geology, with the most common fossils of each. The rocks most common in coal measures are sandstones, limestones, shale, conglomerates, fireclays, and, in some localities, the coal deposits are frequently associated with beds of iron ore. The preceding table gives the names of the various geological eras, periods, epochs, and stages as they occur in the United States, together with the kinds of rocks characterizing each. Faults. Frequently a seam becomes faulted or pinched out underground, and it is necessary to continue the search by means of underground prospecting. If a fault or dislocation is encountered, the manner of carrying on the search will depend on the character of the fault. Where sand faults or washouts are encountered, the drift or entry should be driven forwards at the angle of the seam until the continuation of the formation is encountered, when a little examination of the rocks will indicate whether they are the underlying or overlying measures. In the case of dislocations or throws, the continuation of the seam may be looked for by Schmidt's law of faults, which is as follows: Always follow the direction of the greatest angle. It has been discovered that, in the majority of cases, the hanging-wall portion of the fault has moved down, and on this account such faults are commonly called normal faults. For instance, if the bed ab, of the accompanying figure, were being worked from a toward the fault, work would be continued down on the farther side of the fault toward d, until the continuation of the bed toward b was encountered. In like manner, had the work been proceeding from b, the exploration would have been carried up in the direction of the greatest angle, and the continuation toward a thus discovered. A reverse fault is one in which the movement has been in the opposite direction to a normal fault. Especially in the case of those mines where the material occurs as perpendicular or steeply pitching veins, faults are liable to displace the seam both horizontally and vertically, in which case it may be difficult to determine the direction of the continuation of the bed; but frequently pieces of coal or slate are dragged into the fault, and these serve as a guide to the miner, and indicate the proper direction for exploration. Where a bed or seam is faulted, its continuation can frequently be found by breaking through into the measures beyond, when an examination of the formation will indicate whether the rocks are those that usually occur above or below the desired seam. EXPLORATION BY DRILLING OR BORE HOLES Earth Augers. When testing for coal seams that occur comparatively near the surface, hand augers may be employed to great advantage. A good form of hand auger consists of a piece of flat steel or iron, with a steel tip, twisted into a spiral about 1 ft. long, and having four turns. The point is split and the tips sharpened and turned in opposite directions and dressed to a standard width, usually 2 in. The auger is attached to a short piece of 1-in. pipe, and is operated by joints of 1-in. pipe, which are coupled together with common pipe couplings. The auger is turned by means of a double-ended handle having an eye in the center through which the rod passes. The handle is secured by means of a setscrew. In addition to the auger it is well to have a straight-edged chopping bit for use in comparatively hard seams. This may be made from a piece of 1-in. octagon steel, with a 2-in. cutting edge. The upper end of the steel is welded on to a piece of pipe similar to that carrying the auger. When the chopping bit is employed, it is necessary to have a heavy sinking bar, which may be made from a piece of solid 1-in. iron bar, fitted with ordinary 1-in. pipe threads on the ends. Prospecting can be carried on to a depth of from 50 to 60 ft. with this outfit. The number of men necessary to operate the rods varies from two to four, depending on the depth of the hole being drilled. When more than 30 ft. of rods are in use, it is usually necessary to have a scaffold on which some of the men can stand to assist in withdrawing the rods. When withdrawing the rods, to remove the dirt, they are not uncoupled unless over 40 ft. of rods are in use at one time, and sometimes as many as 50 or 60 ft. are drawn without uncoupling. Percussion Drills.-Percussion, or churn, drills are frequently employed in drilling for oil, water, or gas, and were formerly much used in searching for coal and ores, but, owing to the fact that they all reduce the material passed through to small pieces or mud, and so do not produce a fair sample, and to the fact that they can only drill perpendicular holes, they are at present little used in prospecting for either ore or coal. COST OF WELL DRILL Size of Well Inches 68025 10 12 ING Cost per $1.50 The cost and rate of drilling by means of a percussion or churn drill varies greatly, being affected much more by the character of the strata penetrated than is the case with the diamond drill. In the case of highly inclined beds of varying hardness, the holes frequently run out of line and become so crooked that the tools wedge, and drilling has to be suspended. For drilling through moderately hard formations, usually encountered in searching for gas or water, such as sandstones, limestones, slates, etc., the accompanying costs, from the American Well Works, Aurora, Ill., may be taken per foot for wells from 500 to 3,000 ft. deep for the central or eastern portion of the United States. This cost includes the placing of the casing, but not the casing itself. When drilling wells for oil or gas to a depth of approximately 1,000 ft., using the ordinary American rig with a cable, the cost is sometimes reduced to as little as 65 c. per ft. for 6-in. or 8-in. wells; this is when operating in rather soft and known formations. From 15 to 40 ft. per da. of 24 hr. is usually considered a good rate of drilling, though in soft materials as much as 100 ft. may be drilled in a single day, and at other times, when very hard rock is encountered, it is impossible to make more than from 1 to 2 ft. per da. Percussion Core Drill.-In order to overcome the chief objection to the use of percussion drills in coal prospecting work, an attachment is now provided which can be used in connection with the ordinary oil-well drilling outfit and by means of which a core of a coal seam may be recovered. A 6-in. hole is sunk with the ordinary tools until the vicinity of the bed to be cored has been reached. The tools are then withdrawn, the bit and stem are removed, leaving the jars and rope socket attached to the cable, and the core drill is attached to the jars. This drill is a steel pipe about 14 ft. long provided with chiselshaped cutting teeth, and within which is placed the core-barrel. The hole is carefully cleaned with the sand pump and its exact depth measured and recorded. This core-drilling attachment is lowered carefully into the hole until it rests on the bottom and drilling is resumed in the ordinary way at a moderate speed but with a stroke of from 15 to 18 in. After drilling 20 or 30 in. the tools are withdrawn; a slight jar is sometimes necessary to break the core loose. At the top of the hole, the tools are swung to one side, the core barrel with the contained core removed from the drill and another core barrel attached if a longer core is needed. Drilling operations are resumed while the core is being removed from the core barrel just brought up. The core barrels are of two lengths, the shorter ones being designed for use in hard formations like sand rock, limestone, etc. Core Drills. What are known as core drills are the only forms that have proved successful in drilling in any direction through hard, soft, or variable material. Even with core drills, many difficulties present themselves and demand careful study in adapting the form of apparatus to the work in hand, and in rightly interpreting the results obtained from any set of observations. Core drills are of two main types, the diamond drill and the calyx drill. The two are essentially alike in consisting of a cutting bit attached to the end of a series of connected rods to which a rotary motion is applied by a steam, electric, compressed-air, or gasoline motor. In the diamond drill, the cutting bit consists of a hard steel cylinder in the bottom rim (both inner and outer edges) of which are set fragments of black diamond (bort, or carbonado) the edges of which slightly project beyond the metal surface of the bit. Being the hardest substance known, upon being rotated, the diamonds naturally cut out a cylindrical core of any rock penetrated. The bit of the calyx drill is of two forms. For drilling in comparatively soft rock, it consists of a steel cylinder with chisel-shaped teeth that cut and scrape away the rock. For drilling in harder rock, the bit is without teeth, being merely a ring of metal with a slot in the side through which chilled steel shot fed into the bore hole above find their way so that they may be rolled over the surface of the rock to be cut as the bit is rotated in the hole. While the following is intended primarily to guide in the selection, use, etc., of a diamond drilling machine, it is also applicable to the calyx drill. Selecting the Machine.-It is not economy to employ a machine of large capacity in shallow explorations, as the large machines are provided with powerful motors, and hence do not work economically under light loads. When a large machine is operating small rods on light work, the driller cannot tell the condition of the bit, or properly regulate the feed. The machine should possess a motor of sufficient capacity to carry the work to the required depth, but where much drilling is to be done, it is usually best to have two or more machines, and to employ the small ones for shallow holes, and the large ones for deep holes. All feed mechanisms employed in diamond drilling may be divided into two classes: Those that are an inverse function of the hardness of the material; this class includes friction, spring, and hydraulic feeds. Those in which the feed is independent of the material being cut, as in the case of the positive gear-feed. The first class is advantageous when drilling through variable measures in search of fairly firm material, which does not occur in very thin beds or seams. On account of the fact that this class of feed insures the maximum amount of advance of which the bit is capable in the material being cut, the danger is that the core from any thin soft seam may be ground up and washed away, without any indication of its presence having been given. The second class, or positive gear-feed, if properly operated, requires somewhat greater skill, but if used in connection with a thrust register, it gives reliable information as to the material being cut, and is especially useful when prospecting for soft deposits of very valuable material. Size of Tools.-The size of tools and rods, and consequently the size of the core extracted, depends on the depth of the hole and the character of the material being prospected. When operating in firm measures, such as anthracite, hard rock, etc., it is best to employ a rather small bit, even when drilling up to 700 ft., or more, in depth. For such work, a core of from 1 to 1 in. is usually extracted. The rate of drilling with a small outfit is very much greater than with a large one, owing to the fact that there is a small cutting surface exposed, and the rate of rotation of the rods can be much greater. When prospecting for soft materials, such as bituminous coal, valuable soft ores, or for disseminated ores, such as lead, copper, gold, silver, etc., it is best to employ a larger outfit and extract a core 2 or 3 in. in diameter, and sometimes larger, even though a comparatively small machine is used to operate the rods. Diamond-Drilling.-Drift of diamond-drill holes, or the divergence from the straight line, often becomes a serious matter. This trouble may be minimized by keeping the tools about the bit as nearly up to gauge as possible. Core barrels, with spiral water grooves about them, answer this purpose very well if they are renewed before excessive wear has taken place. Surveying of diamond-drill holes may be carried on by either one of two methods, depending on the magnetic conditions of the district. Where there is no magnetic disturbance, the system developed by Mr. E. F. MacGeorge, of Australia, may be employed. This consists in introducing into the hole, at various points, small tubes containing melted gelatine, in which are suspended magnetic needles and small plummets. After the gelatine has hardened the tubes are removed, and the angles between the center line of the tube, the plummet, and the needle noted, thus furnishing the data from which the course of the hole can be plotted. This method gives both the vertical and the horizontal drift. Where there is magnetic disturbance the needle cannot be used, but a system brought out by Mr. G. Nolten, of Germany, has been quite extensively employed. In this case, tubes partly filled with hydrofluoric acid are introduced into the hole, at various points, and the acid allowed to etch a ring on the inside of the tube. After the acid has spent itself the tubes are withdrawn, and by bringing the liquid into such a position that it corresponds with the ring etched on the inside of the tube, the angle of the hole at the point examined can be determined. This method gives a record of the vertical drift of the hole only. The value of the record furnished by the diamond drill depends largely on the character of the material sought. The core extracted is always of very small volume when compared with the large mass of the formation prospected, and hence will give a fair average sample only in the case of very uniform deposits. The value of the diamond drill for prospecting may be stated as follows: More dependence can be placed on the record furnished by the diamond drill when prospecting for materials that occur in large bodies of uniform composition than when prospecting for materials that occur in small bunches or irregular seams. To the first class belong coal, iron ore, low-grade finely disseminated gold and silver ores, many deposits of copper, lead, zinc, etc., as well as salt, gypsum, building stone, etc. To the latter class belong small but rich bunches of gold, silver mineral, or rich streaks of gold telluride. The arrangement of holes has considerable effect upon the results furnished. If the material sought lies in beds or seams (as coal), the dip of which is fairly well known, it is best to drill a series of holes at right angles to the formation. If the material sought occurs in irregular bunches, pockets, or lenses, it will be necessary to drill holes at two or more angles, so as to divide the ground into a series of rectangles, thus rendering it practically impossible for any vein or seam of commercial importance to exist without being discovered. Where the surface of the ground is covered with drift and wash material, it may be best to sink a shaft or drill pit to bed rock, and locate the machine on bed rock. After this, several series of fan holes may be drilled at various angles from the bottom of the pit. Owing to the upward drift of diamond-drill holes, the results furnished from a set of fan holes drilled from a single position would make a flat bed appear as an inverted bowl, or the top of a hill. On this account, it is best to drill sets of fan holes from two or more locations, so that they will correct one another. If fan holes from different positions intersect the same bed, a careful examination of them will usually furnish a check on the vertical drift of the holes. The speed and cost of drilling depend on the hardness and character of the rock, the size of the hole, the depth of the hole, and the height of the derrick. Sedimentary rocks, such as sandstones, slates, and limestones are generally more rapidly drilled than the much harder and unstratified igneous rocks, and firm rocks than those that cave and require that the hole be cased. Cores of moderate size, say, up to 1 to 2 in. in diameter can be taken out more rapidly and hence at less labor cost (the chief item in drilling) than larger ones, and answer just as well for determining the nature and value of the rocks passed through. The deeper the hole, the more costly and the less the progress per shift, because of the time lost in pulling the drill rods and removing the With deep holes the labor cost is materially reduced if the derrick is sufficiently high to permit unscrewing the drill rods at every fourth joint while raising them for the purpose of extracting the core. cores. The actual rate of drilling, including pulling the rods, removing the cores, etc., is dependent on the depth of the hole. In shallow holes, a rate of 2 ft. per hr. is fair; in holes of moderate depth, say, up to 700 ft., a rate of 1 ft. per hr. should be secured. Prospecting with core drills is usually done under contract at an agreed sum per foot, which is determined by the number of holes, their average depth, size of core extracted, distance apart of the holes, etc. Contract prices for diamond drilling in the bituminous coal regions range from $2 to $2.75 per foot for extracting cores up to say, 1 in., where the holes range from 150 to 500 ft. in depth (averaging, say, 250 ft.), where from 1,200 to 2,000 ft. of drilling is required, and where the coal and water are furnished the contractor. Where the drill is owned by an operating coal company, the cost of ordinary drilling should be less than $1 per ft., including labor, diamonds, and ordinary repairs. Calyx Drilling.-The calyx drill will do essentially the same work as the diamond drill, except that it will not cut at angles of over 45° because the shot will roll to and remain at the lower side of the hole, and even this pitch is too flat for really satisfactory work. The gain in the use of the calyx over the diamond drill consists in the saving in cost of the abrasive material used. Black diamonds are now quoted as high as $90 a carat for the larger and better stones, so that a single bit will often cost from $750 to $2,000, according to size. There should be at least two bits in stock, so that one may always be in condition for use. If drilling is carried on a long distance from the base of supplies, three, four, or even more bits must be available, or else a diamond-setter must be employed. Setting diamonds is highly skilled labor and is paid accordingly. When the material is so soft that the shot wedge or press into it the bit with teeth is to be preferred to the shot bit, the latter coming in use when the rock is firm sandstone, limestone, and the like. The amount of shot used varies with the hardness of the material being drilled. Shale, slate, limestone, and ordinary sandstone may require from to lb. of shot per foot of hole. Very hard sandstone, granite, quartz conglomerate, porphyry, taconite, and jasper require from 1 to 4 lb. per ft. Another material sometimes used is crushed steel, variously sold under such names as "diamondite," "abrasite," etc. While ordinarily inferior to chilled shot, and not giving such satisfactory results, for comparatively soft formations it is sometimes better than shot. The calyx drill, like the diamond drill, is manufactured to be operated by hand or horsepower for use in boring shallow holes, and is also to be had mounted on a wagon-like frame with attached derrick for ease in transportation. Prospecting for Petroleum, Natural Gas, and Bitumen.-Among the surface indications of petroleum and bitumen may be mentioned white leached shales or sandstones, shales burned to redness, fumaroles, mineral springs, and deposits from mineral springs. Also natural gas, springs of petroleum oil and naphtha, porous rocks saturated with bitumen, cracks in shale, and other rock partly filled with bitumen. Petroleum is never found in any quantity in metamorphic rocks, but always in sedimentary deposits. Bitumen can be told from coal, vegetable matter, iron, manganese, and other minerals, which it sometimes closely resembles, by its odor and taste, also by the fact that it melts in the flame of a match or candle, giving a bituminous odor. (Iron and manganese do not fuse, and coal and vegetable matter burn without fusion.) Bitumen is also soluble in bisulphide of carbon, chloroform, and turpentine, usually giving a dark, black, or brown solution. Frequently, springs or ponds have an iridescent coating of oil upon the surface. Sometimes iron compounds give practically the same appearance, but the iron coating can always be distinguished from the oil by agitating the surface of the water, when the iron coating will break up like a crust of solid material, while the oil will behave as a fluid, and tend to remain over the entire surface even when it is agitated. Frequently, bubbles of gas are seen ascending from the bottoms of pools or creeks. These may be composed of carbureted hydrogen or natural gas, which is a good indication of the presence of petroleum or bitumen; they may be composed of sulphureted hydrogen or carbonic-acid gas. Carbureted hydrogen can be distinguished by the fact that it burns with a yellow luminous fame whereas sulphureted hydrogen burns with a bluish flame, and carbon dioxide will not support combustion, but, on the contrary, is a product of combustion. When carbureted hydrogen gas is discovered ascending from water, the bottom of which is not covered with decaying vegetation, it is almost a certain sign that there is petroleum or bitumen somewhere in the underlying or adjacent formations. If natural gas or bitumen is found upon the surface of shale, it is probable that the material ascended vertically through cracks in these rocks from porous strata below; while if it is found in connection with sandstones, it is probable that the material was derived from the porous sandstone itself. This is especially liable to be true if the sandstone has a steep pitch. As a rule, deposits of bitumen or petroleum occur in porous formations overlaid by impervious strata, such as shales, slates, etc. Anticlines are more liable to contain such deposits, though they are not absolutely necessary to retain them, as at times portions of the underlying porous strata have been rendered impervious by deposits of calcium salts, silica, etc., and hence the petroleum or bitumen will be confined to the porous portions. Natural gas also occurs under similar conditions, but usually in anticlines only. Construction of Geological Maps and Cross-Sections.-After the surface examination of a property is complete, the data should be entered on the best map procurable, or a map constructed. The scale depends on the size of the property, the complexity of the geological formation, the value of the property, and the material to be mined from it. The amount of work that it will pay to put on the survey will depend largely on the value of the property, more detail being justified in the case of high-grade properties. If a property 1,200 ft. X3,000 ft. (the size of four U. S. metal mining claims) were to be surveyed and mapped with a scale of 1 in. equal to 100 ft., the map would be 12 in, X30 in. A stratum 10 ft. wide on this map would appear as to in. wide, which is about the smallest division that could be shown with its characteristic symbol; for greater detail, a larger scale, or larger scaled sheets of the most important portions of the deposit, will be necessary. If the geologist constructs the topographical contour map, he can take notes on the geology at the same time. When the boundaries of the property are being surveyed, certain points should be established, both vertically and horizontally, as stations in future topographical work. If the map is on government surveyed fand, the government lines may be used for horizontal locations, but it will be necessary to determine the elevation of the different points. If the property |