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By R. A. Wharton, Z. Yang, R. W. Smith

The electrokinetic and flotation behavior of the green alga Chlorella vulgaris was studied in the absence and presence of Pb(II), Al(III) and flotation collectors. It was found that the presence of Al(III) is necessary for good flotation of the organism, whether or not Pb(II) is present, when dodecylammonium chloride or sodium dodecylsulfate is used as collector. Best flotation using dodecylamine is at about pH 8, and best flotation when using sodium dodecylsulfate is at about pH 4. It appears because of the small size of the organisms that the Al(III) is necessary for flocculation to enhance bubble-cell contact and C. vulgaris removal from water. When N-dodecyl-2-aminopropionic acid is used as collector, good flotation occurs at about pH 4 without the addition of Al(III).

Jan 1, 1992

By R. J. Haydel

The Highland Uranium Operations of Exxon Company, U.S.A. is a large uranium mining and processing complex situated in the Powder River Basin of East-central Wyoming. Surface mining and chemical processing of a large relatively low-grade ore body began in late 1972. An underground mine was later developed and began production in November of 1977. Figure 1 shows the location of our operations. During the planning stages of the project, it was recognized that hiring and retaining quality employees would be a significant problem. Other operations in similarly isolated locations were experiencing high turnover rates and were forced to employ inexperienced and poorly trained operators. In an attempt to attract employees, many of the companies provided mobile home or bunk- house facilities, but these costly peripheral ventures did not prove to be noticeably successful.

Jan 1, 1979

By D. R. Nagaraj

Literally thousands of new flotation agents, both collectors and modifiers, have been proposed for sulfide and non-sulfide flotation over the past six decades since the beginning of the use of soluble surfactants in flotation. In stark contrast, the number of flotation agents used in practice is small. Xanthates and fatly acids, along with a few well-recognized modifiers, dominate the industry. Three major questions will then arise: a) are there truly specific needs in the industry that call for chemistries that are different from those used currently ? b) if yes, given the track record in the industry, what is the likelihood that such different chemistries will ever be used and to what extent ? and c) is more research into developing new chemistries necessary ? A critical assessment of flotation agents in general is made in this paper to provide answers to these questions and to identify the major factors that are responsible for the large disparity that exists between flotation reagent research and commercial usage.

Jan 1, 1994

By Robert T. Chapman

Many of us are privileged in that we have witnessed the transition from mining methods used in the first quarter of the twentieth' century to those practiced today. In the late Twenties, for example, many mines still used hand mucking methods. In the middle Thirties, more than one large metallurgical limestone quarry still used the 4 cubic yard railway steam shovel formerly in use at the Panama Canal. Mules could occasionally still be found underground, where they provided the-main-source of motive power. Within the last decade, and even within the past five years or less, great improvements have been made in blast-hole drilling, ore loading, and ore hauling equipment. Industrial demand for minerals can be expressed in exponential terms as compared to that at the turn of the century. Even marine mineral resources are receiving accelerated attention. One overall result is that larger and lower grade orebodies can be exploited at a profit. This profit must be made despite, for example, a static monetary price for gold, and despite the continual cost escalation involving labor, materials, supplies, and equipment. Accordingly, the application of the necessary degree of knowledge and judgment required to meet production, cost, and profit goals is paramount.

Jan 1, 1966

By William F. Jenks

The possibility that a hypothesis explains almost all observed facts may be satisfying. Yet the almost gives a distinct sense of uncertainty. Moreover, overlooking the almost, reliance on the favored hypothesis may close our eyes to the discovery of new information and, in the field of mineral exploration, to the possibilities of finding new and hidden ores. A case in point is that of mines such as the Elizabeth and Ely, along the copper belt in eastern Vermont, principally in Orange County. The geology of the Strafford Quadrangle, where the Elizabeth Mine is located, has been described by Doll (1944). Two informative papers (McKinstry and Mikkola, 1954, Howard, 1959) present much valuable information about the geology of the Elizabeth Mine. Both reach the conclusion that the ores were emplaced after the peak of metamorphism, through the agency of metal-bearing hydrothermal solutions. Both, therefore, conclude that the source of the ores was somewhere below the outcrop area, presumably in some hidden intrusive mass. Neither yields a satisfactory guide for further exploration. Howard (1959) cites geophysical observations which show that there is a mass with a density similar to that of granite under the Strafford dome, adjacent to the Elizabeth Mine on the West. Yet examination of gneissic granite in the Chester dome, 25 miles to the South gives no suggestion of a young, near-surface intrusive capable of carrying or mobilizing large quantities of sulfur and metals. The Acadian intrusives in New Hampshire and in the Barre district

Jan 1, 1968

By Guoqing Li, Hao Wang, Nailian Hu, Victor Tenorio, Jie Hou

This paper presents an algorithm for optimizing the scheduling of trackless equipment in underground mines. With the shortest working interval and maximum productivity as goals, a genetic algorithm (GA) is used to solve the problem, and obtain the optimal working sequence with the most suitable equipment configuration possible. The input for the proposed method is the number of units and capacity of trackless equipment, the production process, ore amount in stopes, and the distance between stopes. The algorithmis verified using four setups of 5 stopes with 5 cycles, 5 stopes with 15 cycles, 10 stopes with 10 cycles, and 10 stopes with 30 cycles. The solution time of the algorithmis no more than 20 min, which is acceptable for practical applications. The results show that the setup of 10 stopes with 30 cycles is closer to the actual production of the mines, and the optimization model can effectively improve the operation efficiency. In this scenario, the robustness of the optimization is tested by simulating equipment failure events. Under the condition of 8% failure rate, the operation time is extended over 3.21–14.56% than expected, which represents strong robustness. The algorithm can quickly provide a feasible and effective solution for the production scheduling decision of trackless equipment in underground mines.

Aug 12, 2020

By A. A. Jonke

The combustion of fossil fuels in a fluidized bed of calcined limestone particles is a potentially efficient and economically attractive process for the generation of steam for electric power production and other uses. The process results in greatly reduced emissions of both sulfur oxide and nitrogen oxide pollutants. Development work, evaluations and design studies are being carried out by various organizations under contract with the U. S. Environmental Protection Agency and the Dept. of Interior (Office of Coal Research). The AEC's Argonne National Laboratory is one of the principal participants in the development program under interagency agreements with EPA and OCR. This paper covers the principal reasons for developing fluidized-bed combustion, its advantages and disadvantages over conventional combustion methods, and some of the potential applications of the process. The participants in the multi-organizational program, the sponsoring agencies, the general status of development of the overall project, and the chief program areas that still require resolution are discussed. The main features of the program of work at Argonne National Laboratory and the results achieved so far are also included.

Jan 1, 1974

By Claudia Castillo, Katja Freitag, Jan Cilliers, Diana Drinkwater, Robert Seitz

The talent gap in mining is not a new challenge. Mining companies continue to seek innovative ways to attract, develop and retain talent, and younger workers are looking for opportunities to develop their professional careers. Training provides a key value proposition for both employees and employers as it helps build a talent pipeline while offering opportunities for learning and growth and value creation. In 2020, Metcelerate launched its 20-month program for early career mineral processing engineers. The program helps develop critical technical skills in the workplace and is a tool to identify motivated engineers and change culture within teams. Learners cap their skills development by executing a technical investigation. This generates immediate value—a win-win outcome for learner and company.

Feb 1, 2025

By B. S. Crocker

Introduction Pebble mill grinding can be defined as wet or dry grinding in a tumbling mill with pebbles used as grinding media instead of metal balls. To clarify the terminology, which may differ in the various mineral industries, it is essential to point out the differences between grinding with partially sized and carefully sized grinding media. When grinding with partially sized media (limited top size only), sizing is usually the setting of the primary crusher and there is no bottom sizing-all fines, chips, sand, and small sizes are included. This is often called run-of-mine or primary autogenous grinding. In this case the entire crusher discharge is fed into the mill and part of it becomes "charge" and the rest is "sand feed." When grinding with carefully sized media (i.e., media that is sized both at the top and bottom of the size range), no fines or chips should be present in the charge to the mill. This is pebble milling and the grinding media consists of ore, rock, Danish pebbles, gravel pebbles, or ceramic pebbles-media that is appreciably lighter than steel balls. The grind¬ing charge is fed to the mill to maintain a load and it does the grinding usually on a classified sand product of suitable size. If the grinding media is the same as the raw material being ground, this type of grinding is also called secondary autogenous grinding. Pebble milling was in common use in the gold mines of South Africa in the early 1900s. It is by far the oldest form of autogenous grinding. It may be used to grind crushed ores from a maximum size of about -% in. to all -10 µm. Pebble milling differs from "run of mine" grinding in many ways, but two big differences are: I) The ore itself is crushed to approximately t/4 in., or it may be further reduced to 8 or 10 mesh in a rod mill or fine crusher. 2) Then carefully screened ore of the correct size is placed in one or more stages of pebble mills to grind the ore to its desired final size. The media size is carefully selected to be the most efficient for the particular size reduction required in each stage. This is a precise practice, and pebble mills can be designed as easily and accu¬rately as can rod mills or ball mills by those skilled in the art. A pebble mill is a rotating cylinder in which the grinding media has been carefully sized for the job in hand. If the mill is doing coarse grinding, the media will be correspondingly large and the mill might be called a primary (or intermediate) pebble mill or a lump mill. If it is to do fine grinding, the media selected is proportionately smaller and the mill would be called a secondary or tertiary pebble mill. The media itself is normally rounded pebbles made from screened ore from the primary-crusher discharge. The charge could be rounded pebbles of the correct size removed from a primary autogenous mill, or the pebbles could be carefully sized gravel, sized beach pebbles, or sized flint pebbles. Usually the specific gravity of a pebble is from 35 to 55% of that of steel balls. It commonly varies from 2.66 to 4.2, depending on the specific gravity of the ore. Primary pebble mills, or lump mills, would be charged with pieces of rock up to 10 in. maximum and 5 in. minimum and would grind crusher discharge with a maximum size of 1/4 in. on hard ores and 3/8 in. on softer ores. Secondary pebble mills could be charged with pieces of rock screened on 4 x 4-in. square mesh and retained on 1 1/2 x 1 1/2 in. These mills would grind material with a top size of 8 to 10 mesh. Tertiary pebble mills could be charged with screened rock that would pass 3 x 3 in. and be retained on 1 x 1 in. and grind 35 to 48 mesh sands. Principles of Operation Media Size To operate a pebble mill efficiently it is imperative that great care be taken in screening the rock feed that is fed into the mill to round up into a range of pebble sizes that are suitable for grinding of the sands that are also being fed into the mill, having regard to the top size and the average size of such sands. Since most mill operators know from experience the correct size of steel balls to be used in a mill to handle different sizes of sand feed, it is convenient to relate the pebble size to a ball size. If the correct ball size is not known, it is relatively simple to conduct batch laboratory tests in 12- to 18-in. laboratory mills to determine the optimum size of steel ball. Also, Bond and others have published formulas for calculating the optimum ball size. When the correct size of the individual steel ball is known, then a pebble of the same weight will perform the same grinding if used in the proper size of mill and under the proper conditions, which will be defined later. This media size, as defined by the average weight of the individual pieces, is most important. The following tests will serve to clarify this point. Laboratory Tests Using Steel Balls or Pebbles. Several labora¬tory grinds were made to compare a given size and weight of steel ball with a pebble of the same weight but larger size, and of the same size but lighter weight. The following loads were used in the 12-in. laboratory mill: All 1 1/4-in. steel balls weighing 122 ± 10 g. All 1 3/4-in. pebbles weighing 123 ± 5 g. All 1 1/4-in. pebbles weighing 45 ± 3 g. To equalize capacity, the test with the steel balls was run only 34% as long as the tests with pebbles. In each case, 2,500 g of primary sands were ground at the optimum gravity for the media being tested at a speed 78 1/2 % of critical speed, and for 170, 340, and 680 revolu¬tions for the steel balls, and 500, 1,000, and 2,000 revolutions for the pebbles. The first test is summarized in Table 74 by showing the 80% passing size in microns for the feed and for each of the grinds. Two other tests are summarized in Table 75 showing the screen analyses

Jan 1, 1985

By William Gleason

While a fleet of 100 t (110 st) haul trucks were busy removing overburden from the open pit mine in the distance, a host of dignitaries, including congressmen and California state representatives, gathered for Molycorp?s official groundbreaking ceremony at the Mountain Pass Mine on April 20. The mine, recognized as arguably one of the richest rare earths deposits in the world, is at the center of Molycorps? strategic ?Mine to Magnets? plan. It aims to secure America?s future supply of rare-earth-dependent technologies by developing a strong domestic rare earth industry. Molycorp identifies rare-earth-dependent technologies as those that cannot be produced without rare earth materials. The list of these technologies is long and growing. It encompasses everything from personal electronics and batteries for hybrid cars to permanent magnet generator wind turbines and national defense applications.

Jan 1, 2011

By Raj K. Rajamani

In ball milling the rates of breakage vary primarily with the size distribution of powder in the mill. In wet grinding viscosity of the slurry varies continually as size distribution changes and hence the breakage rates change. In this study a simpler estimation scheme is used to determine breakage rates in batch grinding. Using an approximate solution to the batch grinding equation, acceleration and deceleration of breakage rates of all individual size classes is determined when the grinding environment is varied. Experimental results with limestone and copper ore show time-dependent breakage rates under both dry and wet grinding conditions. In general the breakage rates increase for coarse sizes and decrease for fine sizes with increase in the fines present in the mill. Such variations have strong implications in closed-circuit grinding.

Jan 1, 1991

By Elizabeth Anne Semon

The marketability of a large volume bulk material is significantly effected by transportation costs. Hence, it is essential for anyone that deals with minerals or mineral wastes to be able to reliably estimate bulk transport costs. The three types of bulk overland transportation modes that will be discussed are truck, railroad, and pipeline. Contract and private carriage are the two types of truck transport generally suitable for movement of bulk commodities. Contract carriers are those transportation firms that service a limited number of shippers and geographic points, and carry a restricted number of commodities. Private carriage consists of control over drivers and equipment by the shipper, ownership or lease of the transport equipment, and shipment of commodities related to the primary business of the shipper.1 A combination of private and contract carriage may also be used. Depending on the size and regularity of the shipment, rail offers single car, multiple car, or unit train service to move bulk minerals. Both long and short distance pipeline transportation has been shown economically and technically feasible for many different solids such as, mine and quarry products, coal, chemicals, copper concentrates, phosphate rock, and sewage sludge. 2

Jan 1, 1973

By George R. Mitchell

It is a common observation that objects having, different; temperatures exchange energy by radiative transfer. The quantity of radiant energy emitted by an object is a definite function of its temperature. Therefore, a measurement of emitted radiation, by means of a calibrated radiometric instrument, provides a temperature measurement without contacting the emitting object. The physical laws describing radiant energy transfer and their application to remote temperature measurement form the substance of this paper. The energy radiated by bodies having temperatures up to 4000°C is largely in the infrared spectral region. The infrared spectral region is that part of the electro-magnetic spectrum having wavelengths longer than visible light and extending to the microwave region. The wave-lengths range from 0.7 micron (1 micron = 10-4 cm) to 1000 microns. In general, infrared radiometry deals, with the methods of measuring energy flux in the 1 to 15 micron region of the infrared spectrum.

Jan 1, 1960

By Alexandru Corneliu Stematiu, Catalin Popescu, Radu Sarghiuta

"The tunnel sector is excavated into a rock mass heavily affected by tectonics, defined as a regional fault. The rock around the tunnel support undertakes the non – elastic deformation and gradually detaches from the rest of the non affected rock mass, moving inside of the excavated area and tending to fill up the whole space. The initial solution of using stiff support consisting in double steel ribs I12 with circular shape in the upper part and straight vertical pillars in the lower part has proved to be inadequate. Based on the calculations of the subsidence phenomena and a mathematical model, the proposed alternative support was provided by special circular steel ribs – SG-23 –that allows a limited rib deformation (by relative slip between the arch segments) in order to mobilize the contact between the rock contour and the inner face of the rib - not only for the deformed rib but also for the neighboring ribs. 1. INTRODUCTION Hydropower development of Jiu river in Romania, in the narrow gorge sector includes two diversion HPP and a small hydro plant that provides the minimum required flow downstream: CHE Dumitra , CHE Bumbesti and MHC Livezeni (Table 1. Hydropower parameters).The Livezeni intake reservoir is provided by a gated dam located 1250 m downstream of merging point between Jiul de Vest river and Jiul de Est river. The dam is equipped with three radial gates with flap gates with a span of 12 m each and the height of (6 + 3) m. The longitudinal profile of Dumitra head and the location of the gallery zone that is the subject of the paper are presented in Figure 2. Longitudinal Profile – Dumitra Head."

Jan 1, 2016

By Danforth R. Hale

The pressure of military use of quartz resonators led to efforts to Grow high, grade quartz crystals in Germany and in Great Britain during 19)3-25, and was responsible for a series of U.S.A. Signal Corps contracts beginning in 1946 with the Clevite Corporation (as the former Brush Development Company), Bell Telephone Laboratories, Antich College, and others. The technique of growing crystals from the melt, such as KI, NaBr, was already commercially inuse Quartz could not be so grown, since its utility depends on the form stable below 573°C, and, even if it could be grown from an extraordinarily viscous melt, the higher form passing through this transition becomes twinned. Again, several crystals were being grown commercially from water solutions; quartz, however, is listed in the common literature as being insoluble in water. Fused quartz, or vitreous silica, was chosen as raw mater¬ial by the European experimenters because of its thermodynamically lesser stability than quartz, and various alkaline solutions were tried for the purpose of enhancing the solubility.

Jan 1, 1964

"INTRODUCTION Foam, unless intentionally created, in any industrial process presents operational problems, or at a minimum, is a nuisance. Some foam problems are unique to a given industry and others are common across many industries. A few problems foam presents to any particular industry are: (a) Poor Housekeeping, (b) Environmental impact, (c) Safety Hazards, (d) Slower Production Rates and, (e) Reduced quality of the end product. Defoamers address these issues. Sadly, the assumption in most industries is all defoamers are alike. In reality, a lot of chemistry is involved in the manufacture of even the simplest defoamer sold today and rarely are any two defoamers “just alike”. Today’s defoamers can include polymer chemistry, fatty esters, alkoxylated alcohols, silicone chemistry, silicone surfactants, ethoxylated and propoxylated block polymers, and a tremendous amount of emulsion chemistry just to name a few. This paper will discuss the various types of defoamers, defoaming mechanisms, the advantages and disadvantages of defoamer selections, and how to choose the proper defoamer for your application. Before a discussion of defoamer can be brought about, foam generation and composition must be discussed. WHAT IS FOAM? Foam is a colloidal suspension of a gas dispersed in a liquid. Most often foam consists of air dispersed in water. If a stream of air is introduced into a liquid, the bubbles produced assume a spherical shape. As the density of the bubble is less than the liquid the bubble rises. When the individual bubbles reach and pass through a surfactant free liquid they collapse. Air from the bubble dissipates and the liquid previously surrounding the bubble flows back.It should be noted a pure liquid will not foam. In the case of air dispersed in water a surfactant is necessary to make the water support a stable foam. A surfactant is a term used to describe a surface active agent; a compound with a hydrophilic end and a hydrophobic end on the same molecule."

Jan 1, 2016

By Edward J. Harvey

Joplin, one of the most famous zinc mining camps of a bygone era, is today experiencing a healthy growth in manufacturing enterprises. Manufacturing requires water, and knowledge of its availability and quality often is the main factor in location of industry. For this reason in January 1964, on the suggestion of the former State Geologist, Dr. Thomas R. Beveridge, a study of the water resources of the Joplin District was undertaken as a cooperative effort of the Missouri Geological Survey and Water Resources now under the direction of Dr. William C. Hayes and the U. S. Geological Survey. The project area is in southwestern Missouri on the Springfield Plateau and is bordered on the west and north by the Osage Plains of Kansas and Western Missouri, (fig. l). Upland altitudes rise from 900 feet above sea level in the west to 1400 feet in the east. The countryside is rolling to moderately hilly and much is excellent farmland.

Jan 1, 1965

By William R. Henkle

High-calcium limestone has been intermittently produced from the Monarch quarry since the late 1800s. Initial production was used in sugar processing and for a smelter located near Salida, Colorado. During the 1920s, Colorado Fuel and Iron Company (CF&I) began to exploit the deposit as a source of flux stone for its blast furnace steel operations at Pueblo. The deposit was operated for many years as a captive quarry by CF&I. In 1984, CF&I closed the quarrying operations at Monarch; flux stone was no longer required since the blast furnaces were taken off line in 198 1. In 1994, Colorado Lime Company, a subsidiary of United States Lime and Minerals, Inc. acquired the property. Limestone was mined from the Castle Butte Member of the Leadville Limestone (Lower Missippian). Some high- magnesium dolomite was also mined during WWII from the Redcliff Dolomite Member which directly underlies the Castle Butte. Past production was from both an upper and lower quarry at elevations ranging from 10,000 to 11,000 feet (3,048 m-3,353 m) mean sea level (m.s.1.). The reserves at Monarch quarry are in a dip slope deposit, occupying the northwest slope of Monarch Hill. The structural geology of the deposit is complex on both a region- al and mine scale. The reserves are located on the eastern limb of the Syncline Hill syncline. The beds on this limb of the structure strike to the northeast and dip to the northwest from 30 to 45 degrees. A major reverse fault separates the reserves into an upper and lower deposit. Numerous smaller normal and reverse faults cut the deposit, requiring a flexible mine plan. At the Monarch quarry, the Castle Butte Member con- sists of two stratigraphic units. The Upper unit (Mlu) is a thick-bedded, fine-grained crystalline dolomitic limestone from 0 to 300 feet (0-90 m) thick. The unit generally has an Si02 content of less than 4 percent. A bedded chert horizon and a karst horizon at the base of the unit locally raise the Si02 content as high as 20 percent. The underlying Quarry Stone unit (Mlq) is a light-gray, massive, bedded, calcilutite/micrite limestone from 90 to 130 feet (27-40 m) thick. The Quarry Stone unit is remarkably uniform chemically throughout it's entire thickness. Average analysis is CaC03 - 95 percent, MgC03 - 3.5 percent, and Si02 - 0.5 percent. The Footwall dolomite unit (Mld) of the Redcliff Member of the Leadville Limestone is a dark gray to black, blocky, medium-to-thick-bedded, calcilutite/micrite dolomite from 150 to 180 feet thick (46-55 m). The upper 100 feet (30 m) of the unit is a low-silica facies with an average Si02 content of less than 0.5 percent. MgC03 content is con- sistent at 39.8 percent throughout the upper 50 feet (15 m) of the unit but varies from 15 percent to 39.8 percent in the lower portion (50 to 100 feet [15-30 m]) of the low-silica facies. The lowest portion of the unit, 100 feet (30 m) to base of unit is high in silica and is not considered chemical grade. Current in-place, surface-minable reserves at the quarry are estimated to be 14 million short tons (st) (13 million metric tons [mt]) of limestone and 50 million st (45 million mt) of dolomite. A 1.4 million st (1.3 million mt) stockpile of finely crushed limestone is also present on the property. Colorado Lime is presently processing approximately 2,000 st (1,800 mt) per month from the crushed limestone stockpile. This material is pulverized and sold to underground coal mines for use as rock dust, some of this product is also used for environmental purposes. Limestone mining is scheduled to resume in spring of 2000.

Jan 1, 2001

By E. Spencer

Overexposure to hazardous noise has been found in most mining sectors, with up to 100% of the surveyed workforce experiencing a noise dose over the Mine Safety and Health Administration (MSHA) permissible exposure level (PEL). As a result, miners show elevated rates of hearing impairment of 70-90% by retirement age. To help manage noise exposures, the National Institute for Occupational Safety and Health (NIOSH) developed the Determination of Sound Exposures (DOSES) software and implementation guide for use by mine management and safety personnel. The software relies on a time-motion study that profiles the worker?s daily activities. Observations about the worker?s location and tasks or other activities are recorded along with the start and end time, to determine the duration of the tasks, so they can later be matched up with the noise data. The software gives the user the option of assessing dose relative to the MSHA PEL, the Action Level or the NIOSH Recommended Exposure Limit. The software generates a variety of interactive onscreen displays showing where, when, and how the worker?s noise dose accumulated. It also can generate customizable printed reports. These outputs can be used to highlight the tasks, locations, and times that are associated with the greatest amount of the worker?s noise exposure. DOSES simplifies the record keeping and analysis associated with time-motion studies and worker noise exposures, so mine management can make engineering noise control or administrative control decisions to limit the noise over-exposure of their workers.

Jan 1, 2010

By Jay Parrish

Appalachian kimberlites appear to be spatially distributed along two structure parallel trends running from Tennessee to New York. It is hypothesized that the kimberlites were emplaced at the intersection of structure parallel basement faults and cross- structural lineaments. The latter are expressed in potential field and remotely sensed data. The western trend follows the Rome Trough from eastern Kentucky to south central New York. The eastern trend parallels the edge of the Ridge and Valley in Virginia and Maryland.

Jan 1, 1984