned by technology that not only increases profit from every blast, but also increases a mine’s purchasing power over one of the most expensive part of the process – explosives.

Feb 1, 2020

By Tom Barry, Kameron Ray, Dr. Gavin Yuill

Imerys Talc, Yellowstone Mine in Montana faces significant geotechnical challenges such as poor wall quality and local instabilities. These instabilities are driven primarily by the characteristics of the rock mass, but are aggravated by drilling and blasting operations.

Jan 1, 2016

By K. Sample

Slope stability analysis plays an integral role in the design of various mining applications including waste dumps, heap leach piles, solution ponds, and tailings dams. Generally, limit equilibrium analysis using one of the several prevalent approaches is considered adequate. The density, saturation, and shear strength parameters of the materials forming the slope affect the failure mode and the calculated factor of safety (FS) against sliding. These parameters are generally based on laboratory tests. Field practices and construction procedures are often not completely simulated in the laboratory for various reasons (e.g. equipment limits, time and budget restraints, etc.). This paper presents a holistic assessment of slope stability analysis as practiced in mining applications, using example data from multiple heap leach projects. A sensitivity analysis is presented for variations in material properties, data interpretation, and computation methods. For each step in the design process, the possible variations in parameter values were identified and then used to perform traditional and probabilistic stability analyses. This simple, cradle-to-grave-type approach is used to evaluate the reliability of an example design, and the combined impact of multiple uncertainties on the factor of safety. Example Study The issue of addressing uncertainty in geotechnical design has been discussed in depth by numerous authors (Duncan 2000; Christian 2004; Whitman 1984; Christian et al. 1993). One may ignore the uncertainties involved in a design, take a conservative approach, rely on observational methods (Peck 1969), or attempt to quantify the uncertainty. Geotechnical projects in general, may include a combination of these methods. For important structures, such as heap leach pads, it is critical that sources of uncertainty in the stability analysis be acknowledged early on and considered in the overall design approach. As with any project, economics and other physical constraints, such as space limitation, often do not always allow for an overly-conservative, robust design. In an effort to quantify uncertainty and provide a sense of level of confidence in the safety and reliability of a design, probabilistic methods have been developed and implemented in many slope stability software packages. Reliability methods are often used in the design of open pit mine slopes, but not as commonly in designing heap leach pads and waste dumps. As an example, the stability analysis of a copper heap leach project is presented here to evaluate the effects of multiple sources of uncertainty and differing methods of data interpretation. Some of the parametric values, or the variation therein, are assumed on the basis of actual data from multiple heap leach projects, included in the paper as well. A generic representation of the example case study is shown in Figure 1. As depicted in the cross-section, the ultimate height of the design is 114 m (measured from the crest to the toe). The overall slope of the heap leach pad is 1.88 horizontal to 1 vertical (1.88H:1V), or 28°. The slope benches are considered in the overall slope. The example leach pad is founded on alluvial, colluvial and residual soils overlying weathered limestone. The ore to be placed on the pad is characterized as poorly graded gravel (GP) with average fines content (percent passing #200 sieve) of 4%. The liner subgrade is low permeability (fine) soil. The cover or the drainage material, placed directly above the geomembrane (between the liner and the ore), is crushed ore in this case. The phreatic surface was assumed to be 1 m above the base liner, which is what the collection system over the liner is typically designed for. [ ] In heap leach pads, typically, Linear Low Density Polyethylene (LLDPE) or High Density Polyethylene (HDPE) is used as the base liner. The decision is based on the elongation, strength and other requirements of the application as well as economic considerations. In this example study, the base liner was 80-mil single-side textured LLDPE. FIELD INVETIGATION AND SAMPLING When selecting appropriate values for the input parameters of the stability analysis, the level of uncertainty in the data and the assumptions that are made must be clearly identified and considered in the design. This concept has been emphasized through an extensive number of publications regarding geotechnical uncertainty and reliability (Christian et al. 1994; Duncan 2000; Christian 2004). The primary source of uncertainties involved in slope stability analysis for mining applications is inadequate geotechnical investigation, often lacking in a thorough assessment of in-situ material characterization and sampling disturbances. To emphasize this point, some background information is presented here. The tradeoff between the costs of a thorough site investigation versus the risks of design uncertainty has long been a challenging management decision in geotechnical projects. For mine sites, significant investment is typically made in exploration and estimating mineral resources and the geology of a mine site is often more thoroughly documented than other types of geotechnical projects. Nevertheless, the engineering properties of the soil and rocks relevant to slope stability receive less emphasis. Baecher and Christian (2003) observed that the areas of geotechnical concern, such as slopes and waste disposal facilities, are usually associated with mine costs rather than revenue, and therefore, significantly less money is devoted to their site characterization and laboratory testing. The expenditure for site investigations varies significantly from project to project, with higher levels of uncertainty and, therefore, the

Jan 1, 2009

By Russell C. Frith

This paper examines the design of longwall shields, focusing on those aspects that are critical to either their successful application or contribution to failure during longwall extraction. In many instances, longwall shields are assessed and designed along lines similar to that of roadway ground support systems, namely according to typical or normal geotechnical conditions. However it will be contended that for longwall shields, this is inappropriate because unlike roadway ground support systems, longwall shields cannot be supplemented with additional or secondary support in localised areas of adverse geotechnical conditions. In other words, the longwall shield needs to be designed according to what are judged to be worst case or adverse geotechnical conditions?the outcome being that a well-designed shield will be significantly over-rated for the majority of its working life. Therefore, it will be argued that the additional capital cost of such shield design can be readily justified as a prudent riskbased outcome that is essential to minimising future business risks due to strata instability on the longwall face. Shield geometry will be discussed, including such relevant factors as leg angle, inclination of the top caving shield, canopy ratio, operating height range, and tip to face distance. These are all well-established longwall shield design considerations and, most importantly, areas whereby inadequate design can render a longwall shield as highly ineffective. The issue of tip to face distance will be considered in detail, in particular, the extent by which it is an important geotechnical design consideration, the conclusion being reached that, in fact, it is not. The critical importance of maximising set to yield ratio within practical operating limits will be justified, the wisdom of this having been subject to questioning in more recent technical literature. Overall, the aim is to provide the industry with a set of suggested guidelines for future use when designing longwall shields and, hopefully, to initiate discussion on a subject that, unlike roadway ground support design, is not well covered in its entirety in the published technical literature.

Jan 1, 2013

By R M. Krek

The haulage system used to convey ore from an underground mine to a surface stockpile at the mine process plant is a vital component of the mine’s overall infrastructure and economic viability. The system selected has a significant impact on the set-up of the mine and the access to the underground mine. In turn, the set-up of the mine and the access to the underground mine have a significant impact on the system.A number of haulage technologies are available to transfer the ore from the underground workings to the surface stockpile, including hoists, conveyors, rail and trucks.This paper focuses on the shaft hoisting and inclined conveyor haulage technologies. These technologies have been used consistently to deliver ore from at depth and/or at high tonnage. Previous reviews of the appropriate vertical haulage systems have nominally been restricted to the respective systems only, with no consideration for any other scope or issues that may affect the selection. The selection of the appropriate vertical haulage system, whether shaft hoisting or inclined conveying, needs to consider numerous key factors.CITATION:Krek, R M and Northcote, A E A, 2014. A holistic viewpoint for selecting the vertical haulage system – shafts and conveyors, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 289–296 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By H Arvidson, Rondinelli Sousa, Nic Pollock, Cesar Carrasco, Boz Elloy

Global public mineral reporting codes have driven strong governance of public disclosures of minerals information. Recently, we have seen an increase in disclosure of information related to Environmental, Social and Governance (ESG) issues, and governance of ESG information in mining companies has arguably reached a similar level of governance and diligence afforded mineral reporting. We define Resource Governance as the conjunction of environmental, social and minerals governance. A modern systems approach to Resource Governance, which combines mineral and ESG information, would provide not only reporting and governance capability, but also has the potential to sense/respond, predict, and manage ESG risks.

Feb 1, 2024

By V. Labiouse, F. Orellana

"Hollow cylinder samples can be tested for both the characterization of rock properties and the physical modelling at reduced scale of engineering applications. Particularly, this type of experimental setup can be used to simulate different stress conditions around underground openings, as already developed in the petroleum engineering field e.g. to study the instabilities around deep wellbores during either drilling or the oil production phase. Some authors have also used this technique to successfully characterize the damaged zone around underground openings in the tunneling engineering field looking for an efficient design of their support.This article presents a new hollow cylinder testing device developed at the Rock Mechanics Laboratory of the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland. It allows a full and independent control of the confining pressure and pore water pressure conditions at both the inner and outer boundaries of Thick-Walled Hollow Cylindrical samples. In order to mimicking a tunnel excavation in a porous rock mass, after initial recovery of the in-situ stress and pore water pressure, the hollow cylinders are subjected to a decrease in the internal confining pressure. Moreover, X-Ray Computed Tomography scans of the specimens are performed through the testing cell before and after the mechanical unloading to monitor the displacements undergone and the sample damage. The equipment, testing procedure and data analysis techniques are briefly presented in the paper.The good performance of the apparatus has already been checked on weak rock specimens, among others on Boom and Opalinus Clay samples. In many configurations, the mechanical unloading is found to induce a Damaged Zone (DZ) around the central hole. Its geometry and extent show a great similarity with in-situ observations around tunnels driven in the Boom and Opalinus Clay formations. Such similarities contribute to increase confidence in the understanding and modelling of the ongoing processes."

Jan 1, 2015

By James P. Sloss

A PERMANENT assay office is commonly established as part of the general plant equipment of operating gold and silver properties, but during the development stage of a mine, the cost of such an office is usually so assay work must be done elsewhere. In most instances only a few samples will be taken each day, but if the mine is to be developed scientifically, the analyses of those samples will guide further development. Under such circumstances, the time element in assay returns is important, since the lapse between the taking of the samples and the receipt of results may determine the success or failure of a small-mine operator. The following description of fur-

Jan 1, 1935

By A. J. Pearce

MOST mines have a model of some kind to illustrate either geological structure, mining operation, or some special condition or feature of the property. The type used depends on the particular feature or use for which it is intended. At Dome Mines we have developed an interesting and practical application of the horizontal-type model. This model shows the workings of each level horizon plotted on glass. These glass panes are set in frames which, in turn, rest on drawers equipped with rollers which can be pulled out as desired into a light chamber. The features of this model are its rigid steel construction and that any desired number of level plans can be pulled out, eliminating any other interference from other levels. Figures 1 and 2 are photographs of the model cabinet and show its construction and general features. The cabinet is of steel construction with the following overall dimensions: width, 6 ft. 5 in.; depth, 6 ft. 7 in.; height, 5 ft. 2 in. When not in use it can be completely closed-in, making the cabinet practically dustproof. There are 30 drawers, one for each of the 29 levels and one for the surface. The glass in each drawer is divided into two panes, 36 in. by 36 in., of flatdrawn double-diamond 'lustraglass' with about l/32 in. between adjacent edges. The panes are held rigidly in the frames, which are lined with felt strips, and may be adjusted by set screws, four of which on each drawer are shown in Figures 1 and 2. The level workings, on a scale of 1 inch equals 100 feet, are traced in ivory black Windsor & Newtons artist oil paint. Co-ordinate lines are shown in crimson lake, and main geological contacts are shown in their respective colours. Figure 3 is a photograph looking down on one of the levels. The lighting consists of 14 30-watt fluorescent bulbs, with reflectors, under frosted glass. These lamps are much more satisfactory when operated by 60-cycle rather than 25-cycle and, as we had available nearby a source of direct current, this was used. The electrical unit consists of a rotary converter from d.c. to 60-cycle. This arrangement gives perfect lighting, allowing most colours to be easily distinguished. Figure 1 was photographed using this source of light, Figure 2 using an outside floodlight.

Jan 1, 1945

By T. S. Taylor

THE development of the linear hot-wire anemometer has been chiefly clue to the efforts of L. V. Kings1 and A. E. Kennelly and H. S. Sanborn.2 The anemometers used by these investigators consisted essentially of a fine heating wire having attached leads for resistance measurements at distances of 10 or more centimeters from each other. In using such an anemometer, the current is measured that is necessary to maintain the resistance of the wire, between the two leads, constant for different air velocities. Thus resistance is always so chosen that the temperature of the heating wire will be sufficiently high to make the observations practically independent of small variations in the temperature of the gas in which the anemometer is placed. The measurement of the resistance of the anemometer wire requires a Kelvin bridge set up, which for commercial work is not altogether desirable. The cooling effect clue to different air velocities depends on the temperature difference between the wire and the gas and the total quantity or mass of gas passing the wire per unit tine. Since the temperature of the wire is maintained constant, the effect observed in the change in the heating currentfor a given change in air velocity is a measure of the difference between the gas flow in the two cases. Such an anemometer, therefore, measures the average gas flow for a length depending on the distance between the two resistance leads. Therefore the instrument in the form used thus far is not very satisfactory for measuring gas velocities in small tubes or in places where the velocity varies rapidly across the line of flow. For the purpose of measuring gas flow through relatively small tubes, where the velocity changes rather rapidly across the tube, the hot-wire anemometer has been modified in the manner shown diagrammatically in Fig. 1. It consists essentially of a platinum heating wire H about 0.007 in. (0.178 mm.) in diameter and ½ to 1 in. (12.7 to 25.4 mm.) long stretched across a suitable framework, say of glass. This wire has

Jan 9, 1919