Turin, depicting the workings of an Egyptian gold-mine. It was drawn in the reign of the king Mineptah, 1,400 years before the Christian era. Land-surveying was first practised in Egypt. There the annual overflows of the Nile, and the consequent deposit of mud, destroyed the land-marks of the different proprietors, so that it became necessary to determine them by measurement every year. The oldest evidence of the solution of mathematical problems is afforded by a papyrus in the British Museum, which is believed to have been copied, 1,700 years B.C., from a much older work. It gives rules for the calculation of areas of triangles, trapezoids, and circles.

That the important mines of the ancient Greeks necessitated the solution of mine-surveying problems is shown by the fact that such problems are fully discussed by Hero of Alexandria (B.C. 285-222), several of whose works are extant. The greatest advance in survey practice made by Hero was his invention of the diopter, a sighting instrument for surveying purposes. The oldest instrument for measuring angles, like the cross-head which is still in use, only permitted right angles to be set out. This primitive instrument consisted of two straight-edges fastened together at right angles, a pointed vertical staff being fixed to the point of intersection. The two straight-edges were provided at each extremity with sight vanes, from which plumb-lines were suspended so as to enable the instrument to be levelled. With Hero's improved instrument, any angle could be measured. Indeed, it must be regarded as the origin of the highly perfect theodolite of the present day. It consisted essentially of a beam resting between two uprights on a pillar-like stand. The beam was movable in both directions by means of spiral screws acting on horizontal and vertical cog-wheels. It was hollowed out, and contained a metal tube, at right angles to which were glass cylinders at each end of the beam. The cylinders had special covers made of metal plate, which could be raised or lowered by means of screws. They were furnished with vertical and horizontal slits for sighting. The instrument was thus a combined theodolite and level. Two staves with sliding circular vanes were used in conjunction with it.

From the beginning of the Christian era until the Middle Ages, mining records are wanting. An ancient charter relative to the mines of the Mendip Hills is in existence. Of this Mr. Robert Hunt gives a fac-simile in his British Mining. It dates from the reign of Edward IV., about 1480. It is a rude attempt at plan-drawing, representing the "Myne deeps," as they were then called.

The first writer who treated mining systematically, Georgius

Agricola, in his work De re Metallica, published in 1556, devotes an entire section (Book V.) to mine-surveying. He states, as has been frequently repeated since, that the ancient minesurveyors strenuously endeavoured to keep their art a secret. In the Middle Ages they were in consequence superstitiously regarded as sorcerers. The divining-rod was closely associated with the practice of their profession, and in many cases that hazel-twig was trusted more implicitly than the most scientific surveying operation.

In 1686 appeared the first treatise on mine-surveying, the Geometria Subterranea of Nicolaus Voigtel. This was followed by the treatises of J. F. Weidler, 1726 (in Latin); and of H. Beyer, 1749, and von Oppel, 1749 (in German). These works, by advocating the plotting of mine-surveys by means of rectangular co-ordinates, lifted mine-surveying to a higher plane.

In Great Britain, instructions for making mine-surveys were published by Thomas Houghton in 1681 for the Derbyshire miners, by William Pryce in 1778 for the Cornish miners, and by Thomas Fenwick in 1804 for the Newcastle colliers.

Importance of Mine-Surveying. When the enormous value of mineral resources is considered, the high importance, from_a commercial point of view, of the art of mining is apparent. In the United Kingdom alone, the annual value of minerals raised has approached £80,000,000, the result of the labours of some 500,000 persons directly employed in their extraction. It thus becomes a matter of the utmost importance that the extent and character of the mineral deposits should be made known. This can only be effected by careful and accurate surveys.

Mine-surveying, unfortunately, has not kept pace with the advances made in other branches of surveying; for it is to be regretted that, in many cases, mine-surveys are still made with instruments which have long been set aside as too inaccurate for surveys aboveground, although the latter rarely present such serious difficulties as are encountered underground. This is, in part, due to the conservatism of miners, a conservatism which has frequently led them to regard with contempt every kind of knowledge except that learned underground. It is a fact, as Mr. R. Hunt points out, that the untrained mind, as a rule, treasures every truth as a mystery to be carefully guarded for individual use only. Experience has often stored an individual mind with valuable facts, which are rarely recorded. The miner trusts to his memory, and, when he dies, the results of his experience die with him. The son has to begin where the father began, and this is repeated from generation to generation, so that there has been no advance. These remarks apply more parti

cularly to the miners of the county of Cornwall, where the mining proverb, "Where it is, there it is," still holds its own.

Happily, a better system is beginning to prevail. Coal-mining is now carried on with a high degree of skill. Colliery managers, who formerly were generally ignorant of the theoretical principles upon which practice is based, are now submitted to a severe educational test before a certificate of competency is granted. It is, however, to be regretted that a similar examination has not been instituted for the agents of metalliferous mines. The mining schools which have been founded in various districts offer suitable opportunities for the necessary theoretical training, as also do the local classes held under the Science and Art Department, and under the City and Guilds of London Technical Institution.

Another cause which has retarded the progress of mine-surveying is the uncertain and speculative nature of mining. Casual failures, caused by the want of easily accessible information, frequently lead to the abandonment of highly promising mines. Mining, though speculative, is not entirely the work of chance; and he who, avoiding vague and unsatisfactory speculations, constantly stores up facts, and can grasp the extent and object of mining works, is frequently enabled to avoid expenses and difficulties, in which those who are without such data would soon be involved.

In this connection, Sir Warington Smyth, in a lecture on mining, says: "At the present time, few large collieries or metalliferous mines are conducted without the aid of a satisfactory plan, but there are very numerous mines in which this department is much neglected. Moreover, there is generally a want of uniformity in system, an absence of details which should give all the information that can be laid down on paper, a deficiency of surface-objects by which the workings can at a future day be referred to their proper position, and (what may sometimes lead to the most fatal errors) a neglect of observation or notice of the variation of the magnetic-needle, according to which mining plans are almost invariably constructed. It is too often the case when mines are worked by companies, that the shareholders are so regardless of what does not, as they conceive, lead to immediate gain, that they grudge the moderate sums needful for the employment of properly qualified surveyors, and either wink at the total neglect of plans, or leave them to be carried out by men already sufficiently tasked or incapable, although they may dial with accuracy, of representing on paper what they have measured."

As an example of an error involving great loss, serious danger, and future grave embarrassments, it may be mentioned that,

according to Mr. P. W. Stuart-Menteath, at an important mine in Spain an incorrect survey caused an error of 65 metres to be made in driving a main tunnel less than 200 metres in length. In collieries, too, examples are not wanting. Thus, in 1875, at a small colliery in Nottingham there was an accident owing to some old workings. Trusting the old plans, which showed a barrier 100 yards away, the men worked into the old headings with disastrous results. Another case is recorded by Mr. J. Dickinson in 1878, when an inundation occurred by which two lives were lost, from a former working being cut into without any bore holes in advance. In this instance, there was a correct plan of the former work, but by a mistake of the surveyor, a wrong direction was set out. Mineral Deposits. For practical purposes mineral deposits may be divided into tabular deposits, including mineral veins, beds, and seams, and irregular deposits, including masses, stockworks, and pockets. Tabular deposits are those in which two dimensions predominate. The third smaller dimension, the perpendicular distance between the two bounding planes, is termed the thickness. The rock on both sides of these two planes is termed the country rock, the portion on which the deposit lies is the foot-wall, and that covering the deposit is the hanging-wall. With beds and seams, these are known as the floor and roof respectively. The strike or course of a deposit is the angle formed with the meridian by the direction of a horizontal line drawn in the middle plane. Its dip is the inclination downwards measured in degrees from the horizontal. As the dip of veins is usually great, it is somtimes measured from the vertical, and is then termed underlie or hade. The portion of a mineral deposit occurring at the surface is known as the outcrop, basset, or (U.S.) apex.

Mineral veins or lodes are defined by Dr. C. Le Neve Foster as tabular deposits of mineral, which have been formed subsequently to the rocks by which they are surrounded. Usually, they occupy fissures in the earth, frequently cutting across the planes of stratification of the rocks. They may occur in eruptive or in sedimentary rocks. Their contents vary, some parts containing worthless vein-matter or gangue, others being filled with ore. The productive portions are termed shoots or courses of ore, bunches, or ore-bodies. Cross courses are veins coursing nearly at right angles to the chief lodes of any particular mining district. The characteristic feature of beds and seams is, that they are members of a series of stratified rocks. They may be interstratified deposits, or superficial ones, such as peat, bog iron ore, gold placers, and tin stream-works. In the former case, they are younger than the floor, and older than the roof. As stratified deposits, they were originally deposited in a more or less hori

zontal form, and follow all the contortions of their country rock. The minerals occurring in bedded deposits are coal, anthracite, lignite, iron ore, cupriferous-shale, lead-bearing sandstone, gravels containing diamonds, or gold, or tin, sulphur, salt, clays, limestone, gypsum, oil-shale, alum-shale, and slate. Miners often erroneously speak of "veins" of coal or ironstone; these, geologically, are true "beds or seams.

"Masses" are deposits of mineral of irregular shape, which cannot be recognised as beds or as veins. Such, for instance, are the red hæmatite deposits of Ulverston, the brown hæmatite of the Forest of Dean, the iron ore deposits of Missouri, the iron mountains of Gellivara and Taberg in Sweden, and the pipes of diamond-bearing rock in South Africa. They may be filled-in cavities or metamorphic deposits, such as the zinc ore deposit of Altenberg, which is 260 yards long and 65 yards broad and deep. When the whole rock is permeated with mineral matter, accumulated in minute veins, the deposit is termed a stockwork. Examples of such deposits are afforded by the decomposed granite worked for China clay at Saint Austell, and other places in Cornwall.

No classification of mineral deposits can be quite satisfactory in all cases. A bed, for instance, even of coal may be so folded and contorted as to lose its original tabular form, and to assume the shape of an irregular mass.

Mining Terms. Many local as well as technical terms are used in mining. The following are definitions of some of the objects most frequently named on mine-plans :-A shaft is a pit sunk down from the surface. In the mining of stratified deposits, the shafts sunk are usually perpendicular. In vein-mining, they may be sunk perpendicularly to cut the vein, or they may follow its underlie. Levels are horizontal excavations along the course of a vein, or horizontal passages, by which access is gained to the workings of the mine. A level driven from the surface, to draw off the water, is termed an adit level, or (U.S.) a tunnel. A drift or gallery driven across the usual direction of the veins generally for the purpose of searching for a new vein, or of connecting two known veins, is termed a cross-cut. The extreme end of any level or cross-cut is called the forebreast or end. A stope is the working from which the ore is extracted. Above a level, the working is an "overhand" or back stope; an "underhand" stope is the working downwards from the floor of the level. A winze is a shaft which connects two or more levels, but does not come to the surface. A rise is an upright winze commenced from a level; a sump is a winze worked downwards. Surface workings include open cuts, pits, and excavations of limited extent. A tract of