UNIVERSnTgrCftLIFORNIA COLLEGE of MINING DEPARTMENTAL LIBRARY * BEQUEST OF SAMUELBENEDICTCHRISTY PROFESSOR OF MINING AND METALLURGY 1885-1914 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. BY DUNBAR D. SCOTT AND OTHERS. tl COMPRISING THE ORIGINAL PAPER OF MR. SCOTT ON THE SUBJECT, TOGETHER WITH THE DISCUSSION THEREOF, AND INDE- PENDENT CONTRIBUTIONS ON THE SUBJECT. Reprinted from Vols. XXVIII-XXXI of the Transactions of the American Institute of Mining Engineers. NEW YOKE CITY : PUBLISHED BY THE INSTITUTE AT THE OFFICE OF THE SECRETARY. 1902. t MIMINtf 0PT, PREFACE. THIS volume contains by no means the whole of the discus- sion elicited by the original paper of Mr. Scott. Additional contributions, received too late for introduction here, will be found in the Transactions of the Institute, to which the reader is referred. This circumstance is, however, less to be lamented than if it had been possible, by a little longer delay, to close the whole discussion, leaving nothing to be corrected or added. But the subject is one of those which will never be exhausted; and there would be greater cause for regret if the issue of this volume should be construed by practising mine-surveyors and the designers or makers of surveying-instruments as an intima- tion that further statements of fact, argument or criticism would not be welcomed by the Council of the Institute. I trust that such a misunderstanding will be effectively prevented by the appearance in Vol. XXXI. of the Transactions of the interesting additional papers of Mr. II. D. Hoskold, to say nothing of minor contributions on the subject, none of which have been included in the present volume. It is believed, nevertheless, that the material here presented comprises, in compact and convenient form, information of sufficient scope and value to warrant the issue of the book by the Institute. R. W. RAYMOND, Secretary. 303741 CONTENTS. PAGE PREFACE, iii The Evolution of Mine-Surveying Instruments ; by Dunbar D. Scott, . . 1 DISCUSSION : Secretary's Note, . V ... . . 68 Bennett H. Brough, . . . . ...... . 68 D. D. Scott, . . . . > 71 W. F. Stanley, . . . . ... . . . . 75 D. D. Scott, . ,...'.' ..... . . . 76 C. L. Berger & Sons, . . .' . . '. . . . . 77 F. W. Breithaupt & Sohn, . '.... 78 Prof. Dr. Max Schmidt, 82 D. D. Scott, 86 D. W. Brunton, 88 H. D. Hoskold, . . . 91 D. D. Scott, 119 Jas. B. Cooper, . 121 W. S. Hungerford, ....... ... 123 D.D.Scott, . -. . .... ; ' . . .... 126 J. E. Johnson, . . . j , . 129 Julius Kellerschon, . ..; , ., .... . . 133 P. & K. Wittstock, .- . . . . . ,* 13f > Edwin J. Hulbert, . . . . . . .... 146 Alfred C. Young, .. . v . . . . . ' . . . 152 Frank Owen, . . .. . . * . ' . .. . . . 164 K. W. Kaymond, . . . . ... . . 166 History of Solar Surveying-Instruments ; by J. B. Davis, . . . . 172 Eemarks on Mine-Surveying Instruments, with Special Keference to Mr. Dunbar D. Scott's Paper on their Evolution, and its Discussion ; by H. D. Hoskold, 206 Notes on Mine-Surveying Instruments, with Special Keference to Mr. Dunbar D. Scott's Paper on their Evolution, and its Discussion ; by Benjamin Smith Lyman, ........ 237 Notes on Tripod-Heads, with Eeference to Mr. Scott's Paper, etc. ; by John H. Harden, 290 The Evolution of Mine-Surveying Instruments, Concluding Discussion ; by Dunbar D. Scott, .......... 293 Index, 309 Errata, 323 (v) THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. BY DUNBAR D. SCOTT, PHOENIX, MICH. THE development in the perfection of mine-surveying instru- ments has heen by no means rapid, as it has depended some- what on the details of construction borrowed from astronomical and geodetic theodolites, largely on the restrictions laid down by mining companies and the prejudices of mine managers themselves, but more than all on the methods used in conduct- ing surveys and the importance attached thereto. Mine-surveying, in some form or other, has been practiced from the very earliest times ; but it has never kept pace with the other branches of surveying, or even with the art of min- ing itself, and cannot be recognized as an exact science until shortly before the beginning of this century. The works of Hero of Alexandria, who lived in the second century B.C., are still extant, and contain descriptions of a rec- tangular sighting-instrument, which he invented and called a diopter. His improvement upon this simple construction, which possibly he devised for use in the Greek mines for rough level- ing-purposes and for laying out any angle, must be considered, says Hiibner,* as the origin of the highly perfected theodolite of to-day. Whether this instrument came into general use during the first centuries of the Christian era, is not recorded ; in fact, no writer undertakes to tell how mine-surveying was conducted until 1556, in which year Agricola expounds the principles of mining and metallurgy in his De Ee Metallica, devoting the entire fifth chapter to the practice of mine-surveying (see Fig. 1). In mediaeval times those who possessed any knowledge of engineering skill made strenuous effort to keep their art a secret, partly on account of the miners' proverbial conservatism and partly for their own personal aggrandizement, and were, in * Mittheilungen aus dem Markscheidewesen, von Werneke, Freiberg, 1887. 2 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. consequence, superstitiously regarded as sorcerers of the kind who were expert in the use of the divining-rod. Indeed the superstition of this period was so potent in its in- FIG. l. Facsimile from De Re Metallica, Georgius Agricola, Basel, 1556, constituting the frontispiece of Bennett H. Brough's "Treatise on Mine-Surveying," London. 1888. fluences that the hazel-twig, in the hands of a sensitive medium r was accepted at that time with greater confidence than the most scientific mathematical deduction then possible. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 3 Dr. Raymond published, in 1883, a very complete and inter- esting paper on "The Divining-Rod,* in which reference is made to all the best works on the subject, both ancient and modern. In the study of the history of the subject, he says : " It will appear that divining-rods were first used in antiquity mainly or wholly for moral purposes ; that in the Middle Ages their employment was for a long period confined to the discovery of material objects ; that towards the end of the seventeenth century the moral use was again asserted, and that in the eighteenth century the divining-rod was relegated to the material sphere and assumed the comparative modest functions in the discharge of which it still lingers among us."f And after showing that the rod itself serves, at most, to ex- hibit the results of nervous sensibility and unconscious muscular contraction on the part of the operator, he adds :J "To this, then, the rod of Moses, of Jacob, of Mercury, of Circe, of Valen- tine, of Beausoleil, of Vallemont, of Aymar, of Bleton, of Pennet, of Competti even of Mr. Latimer has come at last. In itself it is nothing. Its claims to virtues derived from Deity, from Satan, from sympathies and affinities, from corpus- cular effluvia, from electricalcurrents, from passive perturbatory qualities of organo- electric force, are hopelessly collapsed and discarded. A whole library of learned rubbish about it, which remains to us, furnishes jargon for charlatans, marvellous tales for fools and amusement for antiquarians ; otherwise it is only fit to con- stitute part of Mr. Caxton's History of Human Error. And the sphere of the divining-rod has shrunk with its authority. In one department after another it has been found useless. Even in the one application left to it with any show of reason, it is nothing unless held in skilful hands ; and whoever has the skill may dispense with the rod." Agricola says the subject is open to much dispute ; states the evidence on both sides briefly, but with admirable clearness ; and, while he declines to enter upon a discussion, " neither per- missible nor agreeable," of the virtue which may be imparted to the rod by spells and incantations, he inclines his reader to skepticism. In the quaint wood-cut accompanying this chapter, his " good and sober " miners, who have studied nature, are already digging ore, while the man with the rod is yet pre- paring to discover it. Fig. 2 is taken from the Cosmographia Univer sails of Sebastian Munster, published at Basel in 1550. "This geographical work," says Dr. H. R. Mill, " deals only vaguely with mining, * Trans., xi., 411. f Ibid., p. 413. % Ibid., p. 445. 2 FIG. 2. 4 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. and I fancy the cut of the virgula divina, to which little reference is made, must have been copied from some earlier work." The Latin treatise on mining engineering by J. F. Weidler (Wittenberg, 1726) deals at length with this supernatural method; and even so clever an engineer as Beyern let superstition get the best of his mathematics. As late as 1749 he claims that thorough instruction in mining engineering involves the application of the divining-rod, though he was intelligent enough to insist that, " if there is a difference in the findings of the twig and com- pass, then more de- pendence must be placed in the compass than in the twig." It is recorded in Chi- nese annals that in 2364 B.C. the Emperor Hou-ang-ti, or Hong-Ti, constructed an instru- ment for indicating the South, which, Dr. Gil- bert says,* was brought from Cathay to Italy in 1295 by the renowned Marco Polo.f F 1 a vio Gioj a, of Amalfi, some ten or fif- Ancient Representation of Divining- Rod. teen years later, was doubtless the first Eu- ropean to mount this magnetic needle in a box, but the use of the stationary or Setz-compass (Fig. 3) in mine-surveys is first described in the work of Agricola. An instrument of this original type, bearing the date 1541, is still preserved at the Neudorfer mines in the Harz. Con- cerning it, Prof. Brathuhn says : "The 5.5 cm. compass-box fits into the center of a wooden disk 16 cm. in di- ameter and 2 cm. thick. About it are three concentric grooves filled with wax of * Colcestrends . . . de Magnete Gulielmi Gilberti, London, 1600. f Bailly, Histoire de I' Astronomic Ancienne, Paris, 1775, p. 122. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. different colors. Upon the bottom plate of the compass-box is drawn only a meridian line, marked at its ends M. K. (Meridies) and S. P. (Septentrio). When in use, the compass and disk were put into the circular cavity of a wooden box, and mounted by means of a hole beneath upon a simple staff. ' ' The disk was turned until the needle became coincident with the meridian line ; then the pointer that revolved about its fiducial edge was brought into the direction of any course, as nearly as could be judged by the eye, and a mark was made in one of the wax circles to indicate its azimuth with the meri- dian. "The course was then measured and recorded with the character- ized mark and the color of the wax circle in which it was made. The survey was then reproduced on the surface, commencing usually at the mouth of the shaft, to determine the prox- imity of the underground workings to the boundary -lines." The Setz-Compass. FIG. 4. Fig. 4 is copied from a drawing of that period, and repre- sents an authorized engineer, commissioned hy the govern- ment of Saxony, engaged in conducting a survey with this instrument. In another place in Agricola's work is represented a nude surveyor making ob- servations with a circle of wood, nearly equal in diameter to his own height, which he holds vertically, and which is provided with a weighted index-pendulum. In these two crude yet ingenious ap- pliances we have, no doubt, the origin of the Hangcompass und Gradbogen that came so universally into use throughout the mining districts of Europe. In 1571 Thos. Diggs, the son of Leon- hard Diggs, published in England his Pantometria, in which are described sev- eral instruments for surveying purposes. His masterpiece is Surveying with the Setz-Compass. 6 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. what he called the theodolitus (Fig. 5), perhaps derived from theodiccea, taken in the sense of perfection, as being a most per- FIG. 5. Diggs's Theodolite. feet instrument.* In the 27th chapter, called Longimetria, he says : "It is but a circle divided into 360 grades or degrees, or a semicircle parted into 180 portions, and every of those divisions in 3, or rather 6, smaller parts. . . . The index of that instrument, with the sights, etc., are not unlike to that which the square hath : In his backe prepare a vice or scrue to be fastened in the top of some staffe, if it be a circle, as heere : let your instrument be so large that from the center to the degrees may be a foote in length, more if ye list, so that you not erre in your practices." For steep upward sighting, he used an artificial horizon. In the same year Diggs published his Sfratiaticus, in which he says that while he had access to certain of Roger Bacon's * This derivation is given by Stanley in his work on Surveying Instruments. Bauernfeind says (vol. i., p. 288): " It cannot be said with certainty how the word ' theodolite,' as applied to angle-measuring instruments, originated. It was used in England as early as the sixteenth century, and probably had its origin there. Prevailing opinion, formerly, assigned its derivation to two or three Greek words, one of which was Ai'So? (stone), and basing it upon this derivation the word should be written theodotith. But more recent archaeological research proves that any attempt to associate the word as we now have it with the Greek is a mistake, as it is more probably a corruption of ' the alidade ' by the English from al'idade, the Arabic term applied to the radius of the astrolabium." THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. unpublished MSS. lie discovered a letter from his father, de- scribing a method of " viewing distant objects by placing perspective-glasses at due intervals." This was certainly an application of the principles of the telescope, which he, no doubt, like others, had discovered by personal research and experiment. The period of the casual invention of the telescope is in- volved in some obscurity. Though there is ample evidence that the ancients of Ovid's time knew something of it, its in- troduction as a philosophic instrument probably belongs to Friar Bacon, who conducted his experiments in Paris, and died at Oxford in 1294. Its construction and uses were handed down through the generation^ as a secret, like all other " works of iniquity " that aimed at an advance in science. Later, in 1590, when Jensen, the spectacle-maker, showed his improved instrument to Prince Maurice, he was required, under severe penalty, to divulge no information concerning it, so that only the prince should be aided by it in his warfares ; but Galileo, having had it described to him in 1608, constructed at Padua a telescope of three diameters' power, and presented it to the Doge of Venice. It was not until about this year that the op- ticians of Holland made the prac- tical application of the telescope possible, and inaugurated a new era in the science of astronomy. The first systematic and ex- clusive treatise on mining engi- neering was the Geometria Sub- terranea of Nicholas Yoigtel (Eis- leben, Saxony, 1686), in which the methods and instruments de- scribed exhibit, after a lapse of 130 years, a natural development yet small improvement over those of Agricola. In fact, mine-sur- veys were conducted on the con- tinent, and probably also in England, by Agricola's primitive means, until Balthazar Eossler, in 1633, invented the method of suspending from a taut hempen cord a gimbal-compass (Fig. 6) and clinometer, by which the magnetic bearing, incli- FIG. 6. 8 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. nation and length of any course were at once determined with comparative ease.* The accuracy of this system, which Yoigtel describes, depended largely upon the perfection of graduation, the precision possible in reading the clinometer, the catenary curve of the cord on long courses (augmented by the weight of the instruments hung upon it), and the surrounding at- tractive influences upon the magnetic needle; but it is certainly the first method for the determination of the angular value of precipitous grades without correction for mechanical imperfec- tions in the apparatus. In 1681 Thomas Houghton published a small treatise upon subterraneous surveying in the Derbyshire mines,f in which he described a use of strings,' plumbs and compass very similar to the method of Rossler, except that the dial, in a long rec- FIG. 7. Surveying by Rossler' s Method. tangular box, was applied by hand to the side of a string, held by two persons, and afterwards measured with a rule. The method of Rossler, or some adaptation of it, prevailed throughout Europe with remarkable tenacity up to the begin- ning of this century ; and even to-day, at some mines, no other instruments are used ; while at others the use of these, in con- junction with the theodolite, is not infrequent. For about eighty years the prestige of the method was undisputed, though it underwent various modifications to suit the conditions of prac- tice. Hempen cords gave way to brass chains; but these (like Gunter's, of 1620, which was substituted for Houghton's rule in English collieries) were found to elongate by tension and fric- tion, so that frequent adjustment became necessary. The cat- enary curve of the cord, chain or wire was always a matter of * Die Entwickdung der Markscheidekunst, M. Schmidt, Freiberg, 1889. f Rara Avis in Term, T. Houghton, London, 1681. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 9 perplexity until about 30 years ago, when Prof. A. von Miller- Hauenfels, of Vienna, deduced rules for the suspension of the clinometer in positions to indicate the exact grade between the two stations. In 1775 Hofrath Kastner designed a quadrant-clinometer, which was suspended from the ends of an index-arm bearing a vernier-scale. The plummet was still used, but only for the purpose of insuring the verticality of the zero-point.* In 1877 Schneider designed a complete circle of aluminum, dispensing with the plummet entirely, and substituting an ali- dade with opposite verniers, the verticality of which was deter- mined by a bubble on its lower arm.f The hanging-compass also underwent various reforms in fruitless attempts to employ it successfully in the presence of iron. Up to 1749 it had not been materially changed from its original construction. The works of both A. Beyer, of Alten- berg, and F. W. von Oppel, of Dresden, published in that year, contained nothing new in instrumental construction ; but each introduced the use of sines and cosines in the calculations. In the second edition of Beyer's work, as revised by Lempe in 1785, appeared, for the first time, an illustration of the now common form of hanging-compass (see Fig. 7), said to have been made by Schubert of Freiberg. The most notable modifications of this instrument are com- paratively recent, and include the adjustable forms of Brauns- dorpf (1834), Lendig (1846), Reichelt (1856), Osterland (1860), Lehman (1873), Plamineck (1878), Fuhrmari (1879), and Penk- ert (1880). In the earliest times mine-plans were rare and rude. The object of most surveys was to retrace on the surface the contour of a subterranean opening. " Underground," says Houghton, " the dial is guided by the string, but on the surface the string is guided by the dial." But as the importance of maps became more obvious, the hanging-compass was so modified that the compass-box might be removed and transferred to a brass pro- tractor-plate, where it was clamped in exact position, and the survey was plotted with the same instrument used in making * Lehrbuch der Praktischen Markscheidekunst, O. Brathuhn, p. 34. f Oesterr. Zeitsch. filr Berg- und Huttenwesen, 1877, p. 367. 10 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 8. it. This method is described in the first edition of Voigtel's work (Eisleben, 1686), and is also spoken of in The Exact Sur- veyor by J. Eyre (London, 1654) as though it had been cus- tomary many years previously. Describing the circumferenter of that day, Eyre says : ' ' For portability this instrument exceedeth any other, and is usually made of wood, containing in length about eight Inches, and in breadth about four Inches, and in thicknesse three quarters of an Inch, the left side whereof is divided into divers equall parts, most fitly of twelve in an Inch, to be used as a scale of a pro- tractor, the Instrument of itself being fitting to protract the plat on paper by help of the Needle, and the degrees of Angles, and length of Lines taken in the Field." The idea is creditable ; but its benefits are questionable, in view of the fact that the magnetic influences are not the same in the office as in the mine. Moreover, for plotting-purposes, the delicacy of a 3-inch needle in a circle graduated to only J is not beyond reproach. Since 1801, the protractor-plate itself has been so provided with adjustable tangent- semicircles (see Fig. 8) that it could be used for both purposes ; but, though widely used by mining-captains in Germany, it does not permit very accurate work. The constancy of the mag- netic needle has been questioned only in times which must be considered as recent, compared with the long period of its use ; but long before angular or trigo- nometrical surveying had been presented as the only rational method, the variable susceptibility of the needle to magnetic influences had been the subject of investigation and discussion important to the mining engineer, who had no alternative in localities of strong attraction but the use of the very instrument most affected thereby. The earliest astronomical observations to determine the secular variation were made in Paris in 1541, when the needle pointed 7 E. of N". By 1580 it had reached a maximum of 11 80', when it began to recede, reaching the The Compass- Protractor afc used for Mine-Surveys. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 11 true meridian in 1666. The yearly variation then became westward until 1814, when a maximum of 22 34' was attained ! Bennett H. Brough says : " There can be no doubt that in times past a neglect of this variation has led to errors involving great loss and serious danger Regular observations were not made until the middle of the seventeenth century ; but there is a pas- sage (which, however, is so obscure that its meaning is doubtful), apparently re- ferring to the declination of the needle, in the oldest treatise on mining, an ex- tremely scarce work, written in German and published in 1505. No copy of the first edition of this ' well arranged and useful little book,' as the anonymous author calls it, is known to exist." In 1763 Isaac Prince, of Bonsai, in his Miner's Guide or Com- plete Miner, says, with respect to magnetic surveying : 11 The knowledge of ye quantity of this Declination, which is pretty near ye same one year as another and sometimes differs very little for many years together, enables us to adjust ye Needle in such a manner as if it had no Inclination at all. Though ye knowledge of this Inclination has hitherto been fruitless, it is to be hoped yt some time or another some advantage or profit may be discovered by its regularity."* Annual and diurnal variations were also studied and dealt with as intelligently as the time and place permitted ; but general efforts to remedy the er- ratic and deceptive demeanor of FlG - the needle in the presence of iron finally resulted in the invention and introduction in Germany of the Eisenscheibe or iron disk. The first forms of this instru- ment were described in the third edition of Yoigtel (1713), though L. C. Strum, of Frankfort, had proposed the use of the astrola- bium for the miner as early as ITlO.f Fig. 9 represents the de- sign of J. G. Studer, of Freiberg, which is somewhat of an improvement over the original forms, though its principal features are the same. The disk, as will be noticed, was graduated, like the compass of that day, into * Quoted from Cantor Lectures on Mine-Surveying, B. H. Brough, London, 1892, p. 9, in Surveying by the True Meridian, E. W. Newton, F.G.S., Falmouth, 1895. f Vier Kurz Abhandlungen, Leon. Chr. Strum, Frankfurt, 1710. 12 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. twenty-four hours, the twelfth hour marking the !NT. and S. cardinal points. In conducting a survey by its use, two, and preferably three, instruments were employed; one being set up at each adjacent station. The indicator-arms were then tied together with a stout cord, first on one side, then on the other, observing the interior angles. In the same way the angles of inclination on the vertical arc were noted ; and then the last instrument was brought forward to establish a new station. Later, each hour was subdivided into fifteen equal parts, so that each division corresponded to a degree of the sexagesimal system, making it, as compared with the compass, a most reliable instrument for this work ; indeed, it is con- FIG. 10. FIG. 11. Modern Swedish Mine-Tripod and Alidade. sidered by German authorities to be the predecessor of the per- fect mine-theodolite now in general use. The same feeling seems to have prevailed also in Sweden, where we find mining engineers, near the beginning of the nineteenth century,* discarding the compass entirely in their magnetic iron-mines, and substituting the graphic method of conducting mine-surveys by plane-tables of a peculiar make, which, with rare exceptions, has been in use ever since. The invention of the plane-table is generally attributed to Prae- torius in 1537; but Leonhard Zubler, in the first published ac- count of it (1625), credits its origin to Eberhard, a stone-mason. * Handladning uti Svemka Markscheidereit, Horneman, Stockholm, 1802 ; also, Reise durch Skandinavien, J. F. L. Hausrnann, Gottingen, 1811-19, vol. v., pp. 115- 126. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 13 "Who introduced it into Sweden for mine-surveys, Prof. denstrom is unable to determine; but the earliest instruments, no doubt, were of rude construction, with only a sighted ali- dade. I present here (Figs. 10 and 11) a modern tripod, show- ing the clamping-ring by which the paper is held in position while receiving the plot. The telescopic alidade does not differ from those in general use in other countries for surface-work, except that its vertical circle is full, reading to minutes, and the base-rule that carries the bubbles has the linear subdivisions engraved along the edge. The Rapid Traverser of Henderson, of Truro, Cornwall, in- troduced in 1892, is very similar to this mode of construction, except that its alidade is pivoted at the center, instead of being free to move in any position. The survey cannot be plotted in the field, as by the Swedish method. Disks of celluloid, or pref- erably white enameled zinc, are employed, and the direction of each course or draught is marked upon one of the five con- centric circles engraved upon its surface. This instrument and method, it seems, will eventually supersede in Cornwall such magnetic surveys as caused the recent casualty in Wheal Owles mine at St. Just. The magnetometer of Prof. Robert Thalen of Upsala and that of Tiberg are the only other Swedish instruments that have come to the writer's notice. Thalen's is called a simplified modification of the magnetic theodolite of Dr. Lamont;* but in reality the association is very remote, consisting only in the so-called sinus-method of using it, which has been borrowed from Lamont. f It is a simple compass-instrument, having a magnet upon an arm in the line of sight, so arranged that, by its application and removal at the proper time, the azimuth of each course is obtained. Tiberg's (1880) is almost identical with this, except that the compass-box is set in bearings upon low standards, and occa- sionally made to revolve in a vertical position for use as a dip- needle, in determining the location of magnetic ore-deposits. In Warmlander Annaler of 1888, Mr. Sjogren describes some * L' Industrie Miniere de la Suede, G. Nordenstrom, p. 22. (A translation of the methods here described occurs in Mines and Minerals, Scranton, Pa., November, 1898.) f Sur la recherche des Mines defer a Vaide de mesures magnetiques, E. Thalen, 1877. 14 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. very creditable work of this kind, done with Tiberg's instru- ment at Persberg. In England the magnetic needle and Houghton's methods were adhered to, amid recurring failures and disasters, with a loyalty that prevails even to-day in some parts of Cornwall.* In 1778 Dr. W. Pryce declared that methods similar to Houghton's were still in vogue, f He says : FIG. 12. Old English Miners' Dial. * ' The instruments used are a compass without gnomon or style but a center- pin projecting from the center of the compass to loop a line to, or stick a candle upon, fixed in a box exactly true and level with its surface, about 6, 8 or 9 inches square, nicely glazed with a strong white glass, and a cover suitable to it hung square and level with the upper part of the instrument ; a 24-inch gauge or two-foot rule and a string or small cord with a plummet at the end of it ; a little stool to place the dial horizontally ; and pegs and pins of wood, a piece of chalk, and pen, ink and paper." Later (about 1785), extended sights were added; the little three-legged stool no doubt became the tripod ; and, with one or two other slight improvements, we have in England, just * Proc. Royal Cornwall Polyt. Soc., 1893. f Mineralogia Cbrnubiensis, W. Pryce, London, 1778, pp. 202-213. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 15 FIG. 13. before the beginning of this century, the type of dial shown in Fig. 12, in a modernized form, as made by W. F. Stanley, of London. "Who is responsible for its conception as a whole is not known probably no one particular person, as too many years were required to bring it to even its original simple con- struction ; but Adams must have im- proved upon it; since an instrument similar to this is described in his Geomet- rical Essays of 1803. It originally had no bubbles, but was considered level when the needle floated freely. The early makers were, however, in the habit of partly counter-sinking two spirit-levels in the compass-box if de- sired ; but these were not recommended, because, by reason of their small size, they were seldom accurate, and the ope- rator could not test them, or even adjust them if they were known to be untrue. In the English dial shown in Fig. 12 the socket is slotted down on one side (F) so as to permit the limb to be turned vertically, making the sights horizontal. In this position, after the long bubble beneath the compass is made level, the compass-box cover is adjusted and the very small plummet, suspended from its top by a hair or silk thread, is made to read zero on the graduations. The sights can then be tipped up or down, and gra- dients up to 45 can be determined ap- proximately. It will be noticed that the graduated cover, as in most other English dials, has the correction for declivity marked upon it, so as to save the operator any calculation in this par- ticular. Lean began this practice in Cornwall in 1825, receiv- ing a prize of thirty guineas for his borrowed improvement. In 1798 H. C. W. Breithaupt, of Cassel, introduced an instru- ment which may be justly designated the first of mine-theodo- lites. Fig. 13 is reproduced from the original drawings of the inventor by the courtesy of his heirs, F. W. Breithaupt & Son. Breithaupt' s First Mine- Theodolite. 16 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 14. In his book,* Herr Breithaupt described the use of this instru- ment in a new system of surveying, which he himself first prac- tised in the Reichelsdorfer copper-mines of Hesse. Jesse Bamsden had already (1760) constructed a circular dividing-engine in London, in response to the urgent demands of geodetic engineers for circles of greater accuracy than those heretofore graduated by hand; and M. Pierre Vernier, of Bur- gundy, had long since (1631) published in Brussels a descrip- tion of the micrometer-scale which now bears his name. We must note here, parenthetically, that Vernier's scale was ad- justed by hand until Helvetius, the cele- brated astronomer of Danzig, invented, about 1650, the clam p-and-tangent move- ment. Applying these precedents, Breit- haupt circumscribed a compass with a carefully divided circle, read by Ver- nier-plates; invented an arrester that should clamp the needle when not in use ; superimposed an adaptation of the clinometer that was surmounted by a sighting-tube; and supported this com- pact combination upon a sort of tele- scopic tripod-stand, which could be ad- justed for height by means of set-screws at the side. Instead of using two or more instru- ments, as was customary in employing the Eisenscheibe, he de- signed a signal-lamp, two of which were used interchangeably with the instrument. These instruments, which sold for 8 carolin ($33.70), he made himself, and felt the necessity of economy so strongly that he made a plain sighting-tube to take the place of a telescope. In the same year Prof. Guiliani, of Vienna, constructed a mine-instrument which he called a Katageolabium. Like the Graphometer Souterrain of Gen. Komarzewski, it was closely allied to the Eisenscheibe. In England the same spirit of economy and consequent simplicity of construction has always prevailed. In 1796 The Jones Circumferenter. Besehr'eibung eines neuen Markscheidinstruments, Kassel, 1800. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 17 W. & S. Jones, of London, introduced a circumferenter (Fig. 14), which, in addition to the ordinary compass, was provided with a 10-inch brass circle, divided into single degrees and read by the " nonius" as they were then called in England, to 5 minutes of arc. In offering this instrument to the engineering profession, Mr. Jones said : " The error to which an instrument is liable, where the whole dependence is placed on the needle, soon rendered some other invention necessary to measure angles with accuracy ; among these the common theodolite, with four plain sights, took the lead, being simple in construc- tion and easy in use."* It was fitted with one pair of fixed and one pair of movable sights, like Henderson's dial (1869), and "marks the date," says Mr. Newton, " of the first attempt in England to conduct underground surveys, in the presence of iron,- with any de- gree of accuracy." Elliott Bros, made such an instrument for Fen wick in 1822,f but on account of its expense this construction was not much used until Lean began to employ vernier - circles in 1836 in the Cornish mines. So far as available evidence Simple English Theodolite of last Cen- can be relied upon, what is now tnr ^ now commonly known as Lean's T Dial. commonly known as " Lean s dial" was the first telescopic mine-instrument ever introduced; but there is some doubt concerning this fact. Fig. 15 is taken from the Geometrical and Graphical Essays of George Adams, published in 1797. It is there said to be intended as a fair sort of cheap theodolite. Lean's grandson can furnish no authentic information; but it is known that when it was first used in mine- surveys, and made for Captain Lean by the Wilton Works of St. Day, the vertical arc and telescope were removed for common sights and replaced only for surface-work. In accordance with * Adams's Geometrical Essays, revised by Jones, London, 1797, p. 223. f Treatise on Mathematical Instruments) J. F. Heather, London, 1849. 18 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 16. the prevailing custom, the sights alone were used underground. The dial was set up only at alternate stations ; the back- and fore-sights were read with the needle ; and the bearings were assumed to be correct. The centers of vertical shafts simply became intermediate stations; but if an inclined shaft was encountered, a cross-staff was set up in it, so that one pair of sights were directed at a candle-light in the bottom ; then the dial was set up in a drift and made to bear upon the other pair. In this way the magnetic bearing of the shaft was calculated by adding or subtracting 90. "Many miles of dialing have been done," says Franklands, " by this rapid but blindfold method, with no means of closing the survey." It was not thought possible, at that time, to connect the surface and underground surveys by any- thing but magnetic bearings, so that the telescopic attach- ment to the so-called Lean dial can hardly be consid- ered the antecedent of Breit- haupt's first telescopic mine- transit (made in 183 2), though it has been widely used in more recent years for such purposes. Since 1871, E. T. Newton & Son, of Cam- borne, have made the Y's of the telescope interchange- able with the arc or the sights. By thus mounting the tele- scope upon the limb just over the compass-box, the instrument becomes a substitute for the Gravatt level, which has found great favor in the English colonies. It is a recorded fact that the general design of this dial came from the standard model English theodolite, to which it bears a strong resemblance. This instrument is rarely used in Eng- lish collieries on account of its cost; but its construction has long since been such that vertical sights from one side were possible. The prolongation of an inclined shaft alignment, however, can be accomplished only by reversing the telescope in its bearings or by revolving 180 upon its horizontal limb. Seven-inch English Theodolite of Last Century. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 19 Why it is that English engineers adhere to this model has always been a source of wonder to the American profession ; for, in the relationship of the telescope to the vertical circle, it is one of the most extreme of eccentric types. Its retention, however, must be well merited, or it would have been sup- planted by the transit-principle of Ramsden in 1803, or by the concentric model of Sir George Everest (1837), which practi- cally became obsolete twenty years ago. But whatever it has to commend or to disqualify it, the important developments in English engineering-instruments must be followed witb this theodolite. In Gardener's Practical Surveyor (1737) we have de- scriptions of this theodolite r much improved and brought to nearly its present form by Jonathan Sissons, an optician of London (Fig. 16).* It was not perfected, however, until 1760, when Ramsden sensitized its graduated u brain," and John Dolland sent pure light coursing through its telescopic " sonl." Dolland discovered the construction of an achromatic telescope in a compound objective of two kinds of glass (in direct antago- nism to the principles laid down by Sir Isaac Newton), by which both spherical aberration and errors arising from varying refrangibility were in a great measure overcome. While this discovery was very important in the manufacture of geodetic and astronomical instruments, " the most perfect objectives were not made," says Thomas Dick, " until after the improve- ments of Dr. Blair, of Edinborough, Rodgers, of London, and Fraunhofer, of Munich, in the first quarter of this century "f just before telescopic instruments came into general use for mine-work. Lean's dial, then, might have had a practically achromatic telescope. It might also have been provided with a diaphragm and cross-hairs; for Huygens discovered that any object placed in the mutual focus of the two lenses of a Kepler telescope (1611) appeared as distinct and well defined as any distant body. Following this established theory, in 1669 Jean Picard, Marquis Malvasia and others crossed silken fibers in the mutual focus of their astronomical instruments ; and these, while gen- erally acknowledged to be too large for the work required, were * This particular figure represents an instrument made by Kamsden, Jones, Adams, and others, after the general style of Sissons. f The Practical Astronomer, Thomas Dick, LL.D., New York, 1846. 3 20 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 17. Modern English Theodolite. used, in lack of something better, for a century or more. In 1755 Prof. Fontana, of Florence, proposed the use of spider- webs, though it is said they were not put into practical use until Troughton secured for this purpose the webs of the geo- metrical spider, at the in- stance of David Bitten- house, of Philadelphia, who was then constructing the first American telescope. At the time the telescope begins to play some part in the construction of min- ing instruments we find it, so far as possibilities are concerned, a very perfect device; but as the use of fine-quality lenses entailed considerable extra expense, and as almost any contri- vance was considered good enough for surveys in dirty little underground passages, we find at that time generally only poor-quality and low-power telescopes in use. For the precise shaft- and tunnel-work involved in the con- struction of the Great Western Eailway in 1843, Bourne was probably first to use the high-class English theodolite, shown in Fig. 17, in connecting the underground- and surface-surveys through the vertical shafts. Since that time, and doubtless before it, the ideal instrument for nadir-sighting has been considered one in which the vertical axis of the concentric type should be en- larged and perforated sufficiently to per- observations. R Hassler, Superintendent of the U. S. Coast Survey, designed such an instrument (Fig. 18), which, as subsequently improved by General Ibanez, was pronounced by the European Degree-Measuring Commission to FIG. 18. Hassler's Instrument with Perforated Vertical Axis. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 21 FIG. 19. be perfect for the purposes intended.* It had two slow, inde- pendent lateral motions, like the sliding stage of a microscope, by which the cross-hairs could be brought exactly over a point in the aligned base-line to insure perfect parallelism in the sub- sequent setting of the metallic measuring-rod. As its use was restricted to geodetic engineering, it has no special application here, but is inserted only to establish the priority of the invention. Prof. Viertel first used the telescope of an eccentric theod- olite for conducting surveys in vertical shafts, by suspending a plummet through the diop- ter ; but as the instrument was not steady enough, and the plum- met was centered only with great difficulty, the method was aban- doned as impracticable. Prof. A. I^agel, of Dresden, had a nadir-instrument (Fig. 19) constructed without vertical axis, which could be centered over a shaft with great precision by means of a center-plug in the base, which was afterwards re- moved to leave the opening free for the purpose designed. The adjustment of his instrument was the same as that of any or- dinary theodolite. To obtain a true vertical sight he first set a plate of mercury under the tel- escope somewhat below its focal distance. Its surface must necessarily be a perfect horizon, and under a fair illumination will reflect the image of the cross-hairs. When they are brought exactly to coincide with this reflection, the optical axis of the telescope will be truly vertical if it is originally in per- fect adjustment. It was his practice to revolve the telescope 180, and repeat the operation, rectifying any defect at the bottom of the shaft, upon a mechanical stage which was pro- Nagel's Nadir-Instrument. * Die Landmessung, Dr. C. Bohm, p. 605. 22 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 20. vided with co-ordinate micrometer-scales to determine the mean projection. The experiments of both Viertel and Nagel were recorded in Der Cwilingenieur of 1878. In 1876 H. D. Hoskold submitted plans to Trough ton & Simms for a similar instrument; but the plans having been lost in Paris, its introduction in England was allowed to lapse.* This firm, however, in 1885. devised an instrument (Fig. 20) that is very remarkable among the instruments of its class. Its single axis of in Use as a Top-Aux- considerably increased, and the power of the telescope raised to 18 diameters, as shown in Fig. 45. As used for this doable purpose it must be looked upon as the first top-auxiliary, the adjustment of which, for parallelism by means of the base-trivets and for alignment by means of the clamp-and- tangent movement, could be tested and secured by the operator For vertical sighting it has one inconsiderable fault, to be dis- cussed later, which, in comparison with its other admirable features, cannot be justly said to militate against its success- ful operation. The mining-transit shown in Fig. 45, having 4-inch circles, graduated to read minutes, and provided with interchangeable eye-pieces to regulate power and light to suit the conditions, must be regarded as one of the best examples of perfect instrumental construction. In 1885, to meet the ever-prevailing demand for increase^ efficiency combined with smaller weight, Saegmuller introduced 5 52 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. in America the plain detachable object-prism, which was used for a time for vertical sighting, in place of auxiliary telescopes, but was found to be more alluring than satisfactory. When it was simply fitted to the object-glass, like a sun-shade, the 45 mirror it contained reflected rays truly at right angles to the line of sight, but whether or not in absolute vertically was sheer assumption, and the slightest variation from the correct position doubled the deviation of the emergent rays. This was remedied to some extent by setting a small pillar into the collar of the objective, and so attaching small opposing screws to the prism that they could be made to work upon the pillar. In this way the po- FIG. 46. *. . J F sition or the prism could be regulated very care- fully ; but to secure for it absolute vertically was an operation that involved more time and trouble than most engineers are willing to take. Prof. Steinheil, of Mu- nich, first used, in 1847, for astronomical obser- vations, the object-prism attached to a meridian instrument. Later, M. d'Abbadie, of Paris, employed it, rigidly attached to a small traveler's theodolite (Fig. 46), constructed like a Y-level, mounted upon a circle. The vertical limb of his instrument encircled the telescope at the eye-end. In this way the zenith or nadir position of the prism was determined by bringing the vertical circle to read or 180 upon its vernier. Before the objective prism came into use, rays were deflected by means of an ordinary mirror, held in the hand, or by at- taching to the objective collar a mirror-plate, movable upon a hinge, so as to be set at any angle. In this way Borchers con- ducted shaft-surveys in 1844 at Clausthal; but the observation of an object at any but a right angle made the calculations complicated. Last year (1897) Saegmuller brought to perfection the con- THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 53 FIG. 47. Double-reflecting Objective Prism. FIG. 48. struction of the objective prism. His design is intended to utilize the optical law that a ray which has been reflected twice in the same plane makes, after its second reflection, an angle with its original direction equal to twice the angle made by the reflecting surfaces with each other. The double 45 reflecting- prism (Fig. 47), then, will project rays in true vertically when the transit- telescope is placed horizontally, whether the prism be fitted in exact adj ustment or not. Therefore the work of this prism in transmitting vertical sights will be as perfect as it is possible to make the ad- justment of the telescope to horizontal- ity. As used on American instruments, the objective prism now has but one disadvantage. It is obvious that any neces- sary movement of the object- glass in focussing destroys the line of sight, and renders vari- able what should be a fixed eccentricity of collateral sight- ing. Its most successful ope- ration, therefore, is only with the German or French instru- ments, which are focussed by movements of the ocular. The most remarkable of mod- ern applications of the prism to mine-transits abroad is ex- emplified in the instrument (Fig, 48) introduced by Fric Brothers, of Prague, Bohemia, in 1886.* It is claimed by the makers to be an improvement over all other types, to reduce the errors of eccentricity to a minimum, and to overcome the cumbersome features prevalent in most other German instru Fric Mine-Theodolite. Zeitschrifi fur Instrumentenkunde, Berlin, vi., 221, 1886. 54 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 49. ments. The transverse axis of the main telescope is enlarged and perforated in a manner similar to Hohnbaum's Grosses Niveau* so as to 'become a secondary telescope for steep sight- ing. At its outer extremity is rigidly attached a prism, inter- mediate between the objective and ocular, after the fashion of the " broken telescope " of Eeichenbach. It is focussed upon distant objects by a sliding movement of the ocular, as in the mariners' spy-glass, and the barrel is constructed to taper to- wards the eye-piece according to the scientific principle of the convergence of the rays of light in pass- ing through a lens. The sliding ocular contains the diaphragm and cross-hairs, which are protected from moisture on each side by hermetically sealed thin glass disks ; and if by chance any dust- particles should settle upon them, no dif- ficulty is experienced, as the ocular is not focussed upon the plane in which they lie. Spider-webs are hygrometric, being sensibly affected by the humidity of the atmosphere, to the extent of de- ranging the line of collimation. For this reason Fric suggests that, except for the collection of dust and dew, the occasional German practice of using for the diaphragm a thin glass disk, with delicately etched cross-lines upon its surface, should take the place of spider- webs entirely. The main telescope has a focal length of 17 cm., and is provided with a longitudinal bubble, clamped to its upper surface, that must be removed whenever the telescope is to describe a complete revolution. The horizontal circle is made of thick plate-glass. Its gradua- tions are etched somewhat back from its outer edge, and read by means of the Hensold prismatic glass micrometer with the assistance of reflected light from the prism (s) beneath. The needle is placed in a box (M ) outside the standards, to econo- mize space and weight. It is mounted eccentrically at |-th oi Breithaupt's Orientation- Instrument. * Die Geometrischen Instrumente, Hunaus, p. 408. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS, 55 its length from one end, and balanced by a small counter- weight, so as to give the greatest sensitiveness within the avail- able space. We notice here another evidence of the decline in the use of the magnetic needle, though for the work of orientation a very precise instrument was introduced by Breithaupt in 1887* (Fig. 49). The needle in this case, which is of more than ordi- nary length and sensitiveness, is designed to take the place of the magnetometer of Borchers (1846), which was suspended by a silken thread before^ the objective of the telescope and used to determine exactly the magnetic meridian in mines. The most remarkable of such magnetic surveys known to the writer was the extension of the Ernst- August adit-level in the upper Harz,f through a space of 4753 yards, with a final error of only 8 inches in elevation and 1 minute 8 seconds in azimuth. Owing to dense forests between the shafts, their relative posi- tions were deduced from the Ordnance survey in 1876. This is probably the first instance in which any government survey has served as the basis for important underground work. The orientation-instrument can be provided with a vertical circle to adapt it to a wider range of work, or, as made by Tesdorpf, with a side-auxiliary telescope, counterbalanced by a bracket-lamp. As originally built, however, it was intended only as a supplementary instrument. The 15-cm. needle is mounted upon a ruby concentrically with the horizontal circle, and the meridian line of the base is in the same plane with the line of collimation. By use of the additional objective-lens (A) the telescope is transformed to a microscope, and in this way used for the very precise view- ing of the needle. This makes it a superior instrument to those provided with the usual form of striding-compass, the concentricity of which with the instrument is not always reli- able. The striding-compass, as applied to mine-instruments, was first used in Germany in 1837 ; but its original inventor is not known. Brander describes them as early as 1780, in con- nection with sun-dials. In 1889 BufF & Berger introduced it in America with * Der Bergbau, No. 24, 1888; also Cours de Topographic, A. Habets, Liege, 1895. f Berg- und Hilttenm. Zeit., li., 293, Aug. 12, 1892. 56 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. their duplex-bearing mine-transit (Fig 50), as made for George W. Robinson, of Marysville, Mont. In this instrument vertical sighting could be accomplished, with the main telescope in a position that corresponded to the inclined standards of Young, by removing the telescope, with all its adjuncts, from its normal to its secondary bearings, which were very carefully constructed, being, in fact, cast into one piece with the standards. When in this position, a 4-pound counterpoise was attached to the plates at W. Later, Keuffel & Esser, of New York, and Fauth & Co., of Washington, each designed instruments of this class, as illus- FIG. 50. Buff & Berger's Duplex-Bearing Mine-Transit. trated in Figs. 51 and 52, but have found that their construc- tions violated the principles which ought to be observed in a perfect transit>instrument. Such conveniences as they afford are hardly commensurate with the risk of getting the delicately- adjusted bearings full of grit underground while making the transposition. " Besides," says Saegmuller, " the instrument was too heavy and too expensive." His instrument weighed 25 pounds complete. The secondary bearings were not per- manently fixed to the instrument, but contained in side-arms that were attached, when necessary, by thumb-screws to the THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 57 upper part of the standards. To this instrument he added his quick-leveling attachment, patented in 1879. It consisted of two wedge-shaped disks, traveling upon each other in a groove, and interposed between the plates and tripod-head. This, with the quick-leveling heads of Gurley (1878), con- structed upon the principles that obtain in the designs of Pas- torelli and Hoffman-Harden, and the detachable ball-and-socket quick-leveling head of Buff & Berger (1883), represent the American achievements along this line. FIG. 51. Duplex-Bearing Mine-Transit, Keuffel & Esser. The concentric model of mine-instrument with the American supplementary telescope must eventually supersede the types of Borchers and Combes abroad ; but the popularity of the eccentric instrument in Germany still continues. That re- cently made by Ludwig Tesdorpf, of Stuttgart (Fig. 53), is one of the few provided with micrometer-microscopes and detach- able vertical circle. It has a 12-cm. horizontal circle, reading to 1.0", and a 10-cm. vertical circle reading, by vernier, to 1'. 58 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. Between the standards is a circular-box bubble for leveling the instrument, The micrometer-microscope is practically the F IG . 52. original design of Troughton, in which, briefly, the distance be- tween any degree-line and the index of the limb is carefully measured by a sliding scale that passes through the mutual focus of the objective and the ocular. This is operated by a milled-head screw, of such fineness that one revolution corresponds to 10' of arc. Each of the sixty subdivi- sions of the graduated head, then, will represent 10". The instrument shown in Fig. 53 weighs 6 kg., and its tripod as much more. For rapid and accurate sub- tense measurement some engi- neers have for a long time been at work on adapting such mi- crometrical slides to the ocular of the main telescope ; but the results of experiments made in the great Indian survey would seem to confine its use still to the determination of the odd seconds in reading horizontal angles. Prof. Brathuhn has, however, utilized an immovable scale in the diaphragm of the main telescope, on a slightly different principle, that is intended to unite the methods of Dr. Schmidt (p. 34) and the earlier practice of suspending shaft-plumbs in oil and guessing at the probable point of rest* The diaphragm he uses is a glass plate upon which the hori- zontal line is graduated into subdivisions of such value that readings as close as one minute can be estimated. He does not attempt the laborious task of ranging the instrument into exact alignment with the plumb-wires, but sets up at some arbi- trary and convenient station, and, by watching the vibrations of each wire upon the scale, determines its angular position Gea N. Saegmufler Washington. DC Duplex-Bearing Mine-Transit, P^auth & Co. Berg- und Hiittenm. Zeiturtg, Ivi., 395, Nov. 19, 1897. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 59 with reference to the next regularly established station in the survey. The difference of these two readings will give the value of the very acute angle subtended at the instrument from the short base-line between the wires. One of the most interesting of modern German mine-the- odolites is the American pattern of Breithaupt, introduced in 1892 (Fig. 54). It is an improvement upon the generality of American instruments in that the truss-standards (since 1880) have been cast in one piece with the compass-ring; and it pos- sesses also, in the construction of the side-telescope, features well worthy of special comment. FIG. 53. German Eccentric Theodolite. Its spindle-hub is set into a perforation of the transverse axis in very much the same manner as was customary in the first American model, but has a clamping- and tangent-device that holds it securely, and quickly ranges it into alignment with the main telescope, where its position is verified by a longitu- dinal bubble. The illumination is accomplished through the transverse axis, as was first practised by Usser, professor of astronomy, at Dublin, in 1790. The 20-cm. horizontal circle is graduated to read by its verniers, or nonius, as they are still erroneously called by the Germans, to 10". Pedro Nunez, a 60 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 54. Portuguese mathematician, to whom this compliment is paid, published in De Crepusculis Olyssipone, 1542, a proposal that upon the plane of the quadrant be described 44 concentric arcs, divided respectively into from 44 to 89 equal parts. The single indicator, then employed, would coincide more or less perfectly with one of the subdivisions. It gave, no doubt, very close readings. For instance, if the index cut the 7th circle at its 43d gradua- tion, the angle was read as |~| of 90, or 46 4' 17|". The solar on the Breithaupt in- strument, while practically the de- sign of Saegmuller, is one introduced by Prof. Dr. Schmidt in 1892, for the use of American students at Freiberg.* Certain engineers took occasion to point out the possibility that Saeg- muller's solar might move in alti- tude upon its horizontal axis while in use for vertical sighting, and thus destroy the efficiency of the base- trivets. In 1895, Buff & Berger made for George T. Wickes, of Cokedale, Mont., an instrument (Fig. 55) calculated to overcome this objection by making the "polar axis " or vertical pillar rigid with the auxiliary telescope, retain- ing only the trivet-base, in a new form, with every desirable pro- vision to insure parallelism and alignment. As in this construc- tion the setting of the sun's declination becomes impossible, its uses are restricted to the primary offices of a top-auxiliary tele- scope ; but as such, with its delicate, rapid and effectual means for all necessary adjustments, it represents, no doubt, with Breithaupt's side-auxiliary, all that could be required in such individual devices. No matter how perfect may be the construction and means of adjustment, however, each of these appliances has, combined Breithaupt's Mine-Theodolite. ( American Pattern. ) * Oesterr. Zeit. fur Berg- und Hilttenwesen, No. 21, 1892. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 61 FIG. 55. with its advantages, that negative condition known as eccen- tricity, for which correction must be allowed, varying with the conditions in each case. In 1896 the writer designed a mine-tachymeter which, as he ventures to assert, by its peculiar yet simple construction, em- braces the advantages and eliminates the disadvantages of all other types. Its individuality consists principally in the inter- changeability of the auxiliary telescope and the means provided to thus transform the instrument from one condition to the other, as shown in Figs. 56 and 57. In this way the double nega- tive quantities become positive in their resultant, so to speak; and we have a mining-transit capable of performing, with more than usual exactness, all the com- plex functions required in mines, and requiring absolutely no correc- tions for eccentricity. The auxiliary telescope is so provided w r ith a hub of new de- sign that it may be screwed to the threaded extension of either the transverse axis or the vertical pillars of the main tele- scope. In this position it is clamped firmly and ranged quickly into alignment with the main telescope by two small opposing screws that work up an arm of the hub. Upon its diaphragm is but one web, so placed that it shall be vertical when on top, and horizontal when at the side. In either position the amount of eccentricity is the same, though perfect operation would not be affected if this varied, since the observation of steep horizontal angles is made only with the auxiliary on top, and of very precipitous vertical angles with the auxiliary at the side. On this account, any adjustment for parallelism in the op- tical axes of both telescopes is dispensed with, as its peculiar Buff & Berger's Top-Telescope, with Adjusting Trivets. 62 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. adaptability will insure perfect results even if the conditions in FlG 56 this particular are imperfect. I Buff & Berger, who made the instrument, have recently added trivets to the base of the upper vertical pillar; but these are un- necessary, and impair the stability of the instrument. The auxiliary (Fig. 58) has a power of 17 and the main tele- scope of 24 diameters, being the greatest possible under the re- strictions observed with regard to size and light. The amount of light received through the ocular varies as the square of the diam- eter of the objective; therefore, the larger the aperture in mine- transits the more favorable will be the conditions with respect to light, provided, however, that power be not sacrificed by the use of an ill-proportioned ocular. The ocular of this instrument is inverting, conforming to the gen- eral practice of European engi- neers, who no doubt excel in this respect. As American engineers become better acquainted with their desirable qualities, either the Ramsden, Kelner or Steinheil oculars will be more widely used. They all have the advantage of not only permitting greater light and a larger field, but in a tele- scope of the same size an objective Scott's Mine-Tachymeter. Auxiliary of greater focal length is permissi- on T P- ble, thereby favoring the condi- tions imposed to secure the best definition. By thus increasing the focal length of the objective, while, by virtue of its construe- THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 68 tion, that of the inverting ocular is decreased, the magnifying power becomes greater. Both horizontal and vertical circles are 5 inches in diameter, divided into half degrees, and read to minutes. This, on the authority of many years' practice, and by general consent, is conceded to be most easily read underground, and to be fine enough for mine-work. The novice is generally too much in- clined to high telescopic power and extremely fine graduations, FIG. 57. Scott's Mine-Tachy meter. Auxiliary at the Side. with the idea that the greatest accuracy can thus be attained. But this is a mistake. Beside, the stationary double-lens read- ing-glasses that become necessary to read such fine circles only provide the means of invariably burning the engineer's face when he attempts to get both his eye and candle near enough to the plates to take a correct reading. The vertical circle is graduated in quadrants, the zero-line running parallel with the line of collimation, and is read by one double vernier, so placed 64 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. near the eye-end that any angle of elevation or depression may be determined with the telescope in a normal or reversed posi- tion. The horizontal graduations read only in one direction, being numbered continuously with one set of figures, from to 360. This permits the verniers to be single, and provides a uniform method that almost entirely removes any possibility of error in reading, recording, figuring or platting. The verniers are directly under the telescope, so that one need not move to read them, and if the engineer is satisfied that his graduations are correct, he w r ill habitually read but one of these, taking care, however, to repeat every angle at least once ; for no mine- surveyor can be certain of his work until he has checked every step by the same or different means. The U-shaped standards are a new pattern, designed to con- form to American practices and methods. Being of one piece they are very rigid, and, as old-time fancies wear out, will doubtless come into general use. IG ' 58< They are made of aluminum, and bushed with electrum at the bear- ings. Their construction does not permit the use of the usual com- pass-box; but in high-class mine- work the magnetic-needle cannot seriously be said to be essential for -y purpose whatever. The hi, tory of magnetic surveys is itself the death-warrant of the miners' compass ; and in this age of widespread electrical power and lighting (employed with rap- idly increasing frequency in mines), the magnetic needle be- comes no more reliable in mine-surveys than on the present iron-clad man-of-war. Mine-surveys are nearly always figured by trigonometrical functions, as referred to the boundary-lines ; but if the engi- neer prefers to use the calculation by latitudes and departures, a good practice is to establish by stellar or solar observation, at one end of the base-line in the surface-triangulation, or, bet- ter, at one of the boundary-corners, a true meridian from which every station in the whole system, both underground and on the surface, has an established latitude and departure, and every course an established bearing. After the work of procuring THE EVOLUTION OF MINE-SUKVEYING INSTRUMENTS. 65 and tabulating these data is once completed, this system is per- haps the most concise in subsequent computation; but the initial time and effort it requires are scarcely repaid by the benefit secured. For such work, with this tachymeter, the Davis solar screen (Fig. 59) is doubtless best to use. It was invented in 1880 by Prof. J. B. Davis, of the University of Michi- gan, who, in writing to me, said : " In my opinion, my solar screen requires less calcu- ' lation than any other, if properly used. Its work is even more precise than the circles of the transit, and requires no special ad- justments or mechanical conditions. Some others require those that cannot be tested." If used with an erecting telescope, the full aperture of the objective is utilized; but with an inverting ocular, in order to obtain Davis Solar Screen, a clear reflection of the cross-hairs upon the screen, a telescope-cap is provided, so as to reduce the aperture to about J-inch. The diaphragm of this instrument is made of more than ordinary thickness. Upon one side are placed the usual cross- hairs and upon the other the fixed stadia-hairs, which are out of focus when not in use. In this way, as explained before (p. 42), there will be no danger of reading an important vertical angle on a long and indistinct sight with the wrong horizontal hair. The shortest sight possible with the telescope of this mine- tachymeter is 5.5 feet, which for ordinary mine-work is suf- ficient, though occasionally a shorter sight than this is una- voidable. In most German and French instruments the ocular can be drawn out so far as to permit observations within the first meter; but this plan is impossible in American and English models. For these, then, the only plausible plan for very near sighting must provide for an additional objective lens, as described in connection with Breithaupt's orientation instru- ment (see A, Fig. 49). Such an arrangement Buff & Berger are now perfecting for this work. It is provided with ad- justing-screws at the side, so that the center of the lens may be made to coincide exactly with the optical axis of the telescope. 66 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. Otherwise, by the careless addition of an extra objective, the adjustment of the line of collimation may be disturbed. In designing the mine-tachymeter, it was the writer's object to FIG. The First American Transit, built by Young & Son, Philadelphia, 1831. make it the most complete, convenient, precise and compact in- strument yet introduced for mining engineering, and to this end it was his intention to add one other improvement, which THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 67 up to this time remains but a suggestion ; but such engineers or makers as choose to employ it may do so without fear of in- terference, as the original makers are now seemingly extinct. In the Eng. and Min. Journal of November 7, 1891, is de- scribed Cook's patent luminous level tube, which has an inner coating of phosphorescent compound, covered by a coat of water-proof lacquer, by which the bubble is made to appear as distinct against the graduations in the tube in the dark as in the light. As it frequently happens that, because the flicker of surrounding lights seems to absorb all dim rays coming from a long, indistinct sight, the engineer prefers to remain in the dark, the use of such a device would enable him to watch his- bubbles while making such observations. In ordinary setting-up, moreover, it seems likely that the work would be greatly facilitated. Fig. 60, a picture of the first American transit, referred to on p. 25, may fitly conclude this paper, showing how much progress has been made in the construction of such instruments since that modest beginning, sixty-seven years ago. The writer invites correspondence upon the topic here dis- cussed, for the purpose of rectifying possible errors and en- larging the historical evidence, which is now of necessity in- complete. The subject has been profusely treated abroad, and ought to receive more consideration on this side of the Atlantic. 68 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. DISCUSSION. SECRETARY'S NOTE. The foregoing paper aroused so much interest among mining engineers and manufacturers of survey- ing instruments, that the Institute has already been favored with the following painstaking contributions by way of discus- sion, addressed either to the author or to the Secretary. The subject is by no means exhausted, nor can it be; for, aside from chronicling the past, doubtless new improvements will still continue to deserve to be recorded. Nevertheless, the present volume must necessarily stop somewhere. The Trans- actions^ however, will always be hospitably open to further papers on the subject. Decision as to the propriety, pertinency and value of communications offered rests with the Council of the Institute ; but ordinarily those of members would take pre- cedence. Manufacturers' descriptions of their instruments will not be excluded; except that pure advertisements, asserting without defining the merits of special devices, would, of course, be declined. BENNETT H. BROUGH :* Having devoted many years to a study of the history of mine-surveying, some of the results of which I published partly in a course of lecturesf delivered be- fore the Society of Arts in 1892, and partly in a separate work,J I consider that the information Mr. Scott has got to- gether to illustrate the gradual evolution of American mine- surveying instruments during the past sixty-seven years forms a valuable contribution to knowledge. There are, however, sev- eral statements in the paper that are open to criticism. For example, the author is inaccurate in stating that the use of the compass in mine-surveys is first described by Agricola. As a matter of fact, it is described in the oldest treatise on mining, a work written in German and published anonymously in 1505 * Formerly Instructor in Mine Surveying, Eoyal School of Mines ; Sec' y Iron and Steel Institute, 28 Victoria Street, London, England. This communication was received January 23, 1899. f Cantor Lectures on Mine Surveying, by B. H. Brough, London, 1892. | A Realise on Mine Surveying, by B. H. Brough, London and Philadelphia ; 1st edition, 1888 ; 7th edition, 1899. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 69 under the title of Ein wolgeordent un nutzlicTi biiMin wie man Bergwerck suchen und finden soil. The wood-cut of the miner's compass there published shows the dial divided into twice twelve hours. In the library of the Freiberg Mining Academy there are copies of four editions of this rare and interesting book. Of the edition of 1505 only two or three copies are known. A compass similar to that found at Neudorf, described in the paper, is exhibited in Florence. It belonged to Galileo. A study of the history of surveying-instruments shows that in many cases inventions have been anticipated in a curious manner. Thus, the ingenious Rapid Traverser, invented by Captain Henderson in 1892, is, I find, very similar to an instru- ment invented by Brigadier-General James Douglas, and de- scribed by him in 1727, in a work entitled The Surveyor's Ut- most Desire Fulfilled, or the Art of Planometry, Lorigim,etry and Altimetry, brought to its greatest Perfection by the Help of the Un- graduated Instrument, called the Infallible (London : Printed for John Osborne and Thomas Longman at the Ship in Pater- noster-row, MDCCXXVII.). The instrument is thus described : "It only consists of two Pieces, viz., A and B, whereof A is a square Copper Plate, with two moving visual Eulers turning round upon the central Screw Nail D, passing through the Middle of the Plate A. It is furnished at each Corner with a thin Piece of Brass, which may be taken off and on at pleasure, each being pierced to receive headless Pins, which are soldred fast to the Plate ; the four Screws are to make their Plates hold fast the Paper when properly folded at the Corners of the Instrument. To fit the Instrument for Use, first cover the Plate A with a double Sheet of -clean Paper. Then B, your Ball and Socket, is to be joined by putting the Screw Nail thereof through the central Hole of the Plate A, gently piercing the Paper ; which done, apply the two visual Bulers, and screw them fast with the middle Screw Nail so that the said Kulers move easily about the centre : and thus is your Infallible prepared for Use." To those unacquainted with the delicate magnetic instru- ments used in Sweden for discovering iron-ores, the author's description of Thalen's magnetometer and Tiberg's inclination- balance as being almost identical will be misleading. These instruments, which should hardly be classed with ordinary mine-surveying instruments, were described in a paper on ex- ploring for iron-ore with the magnetic needle, which I com- municated to the Iron and Steel Institute in 1887, and were admirably illustrated in the important monograph read at the Stockholm meeting of that Society in 1898 by Professor G. Nordenstrom. For some years past a combination of the two 70 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. instruments has been found most suitable for magnetic explora- tions. Surely Mr. Scott is mistaken in ascribing the introduction of the instrument shown in Fig. 14 to W. and S. Jones in 1796. I have in my possession a graphometer of precisely similar design, made at Brunswick in 1630 ; and graphometers of even earlier date are exhibited in the collection of astro- labes in the South Kensington Museum. The instrument ap- pears to have been invented by Jan Pieterszoon Dou, of Leyden, in 1612, and described by him in 1620. These graphometers, being made prior to the invention of the vernier in 1631,* are of interest in being furnished with the nonius, or variously di- vided auxiliary quadrants, invented by Pedro Nunez in 1542. Referring to Mr. Scott's statement that a diaphragm and cross-hairs in the focus of surveying-instruments were first used in 1669, I may point out that Professor E. Hammer has shown that this was first done about the year 1640, in England, by William Gascoigne, who fell, in 1644, at the age of twenty- four, in the battle of Marston Moor. He used hair and thread for this purpose thirty years before Picard and Malvasia. In the middle of the last century glass and mica plates, with en- graved lines, were first used in place of cross-hairs. They were described by Brander in 1772, and were used by Breithaupt in 1780. Spiders' webs were not used until 1775. Credit for the first application of the tacheometric principle in surveying is given by the author to "William Green, who was awarded a premium for its invention by the Society of Arts in 1778. This view I adopted in a paper on tacheometry, com- municated to the Institution of Civil Engineers in 1888. It has, however, recently been shown by Mr. J. L. Van Ornum, in a scholarly memoir published by the University of Wiscon- sin, that, although in 1778 the Danish Academy of Sciences awarded a prize to G. F. Brander for a similar device, which he had applied to his plane-table six years before, its real dis- coverer was James Watt, who used it in 1771 for measuring distances in the surveys for the Tarbert and Crinan canals. In James Patrick Muirhead's life of James Watt is found a state- * The vernier was invented by Capt. Pierre Vernier, a native of Burgundy, serving the King of Spain in the Netherlands. The Germans seem to have used the Teutonic form " Werner." See Bauernfeind's Elementeder Vermessungskunde, 7th ed., Munich, 1889, p. 124. K. W. E. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 71 ment by Watt himself that he constructed the instrument in 1770, and that in 1772 he showed it to Smeaton. It is interesting to compare the perfect method of measuring lengths by means of the American steel tapes, referred to by the author, with that formerly employed. In an old German work on surveying by Jacob Koebel, published at Frankfort in 1570, the unit of length is described somewhat as follows : " A rood should, by the right and lawful way, and in accord- ance with scientific usage, be made thus : Sixteen men, short and tall, one after the other, as they come out of church, should place each a shoe in one line; and if you take a length of exactly 16 of these shoes, that length shall be a true rood." This description is accompanied by a quaint illustration show- ing the process being put in operation.* MR. SCOTT : Mr. Newton had sent me an electrotype of Hen- derson's Rapid Traverser to accompany the text in my article which relates to it, but it was confiscated by our Government officials because the 'importation of small articles of merchan- dise through the mails has been unjustly prohibited by the Uni- versal Postal Union Convention. I cannot let Mr. Brough's description of the " Infallible " go by without citing one other of the progenitors of Capt. Hen- derson's Traverser, to which Adams has made casual reference in his Essays, the first edition of which was published in 1791. He says : "Mr. Searle contrived a plain table, whose size (which renders it convenient, while it multiplies every error) is only five inches square, and consists of two parts, the table and the frame ; the frame, as usual, to tighten the paper observed upon. In the center of the table is a screWj on which the index sight turns ; this screw is tightened after taking an observation." I did not wish to convey the impression that Jones' circum- ferentor (Fig. 14) was unquestionably the first of its kind in England, unless what Mr. Newton had ventured to say con- cerning it would tend to establish that fact. Possibly even Mr. Newton may be incorrect, for an old English workf has this interesting paragraph : * Geometrey von Kunstlichem Feldmessen. A copy of this rare book in the Astor Library, New York, is dated 1593. The edition of 1570, cited by Mr. Brough, is in the British Museum. E. W. K. f Geodesia, or the Art of Surveying, John Love, London, 1744, p. 59. 72 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. " This last instrument depends wholly upon the Needle for taking of angles, which often proves erroneous ; the Needle yearly of itself varying from the true North, if there be no Iron Mines in the Earth, or other Accident to draw it aside, which in mountainous Lands are often found : It is therefore the best Way for the Surveyor, where he possibly can, to take his Angles without the help of the Needle, as is before shewed by the Semicircle. But in all Lands it cannot be done, but we must sometimes make use of the Needle, without exceeding great trouble, as in the thick woods of Jamaica, Carolina, &c. It is good therefore to have an Instru- ment with which an Angle in the Field may be taken either with or without the Needle, as is the Semicircle, than which I know no better Instrument for the Sur- veyor's Use yet made publick." The semicircle Love describes had fixed and movable sights, though divided very coarsely; for in the preface of his work he " I have taken Example from Mr. Ho well to make the table of Sines and Tan- gents but to every fifth minute, that being nigh enough in all Sence and Reason for the Surveyor's Use ; for there is no man, with the best instrument that was ever made, can take an angle in the Field nigher, if so nigh, as to five Minutes. >r I have recently secured a copy of Prof. Van Ornum's paper on " Topographical Surveys,"* and am glad to ascribe to Watt the honor that seems justly due him in having been first to use subtense measurement in the construction-work on the Scottish canals. I had found a record of this fact,f but without dates or farther detail. From this Bulletin I wish also to supplement my remarks on the plane-table, and reproduce here the description and cut of the original instrument (mentioned on p. 12), for the benefit of the many who have not had the pleasure of reading the paper. Prof. Van Ornum says, in part : "To Johann Prsetorius, the renowned mathematician, professor and savant, prolific in writings and inventor of many mathematical instruments, is definitely credited the invention of the plane table in 1590. To enable the engineer to un- derstand the famous Praetorian Mensula, and to appreciate its peculiarities and principles of construction, Prof. Carl Dziatzko, of the University of Gottingen, Germany, has sent the accompanying cut (Fig. 61) and description, which were taken from M. Daniel Schwenter's Geometria Practica, Niirnberg, 1667. A B C D is a plane board about 15 inches square and 1 inch thick, having two cleats on the edges to prevent it from warping. In the corner is a compass, E, in a square box, having a sliding lid, so that it can be opened and shut at pleasure. A spirit-level (not shown) is necessary. G is a wooden screw, the bottom threaded, and the top * Bulletin of the University of Wisconsin, Engineering Series, vol. 1, No. 10, Dec., 1896, pp. 331-369. f Inventors and Discoverers in Science and Useful Arts, John Timbs, F.S.A., N. Y., 1860, p. 287. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 73 having a square head. There is a nut, H, at the bottom. In the center of the board is a square hole, into which the wooden screw G is glued. K I is a hard- wood piece, with a round hole at I, through which the screw, G H, passes. To K a triangular piece, L, is nailed. On three sides of this piece three wooden screws, M, N, O, are glued, and three nuts, P, Q, E, made for them. Three pieces, S, T, V, 5 to 5 feet long, are made to fit these screws, M, N, O, thus forming the tri- FIG. 61. The Prsetorian Mensula. pod. A graduated brass scale, W, 14 inches long by 1 inch wide, forms what is called the chief scale. A semicircular piece of brass, a, is left at one end, and a hole made in it on the edge of the rule so that a fine needle can be passed through it. Six inches from this a similar piece, 6, is left. Two sights, e and/, are made. The sight e has three fine holes perpendicular to the edge of the scale and in a plane with it. The sight/ has a hole cut in it, and a fine wire or thread stretched 74 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. across it in the plane of and perpendicular to the edge of the scale. These sights are made so that they can be turned up or down. Three other brass rules, X, Y, Z, similarly graduated, are called the side rules. The first rule, Z, is f of an inch wide and 1 foot long, and is fastened rigidly to the cleat B C, so that the edge of it is in the middle of the cleat. The second rule, Y, is similar to Z, but has, be- sides, a semicircular piece of brass fastened to one end, with a hole in it. A screw, g, fits in this hole and the rule is fastened to the cleat B C,- so that it coincides with the rule Z. This rule turns about the screw g, and has two sights, the same as the chief rule. The third rule, X, is 9 inches long and is soldered to a square piece of brass, so that when it is fastened to the table it will be perpendicular to the rule Z. The point where the top edge of Z crosses this rule is taken as the zero of its scale. A rule, n i, with the plumb-bob k attached, is used for centering the table over a point in the field. A target, q, r, s; triangle, /; square, t; measuring rod, p ; hammer, m, n, o ; compass, v ; proportional dividers, x ; and rule, u, complete the secondary equipment." Such instruments as this were doubtless the first to be used in the Swedish mines; and where I have said (p. 13) that they were rude I FIG. 62. Plane Table Described by Simms. wish to substitute the asser- tion that they were very complete, if we may judge by the little room there has been found for improvement up to com- paratively recent times. In the latter part of the eighteenth century Mr. Beighton had used a plane-table with a tele- scopic alidade, in which the telescope was placed at one end and a coun- ter-weight at the other. The instrument shown in Fig. 62, which is taken from a standard English work,* represents the construc- tion in general use about 1840. The author says : "It is a board, A, about 16 inches square, having its upper edges rabbeted to receive a box-wood frame, B, which being accurately fitted can be placed on the board in any position with either face upwards. This frame is intended both to stretch and retain the drawing-paper upon the board, which it does by being sim- ply pressed down into its place upon the paper, which for the purpose must be cut a little larger than the board. One face of the frame is divided into 360 from * A Treatise on Mathematical Instruments, F. W. Simms, F.K.A.S., London, 1834-1844. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 63. the center, C, fixed in the middle of the board, and these are subdivided each way as minutely as the size of the table will admit. The object of these graduations is to make the plane table supply the place of the theodolite, and an instrument formerly in use called a semicircle. "There is sometimes a second center-piece, D, fixed on the table at about one- quarter of its width, from one of the sides and exactly half its length in the other direction. " To the under side is attached a center-support with ball-and-socket or parallel plate-screws, by which it can be placed upon a staff-head, and made to sit hori- zontal by means of a circular spirit-level." The author says, further, that the box-wood frame and its graduations could be dispensed with entirely, and that the ex- pedition with which certain field-work may be performed by a person who is expert in its use is its chief recommendation. "W. F. STANLEY* (communication to author) : I wish to ac- knowledge with thanks a copy of your article, and to express my pleasure with the extent of your research. In the preparation of my work I spent some months along these lines, but only par- tially succeeded; therefore, I know the trouble. What you have said concerning Fig. 40 I believe to be in- disputable facts, but I beg leave now to submit a des- cription of an instrument (Fig. 63) which I completed in the latter part of last year (1898), just as your paper was going to press. It is the first dial of the Hedley style, I believe, which may be used Stanle 7' s Latest Improved Hedley-Dial. for sighting in true verticality. The Hedley ring did not per- mit this ; but, by remodeling into a sort of cradle, this diffi- culty is avoided. The vertical limb is now a complete circle, and graduated to read on the upper half from to 90, in minutes of arc', each way. In the lower arm of its vernier is Math. Instrument Maker, 4 and 5 Gt. Turnstile, London, England. 76 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. an index, which is used to indicate the correction in hypothe- nuse and base, as marked on the lower half of the circle. The horizontal limh is graduated outside, as shown, and reads to minutes by double opposite verniers, placed so as to be -coin- cident with the line of sight. The diaphragm of the telescope is provided with platino- iridium points for subtense measurement, as described in my work,* p. 128. This alloy has about the hardness of spring- tempered steel, and is, as far as known, perfectly non-corrosive in air or moisture. We have found that this point-reading is more exact than with the web, as irradiation, due to the edge- reading of the web, is entirely avoided. The growing sentiment in England is greatly in favor of 3 leveling-screws, but I do not think mine-surveying so exact as surface, and the strain put upon the axis by the use of 4 level- ing-screws is unimportant, and otherwise much minimized by the springiness of the Hoffman-Harden tripod head. The great difficulty with our engineers here is to get head-room in the shallow workings of our coal-mines, and it was for this reason that I designed the prismatic dial you have illustrated in Fig. 41. On account of its apparent height your mine tachymeter would not be received favorably in this country. The dial here described has been built as low as the conditions will permit, and seems to answer in many mines, though, as I say, there are obvious reasons why it should be still lower. Its total height, including the 3J-inch tripod head, is 10 inches, and it weighs 8J pounds. MR. SCOTT : The height of my instrument is not so great as it would seem by a casual inspection of Fig. 56. The stand- ards are purposely made a little higher than is usual, so that, with a full aperture of the telescope, it can be made to observe objects in dips up to about 55, and as great as 63 with about one-quarter of the diameter of the objective above the plates. They are, however, no higher than is necessary to effect conve- niently the complete revolution of the 9J-inch main telescope and the partial revolution with the 5J-inch auxiliary telescope * Surveying and Leveling Instruments, W. F. Stanley, London, 2d ed., 1895. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 77 .FiG. 64. attached. When the interchangeable auxiliary is placed on top, the total height from the tripod-head in the 5-inch model is 14 inches, and the total weight 12 pounds, or 5.5 kilo- grammes. C. L. BERGER & SONS* (communication to author) : After much difficulty and delay we have been enabled to secure a photograph of the nadir instrument (Fig. 64), to which you have referred on p. 701. It was designed by our Mr. C. L. Berger to carry the alignment of the Dorchester Bay sewer very accurately down through the westernmost of the three shafts sunk upon it in driving its entire length of 6090 feet. The lower part of the cast-iron stand rests upon three supports, the two forward being con- trived to act as leveling-screws, the rear one being merely a stationary swivel-point upon which the upper part is made to move slightly in azimuth by means of the opposing tangent- screws shown acting against two small pillars near the base of the Y-standards. When the desired position is thus attained, the base is clamped by means of the set- screws or nuts shown in the forward part on each side. The adjusting block, usually set into the bearing of the horizontal axis, was dispensed with in this case, as the adjustment could be secured by means of the leveling- screws and a delicate striding-leyel provided for that purpose.' The telescope had a 2-inch aperture, a focal length of about Nadir " Crafts in * Math. Instrument Makers, Successors to Buff & Berger, 9 Province Court, Boston, Mass. 78 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 20 inches, and a power of about 40 diameters. As in all tele- scopes of this length and size, the focusing arrangement is placed at the ocular, where it is always within easy reach. Mr. Stearns, in the paper to which you have referred, cor- rectly said : " As the use of a vertical cross-wire would have caused confusion on account of its looking so much like the string, two wires crossing each other, and making a small angle with the vertical, were used instead." The entire weight of this instrument is about 50 pounds. F. W. BREITHAUPT & SOHN* (communication to author) : We have studied very carefully the copy of your work which you sent us. We regret that we have no drawing of the first com- plete telescopic mine-theodolite made by us in 1832 for the Im- perial Brazilian Mining Association of London. The horizontal circle, however, was 5 inches in diameter, di- vided into J and read by verniers to 1 minute of arc, and the ocular provided with a prism for steep upward sighting. We send you a copy of the fourth volume of our Magazin, published in 1860, in which you will find illustrated a mine- theodolite (Fig. 65), the first of its kind in Germany, which we made for the Mine-Surveyor-General of Saarbriicken in 1836, and which Bergingenieur Praediger, in the same year, used in that celebrated survey of 2000 meters in the Ensdorfer tunnel at the Kronprinz coal-mines, near Saarlouis. It will interest your readers to notice the apparatus provided to measure the height of the instrument above the station over which it is set. It was made of five small tubes, one sliding within the other, so as to be convenient to carry about and quickly attached to the hook of the bar that passes down through the head of the tripod. In this position the bottom of the first tube was always 30 inches below the horizontal axis ; the next, when pulled out its full length, 40; the next, 50, etc.; and, finally, the odd inches indicated on the last draw. We call attention also to the way in which the plummet was balanced by a counter-weight a method that does not compare very favorably with the reel- plummets used in your country to-day. The tripods had exten- * Math. Instrument Makers, Established 1760, Cassel, Germany. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 79 FIG. 65. Praediger's Original Instrument of 1836. 80 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. sible legs, and the signal targets were so designed that their centers should correspond with the axis of the instrument in height. FIG. 66. Breithaupt's First Eccentric Mine- Theodolite. In the same magazine is also illustrated the eccentric the- odolite (Fig. 66) in its first form, as it appeared in 1834. Among the advantages claimed for it then may be enumer- ated : 1. It may be used to sight an object in any elevation or de- pression with the single exception where the object is exactly THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 81 vertical above or below the center of the instrument, and this difficulty can be obviated by a little shifting of the object or the set-up point. As a little disadvantage one could mention, the object must be sighted in two different positions of the tel- escope, unless a trigonometrical calculation is made to account for the eccentricity of the telescope ; but this operation is not only convenient but absolutely necessary to compensate for the little imperfections in instrumental construction. All vertical angles are read without correction. 2. The far easier adjustment of the instrument. 3. Diminishing the height of the telescope's axis, which is only 2 inches above the horizontal plates. 4. Greater length of telescopic axis between its supports and larger diameter of vertical circle. 5. The construction is such that the bubble tube on the tele- scope can also be placed to stride the axis for its more accurate adjustment. For convenience, the telescope had a prismatic ocular, and was provided with a reflector to measure altitudes of the sun, for which purpose this theodolite is well adapted. It is also con- venient in sighting the polar star to establish the true meridian. The striding-compass and circular box-bubble are both on top of the instrument, and very easy to observe. We cannot give any authentic information' as to who first used this instrument, but in any event it is quite wrong that Borchers had used it as early as 1835, as you record it on p. 27. He was not employed at Clausthal until 1841.* At that time he found there, in the Royal Mining Academy, a theodo- lite of our make, which was not intended, or properly designed, for mine-surveying. With it, however, he conducted a mine- survey, the results of which were so satisfactory that he was led in March, 1842, to order a theodolite, which we delivered in May, 1844. We regret that we have no presentable illus- tration ; but concerning it, we will say that the vertical circle was divided into J and read by opposite verniers to minutes. The horizontal circle was 6 inches in diameter, divided into j- on silver and read by verniers to 30". The vernier openings in the covering of the limb were provided with glass plates to * See Der Bergiverksfreund, vol. xiv., p. 419. 82 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. protect them from dust, etc., the invention of which device must be credited to our house in 1835. The telescope was 13 inches long, was reversible upon its horizontal axis through the standards, and provided with a bubble-tube that could be turned to the line of sight. There was also a striding-compass, but the special feature was the reflector arrangement fixed to the objective, to which you have referred on p. 52 of your work. This reflecting mirror moved in a small graduated arc, upon which it could be clamped in any convenient or desirable posi- tion, and the exact value of the deflection-angle read by a small vernier provided for the purpose. Borchers had this concentric instrument in commission until 1856. On June 10, 1850, 'the great Ernst- August tunnel was begun, and the first holing was made in 1856. Then, on ac- count of the work to be done in inclined shafts, Borchers had an eccentric theodolite made by Meyerstein, very much as you have shown on p. 26. PROF. DR. MAX SCHMIDT* (communication to author) : As your work deals only incidentally with the catageolabium of F 67 Giuliani, I shall be glad to supplement it at your solicitation with the best des- cription it has been possible for me to prepare in the short time I have had at my disposal for this purpose. On p. 79, Section 91 of his work, Giuliani says : " If I were a mine-surveyor I would use an in- strument shown in Fig. 2, Plate V. (here repro- duced in Fig. 67), which corresponds in its prin- cipal parts with Brander's Scheibeninstrument. I will call it Catageolabium^ as it serves for subterra- nean measurement." Here follows his description, from which it appears that the circle had a Prof. Giuliani's Catageola- Diameter of 14 or 15 inches and was di- vided into 24 hours of 60 minutes each. It had two verniers, by which the hour-minutes were divided * Vorstand des Geodetischen Institute der Konigl. Technischen Hochschule, Miin- chen, Germany. t Constructed from the Greek words Kara, downward through, yfj, earth, and Aa/3iv, to take or to measure. SCOTT. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 83 into 15 parts. On the alidade there was a small circular box- bubble and compass. The vertical arc was of 6-inch radius, and provided with one vernier, by which each degree of arc could be read to 2 minutes. Upon this vertical arc was a tube sup- ported by two pillars of such length " that the tube can see beyond the plate in very precipitous angles " (this is, therefore, certainly the first top-telescope) ; " but the discomfort experi- enced with these precipitous angles by being obliged to hold the head so far back or so far forward over the plate in order to get the eye to the tube is avoided by unscrewing the front part of the tube and substituting another small tube bent at a FIG. 68. One of the Oldest-known Broken-Telescopes. right angle and provided with a 45 reflector." (This is the first broken-telescope that I know of.) Another very old broken-telescope is shown in the accom- panying illustration (Fig. 68). It is one made by an unknown mechanic, though from the metal work and workmanship I should say that it came from the shop of Hoeschel the son-in- law of Brander somewhere between the years 1800 and 1810. The objective is achromatic and of Fraunhofer's design. The instrument consists of only a vertical circle, a broken-telescope and a telescope-bubble of Brander's pattern. It is now in the possession of the geodetic department of the Royal Technical Academy Hochsckule) of Munich. 84 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FIG. 69. Another of the earliest types of these instruments which I have in my collection was probably made by Utzschneider & Fraunhofer, but in what year I do not know. The striding- bubble it now possesses has been added recently, as well as the micrometer-screws and verniers of the vertical circle. But the telescope, the horizontal circle, the tripod base and the arms which support the reading-glasses remain unchanged. . I send also another illustration (Fig. 69) of the Scheibenin- strument of Hoeschel as modified by Oberbergrath von Yoith in Amberg, and described in his work.* The illustration shows a theodolite of Hoeschel as it was duplicated in 1792, for the Bavarian Academy of Sci- ence, for a land-survey. To adapt this theodolite for mine- surveys, von Yoith (in 1805) replaced the telescope with a diopter-tube, while the micro- meter-screws for the measure- ment of angles remained un- changed. This instrument was also provided with a single ver- nier at one end of an alidade, or arm, at the opposite end of which was the clamp and tangent-screw. For mine-sur- veying there were provided signal-lamps, in which the rec- tangular window was marked with a cross. Brander's bub- ble-tube (which was hinged at one end and provided with double-adjusting nuts at the other) occurs again on the vertical arc. To set up the instrument in the mine, v. Yoith used the Hungarian surveying-buck. Komarzewski's instrument is described and illustrated in the Journal des Mines, No. 48, Fructidor, An JTJ(1803). Rapport fait * Vorschldge zur Vervollkommnung der Markscheiderinstrumente, Ignaz v. Voith, Landshut, 1805. Von Voith' s Theodolite. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 85 a rinstitut National des Sciences et des Arts sur un Graphometre souterrain destine a remplacer la boussole dans les mines, as well as in the little work entitled Memoire sur un Graphometre souterrain (a Paris chez Charles Pong ens), which says that the instrument is constructed upon the same principles as the theodolite, and consists of a circular disk, which is placed firmly and in a hori- zontal position by means of a level with a cylindrical air- space. But the illustration is nothing else but the Msenscheibe, a,s it is portrayed in von Oppel, and as it was improved by Studer in Freiberg, for the measurement of vertical as well as horizontal angles, " under the instructions of Krumpel," in 1792.* Komar- zewski made surveys in the mines of Freiberg with this instru- ment between 1795 and 1801. Borchers, while a mining engineer in Clausthal, wrotef that in France mine-surveys were made about 1835 with a the- odolite with eccentric telescope. Reference may be made also to an article by Prof. Combes, Annales des Mines, Series 3, Tome ix., 1836, and to the separate edition, published in the same year, and entitled Sur les leves de plans souterrains, etc. The theodolite as a mining-instrument was described and illustrated in the work of von Hanstadt in 1835; but in the Bergwerksfreund, vol. 14, p. 392 (1851), the Royal Prussian mine surveyor of Saarbriieken says that the use of the theodo- lite had been established in the mines there since 1817. The official records of that district show with certainty that Praediger used a theodolite there in 1835. Two theodolites of this kind, ordered from Breithaupt by the Royal Prussian Ministry of the Interior, were described by Praediger in the JBergwerksfreund in 1836. In the work of GensanneJ is described the Redpiangle ou Graphometre, which, according to the illustration, consists of a half-circle with one set of fixed and one set of movable sights, so that it is nothing else but an astrolabium. Again, the work of Duhamel describes a method entitled Lever de plan d'une Mine avec le Graphometre, etc. * Freiberger gemeinnutzige Nachrichten y 1803, p. 189. f Bergwerksfreund, vol. xiv., No. 40, 1851. J Geometric Souterrain^ M. de Gensanne, Paris, 1770 ; Montpellier, 1776. % Geometric Souterraine, J. P. F. G. Duhamel, Paris, 1787, p. 179. 8b THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. The solar apparatus shown in Fig. 54 was first made in Ger- many by Hildebrand of Freiberg, on an order of Bergingenieur Keller, who w^as then in America, but with improvements sug- gested by me.* MR. SCOTT : Dr. Schmidt may be correct in ranking Giuliani's instrument as the first of broken-telescopes, but I must differ with him in the assertion that in it is to be found the first top- telescope ; for while the sighting tube occupies the same relative position it is in no sense an auxiliary device, or what the Ger- mans call Hiilfsapparat. There is a distinction between an eccentric main telescope and an eccentric auxiliary telescope, and in this comparison it does not matter whether the eccen- tricity occurs at the side or above the center of the instrument. The sighting-tube of Giuliani's instrument is no more to be considered a /op-telescope than that shown in Fig. 66 is to be considered a ^'de-telescope. I could also question the state- ment, but not with the same degree of assurance, that the sight- ing apparatus in the Catageolabium is a broken-telescope at all. It seems to be a simple application of a prism to the eye-piece. In the common acceptation of the term, as I understand it, a broken-telescope is one in which the prism is placed between the ocular and the objective, as I have it in Fig. 68. There seems to be a prevailing opinion that the invention of the broken-telescope belongs to Reichenbach. T. Ertel & Son, his successors, in writing to me, doubtless with reference to the instrument mentioned by Prof. Schmidt (p. 84) as " another of the earliest types," say : " Since our present manager came to the direction of our business he has been able to discover only one of Reichenbach's instruments, which we sold to the Royal Technological Academy. As nearly as could be judged by its appearance it must have been made some time in the first twenty years of this century, but we are not certain that this was the first of its kind." Illustrations of the Eisenscheiben of von Oppel, to which Dr. Schmidt has referred, I reproduce here (Figs. 70 and 71) from my copy of this justly celebrated old work.f On pp. 207-212 he seems to say, in part : * Zeitschr. fur Instrumentenkunde, vol. viii., p. 188. f An leitung zur Markscheidekunst, F. W. von Oppel, Oberberghauptmann in Dres- den, 1749. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. "I divide the Eisenscheiben into two principal kinds, those that give the angle in the common degree of the circle and those which express it in hours, etc. The first kind (Fig. 70), which is graduated into 360, I propose to make as follows: Take a circular brass plate and divide it into four quadrants, each of which is marked with a Roman numeral, as is shown, for distinction. Each quadrant is divided into degrees and numbered each way from the principal zero-line, which is engraved upon the back of the plate as well as upon its face. The index-arm must now be pivoted at the center in perfect concentricity with the plate, and at its outer extremity provided with a ring or hook, to which the measuring chain may be conveniently attached. Then make a stand, the base of which can be screwed to a desired station, and mount the plate upon it by two hinges, so that it FIG. 70. Von Oppel's Eisenscheibe, Style No. 1. can revolve, if necessary, to a horizontal position upon the 90-line. If the small plummet line, which is attached to the center of the upper part of the base, always coincides with the meridian-line that is engraved upon the back, the base will be perfectly horizontal. "The Eisenscheibe, which is divided into hours (Fig. 71) and the subdivisions thereof, I recommend as being just as convenient for use. In a solid brass circular plate, which is hollowed out for the purpose, is inserted a smaller graduated disk, as well as a ring surrounding it, each of which may be revolved about a common center at will without disturbing the position of the other. In the graduated cir- cle the cardinal points (Meridies, Septentrio, Occidens and Oriens) are marked in reversed position as in the compass, and upon the 12th-hour line is securely fast- 88 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. ened a strong brass plate, standing perpendicularly upon it, and holding a brass indicator-arm provided with a hook at its outer end, to which the brass measuring- chain may be attached. The intermediate ring is divided simply into quadrants, and upon its meridian-line are two small blue steel pins to aid in moving it upon a back-sight, where it is clamped by means of small brass pins from beneath. Through the outer plate are bored a few holes, so that the instrument can be securely screwed to any station-point. On each side of the vertical plate are sus- pended small plummets, which determine the horizontality of the setting." FIG. 71. Von Oppel's Eisenscheibe, Style No. 2. D. W. BRUNTON, Denver, Colo, (communication to the Secre- tary) : I have read with care Mr. Scott's most interesting paper, and regret that I have not time to discuss at length some of the many questions it suggests. In Aspen, Leadville, and Red Cliff, Colo., and generally in western mining camps where contact ore-bodies occur, and strip or vertical veins are almost unknown, the favorite (and, to my mind, by all odds the most convenient) instrument is THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 89 Buff and Berger's new high-standard mountain and reconnois- sance transit, with a 4-inch horizontal limb, weighing 6 pounds. In this instrument the tangent-screws are placed at one side, away from the line of sight, and the edge of the horizontal arc is notched as deeply as possible without cutting through the metal. This arrangement, combined with the greater elevation of the standards, permits angles of either elevation or depression up to about. 70 to be read with the ordinary telescope. This is as far as it is ever necessary to go in this region, except on shaft-work, which is always done by plumbing. The great practical objection to instruments with top or side auxiliary telescopes is not that they cannot be brought into adjustment, but that, being elaborate and expensive, they must be carefully FIG. 72. Plan of Brunton's Pocket-Transit Opened for Taking Courses or Horizontal Angles. kept, and therefore are frequently in the office, perhaps several miles away, when occasion for their immediate use arises. At the request of the Secretary, I take pleasure in contribut- ing to this discussion an account of my pocket mine-transit,* manufactured by William Ainsworth & Son, Denver, Colo., and already in use in every country from Australia to Alaska. It is employed in the work of the United States Geological Survey, and the surveys of most of the States and of Canada. Instruction in the use of it is a part of the engineering course at the Lawrence Scientific School, Harvard University, the School of Mines, Columbia University, and a number of the western mining schools. The chief merits of this instrument consist in * Patented September 18, 1894. 90 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. FlG. 73. its extreme portability and the extraordinary rapidity with which reasonably accurate surveying can be performed by its use. Many years ago I began experimenting with the purpose of devising a combination-instrument which would perform all the necessary survey-work required for current daily mining practice and commercial and legal mine-examinations. After constructing six or eight different forms, I hit upon the design now finally adopted, and made arrangements for its manufac- ture with the house above named. The development and in- troduction of this instrument has been with me a labor of love, and not an enterprise looking to commercial profit ; and the same is, to a considerable degree, true of the manufacturers, who 'use the utmost care in the produc- tion of the instrument, and push its sale largely as an indirect advertisement of their chief business, namely, the manu- facture of instruments of precision and high-class balances, in which latter line they have already surpassed nearly all competitors, and achieved the command of the American market. The dimensions of this pocket-transit are 2|- by 2|- by -^|- inches, and the weight (in aluminum case) is 8 ounces. In other words, it is strictly a pocket-in- strument, and is, in fact, carried in the pocket like an ordinary compass, which I it does not exceed in bulk. Yet it does Correct Position in Taking the work of a sighting-compass, a clinom- Courses or Horizontal An- t prismatic compass, and an Abney gles not more than 45 * above or 15 below the or -Locke level, measuring horizontal and Observer. vertical angles, dips, etc., with a high degree of accuracy. I will not enter into detail here as to the manner of its use for all these purposes. The manufacturers will furnish on demand a circular covering these particulars, and a few gen- eral remarks will be sufficient in this place. Fig. 72 is a plan of the transit when opened for taking courses or horizontal angles. It shows a spirit-level, which should be set, for this operation, at right-angles to the line of sight. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 91 Fig. 73 shows the proper method of holding the instrument in taking courses and horizontal angles. The instrument is correctly sighted on the object when the eye, looking into the mirror which lines the lid, sees the black center-line bisecting both the opening in the front sight and the object sighted at; after which, the reading of the needle is comparatively easy if the proper precautions as to position and leveling have been observed. The most important of these is, that the instrument should not be turned in the hands, as is customary with an ordinary compass, but the hands should be held rigidly against the body, which should serve as a tripod for the instrument, and changes of direction should be made by twisting the body to right or left, preserving the level posi- tion as indicated by the bubble. For inclined sights and for taking dips, the bubble-tube (which is easily revolved, by means of a crank on the back of the instrument, with the middle finger of the right hand, while the thumb and fore-finger grasp the instrument) furnishes an accurate reading by means of the vernier attached to it (Fig. 72) and revolving with it. A little practice will enable the engineer to perform with this small pocket-transit work of great variety and surprising accuracy at very little cost of time. In many cases, such a small and portable instrument will be to the engineer a most agreeable change from the numerous old-fashioned contri- vances which it supplants. H. D. HOSKOLD, Buenos Aires, Argentine Republic, S. A.* (communication to the Secretary) : The writer is not aware that any record exists indicating the period when angular and linear measurements were first introduced and practiced as a science, and the form of the instruments employed as auxiliaries in useful astronomical observations and engineering operations for scientific and economic purposes. Still, as previously stated, f he believes that the first instruments were exceedingly rude in construction, and probably consisted for the most part of two * Director of the National Department of Mines and Geology and Inspector General of Mines of the Argentine Republic. This communication was received May 5, 1899. f Trans. Am. Soc. Civ. E., vol. xxx., p. 137, 1893. 92 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. movable cross-bars of wood or metal fixed on the top of a rod, the opposite end of which was thrust into the ground for use ; or some such contrivance may have been placed on a square board in the form of a plane-table. The angles observed and formed by the radial bars may also have been determined in linear measure by applying a simple straight-line divided scale of equal parts, similar in principle to that which was applied to the cross-staff of navigators in 1514,* or by the divided sides of a quadrilateral figure or geometrical square described upon a board. Nevertheless, in the Chaldean records, recently discovered, mention is made of an iron wheel (or circle) constructed some 4000 or 4500 B.C. ; but nothing is said about its use. It is im- portant to note that the late Mr. George Smith, of the British Museum, discovered, prior to 1870, in the ruins of the tile- brick library in the Palace of Sennacherib (704 B.C.), a large fragment of a circular Assyrian astrolabe, the circumference being originally divided into 12 equal parts, corresponding to the signs of the zodiac and months of the year. It had, also, an inner circle, and in each division the principal or prominent stars are found. This instrument is at least 2604 years old, and probably the oldest on record. The ancient astronomers (date unknown) employed copper circles of large diameter placed in the meridian, as also at right angles to that line ; f but we have no evidence how they were divided. Astronomical and other observations were practiced, it is said, in Egypt 3000 B.C. ; as they were also in China 2700 B.C., if Chinese history is worthy of credence. A Chinese emperor, Hwang-ti, is said to have invented the cycle of 60 years, 2600 B.c.J He has also been credited with the invention of various astronomical instruments, including one for observ- ing the four cardinal points, which is generally considered to have been a magnetic compass ; but it was more probably a circumferentor. It is recorded that early Buddhist astronomy possessed instruments made of brass ; but their inferiority and mode of use caused them to give place to larger ones, enormous * Life of the Navigator John Dams (1578), p. 145, 1889. f J. S. Bailly, Histoire de V Astronomic Ancienne, 2d ed., 1781, p. 13. J Davis, History of China, vol. i., p. 219, 1857. \ J. S. Bailly, op. cit., p. 121. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 93 instruments built up of masonry, the divided portion, or arc of the circle, being of marble. With these instruments, angles were measured to single minutes. In 1729 such an instrument existed in Delhi, and a degree upon its divided limb was measured equal to 2-| inches. Claudius Ptolemy, in the second century, possessed similar instruments, as also the astrolabe, with four circles placed in different planes, which had been invented, some 300 years before, by Hipparchus, the greatest discoverer in mathematics, astronomy, geography, etc., of an- cient times. From what has been brought forward, it cannot be fairly argued that the ancients may not have possessed portable cir- cular instruments for rough land-observations long prior to the times of Hipparchus, Ptolemy or Sennacherib. Unfortunately, however, the infamous and ever-to-be-lamented destruction of the Alexandrian libraries, an incalculable loss to the world for all time, has placed it out of our power to determine the par- ticular form, nature and size of the instruments used during the earlier ages. The sculptured and painted figures recently dis- covered upon the walls of a copper-mine at Wady Magerah, which was worked under the reign of the Egyptian King Sene- fura, 4000 B.C., and also the map of an Egyptian gold-mine from 1400 to 1600 B.C., afford strong inferential evidence that mine- surveying was known and practiced at a very early period of the world's history. From that period to the time of Hero and Euclid also improvers of instruments and the science of surveying little of importance is known relative to such mat- ters ; neither have particular details come down to us regard- ing the instruments and mode of surveying adopted during the earlier Greek and Roman mining period. Even the great Roman engineer, Antoninus, does not appear to have employed any angular instrument in determining the direction of the various lines of roads measured by him in the nations con- quered by the Romans. It is highly probable that mine-sur- veying was forgotten more or less, or hid in obscurity for several centuries, as a forbidden art, or suspicious dark practice. Tradition affirms that the first mode of performing surveys in mines in England involved the use of a low, three-legged stool, like a small plane-table, a chalked string, some kind of measure, and a book for entries. It seems that the plane-table 94 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. was fixed at the end of the first bend in the underground road, and the string, held in the direction of the road leading back to the shaft, was then raised a little by the forefinger and thumb, and let fall suddenly, producing upon the table a chalk-line, a portion of which was erased to leave room for succeeding lines. The string was then stretched in a forward direction and treated as before, the measure of the lines being entered in a book, as also the number of the chalk-lines. At the second bend in the road the last preceding forward line was brought into the direction of the last piece of road measured, and the string stretched in a forward direction. Thus a kind of rough traverse-plotting was carried on underground. Undoubtedly, however, that plan of surveying must have been limited to a few lines. It is also probable that such surveys were made with the purpose of repeating them at the surface ; and, if so, the direction of the first line in the underground working must have been determined by suspending two lines down the shafts, which, in those early times, were very shallow. When the writer was a boy he heard an old miner of eighty-four make this statement, and the old man had heard it from his grandfather. Whether this plan of surveying is older than Agricola, 1546 ; Digges, 1571 ; or Houghton, 1681, cannot be determined ; but it is highly probable that it preceded the latter, and continued to be employed after he wrote his work on Sur- veying of Mines. This mode of the three-legged stool may also have given rise to the old-fashioned land-surveying plane- table. It is on record that the " good ship Plenty " sailed from Hull in 1338, directed by the mariner's or sailing (magnetic) needle; so that a rough magnetic compass could have been employed in England for mining and other surveys previous to the time when Agricola wrote ; but there does not seem to be any actual proof that such was the case during the long interval which elapsed until the time of Houghton. Quadrants and plane circular astrolabes, the one divided into 90 and half of the other sometimes to 180, for measuring the elevation of the sun and stars at sea and on land, existed at an early period in the East, in Spain, and in England. The former had plain sights attached to one side, with a plumb-line to mark the angle. The circular instruments had plain sights attached THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 95 to a radial bar, revolving around the circumference in the same manner as in Digges's theodelitus. Such quadrants and astro- labes were sometimes suspended by a ring in the vertical plane of the object to be observed. Two such instruments as those described, of small diameter, are represented upon the second original Borgian Map of the World, by Diego Bibero, Seville, 1529, which map is preserved in good condition in the museum of the Propaganda at Rome. The instruments referred to are divided to single degrees, and, in that respect, are supe- rior to the theodelitus of Digges ; the parts of a degree were esti- mated. An exceedingly curious ancient magnetic compass, with five divided circles, is also engraved upon that map. The instruments of Ribero were of a common type, used long be- fore and after his time, and they present sufficient evidence to prove that these were the models from which the compass of Agricola, 1546, and Digges, 1571, and others were derived. The astrolabe, in fact, in its simplest form was a plane circle (in contradistinction to that with four circles in different planes, sometimes divided half-way round, and sometimes entirely so), and, consequently, must have been used for land-surveying ex- actly in the manner described by Digges. At the International Geographical Congress, London, 1896, the authorities of the British Museum exhibited a number of astrolabes the earliest being one made in Toledo, Spain, in 1067. There were also one made in Valencia in 1086 evidently derived from Moorish or Arabian sources and one made in Cairo, 1240, as well as one made of brass, in England, in 1260, and one formerly belonging to Sir Francis Drake, 1570, besides various others of the fourteenth century and succeeding dates. With the exception of the omission of some types of survey- ing instruments, Mr. Scott has fairly represented in his paper the progress made in various countries in the construction of instruments for the object under discussion. In the copy of Digges's second edition, 1791, in the possession of the writer, Chapter 27, there is a diagram of his 2-foot surveying circle theodelitus a copy of which was sent to Mr. Scott. We cannot suppose, however, that a circle of so large a diameter was commonly used in mines; still, it could have been so em- ployed. Nothing would be gained by following Mr. Scott in detail, because he has done his work so well. 96 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. It would appear, however, that little improvement was made in land- and underground-surveying instruments up to the time when Ramsden. completed, about 1760, the grand inven- tion which he applied in practice during the period from 1784 to 1799. Others followed, some time prior to 1788, in Ger- many, and also probably in France about 1790. As far back as 1804, Fenwick, a celebrated surveyor and colliery viewer of Durham, England, proposed the plan of a " fast needle," as he termed the circumferentor or rough theodolite-limb, constructed in his time. Still, he had to depend upon the magnetic needle to obtain the bearing of some selected line in the survey. Fenwick's book contains a complete system of magnetic-com- pass or dial surveying, and, so far as that system is concerned, it has not been, nor will it ever be, superseded. Various opinions had been emitted from Fenwick's time up to 1842, when Butler Williams,* a prominent English civil en- gineer, suggested the necessity of improving the theodolite and adapting it more generally to mine-surveys. He also wrote a very concise and exceedingly useful chapter upon underground surveying, suggesting the use of three tripods, as also a system of plotting underground surveys by co-ordinates. Combes and D'Aubuisson had formerly attempted to introduce some such plan ; still, such was the opposition and obtuseness of that period, that the miners' dial in some form or another was, and still is, continued in use for mine-surveying. Various authori- ties have stated that the writer was the first in England to publish, in 1863, a general system of mine-surveying by the sole use of the theodolite. That work advocated plotting un- derground surveys by the co-ordinate system, and for this and other useful purposes a complete set of traverse-tables formed part of the work alluded to.f Although no account of the miners' transit-theodolite (Fig. 74) was published earlier than 1863, still the writer believes that he had it in use prior to 1858. By means of a long diagonal eye-piece, the instrument was intended to be used for con- necting underground workings to the surface by direct sight- ing up a shaft, and fixing an illuminated wire in the same direc- * Practical Geodesy, B. Williams, C. E., pp. 207, 219, 1842. t Practical Treatise on Mining, Land and Railway Surveying and Engineering, Lon- don, 1863. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 97 FIG. 7.4. HOSKOLD'S MINERS- TRANSIT THEODOLITE/^ In tl.e right-lard lower corner is shown the method of mounting upon three leveling-screws. 98 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. tion as the first drift underground. In deep and wet shafts this plan was impracticable ; but in shallow dry pits, when the operation was performed on dark nights, fair success was ob- tained. For deep pits, the writer found that two chains made in a particular form of steel wire of different sizes, to support the weight suspended down a shaft for determining the direc- tion of the first line in the underground survey, were com- pletely satisfactory. The theodolite, Fig. 75, was designed soon after that repre- sented by Fig. 74 ; but it was not constructed until about 1862- 63, and an account of it w T as published in 1865.* However, some defects had been introduced in the construction, and being pressed for time, the writer did not attend further to the matter until 1889, when Troughton & Simms made some alter- ation in the instrument, making it as represented in Plates I. and II. of the writer's paper, published in 1893.f That firm also constructed a new instrument of the same class as that under consideration, introducing some improvements repre- sented in Fig. 75, which was exhibited in the Argentine Mining and Metallurgical Section at the Chicago Exhibition in 1893. The jury on scientific instruments gave the highest award for the instrument, finding the chief points of excellence in it to be as follows : " 1. It is an instrument of new appliances. "2. Peculiarity, beauty and novelty of construction. "3. Adapted to facilitate surveying operations with greater accuracy and in less time than is usual with surveying instruments. "4. It is a general labor and time saver." As may be seen in Fig. 75, one of the principal improvements consists in the adaptation of a second, or, as we should term it, lower telescope, arranged to move upon a short horizontal axis, the telescope occupying an elongated or oval-shaped opening made in the center of the enlarged part of the lower vertical axis. Each end of the short horizontal axis is suspended in a collar between four adjusting screws, which pass through the termination of a short horizontal cylinder, the collar of which is firmly screwed or cast to the outside of the lower vertical * Trans. S. Wales Mining Engineers, vol. iv., No. 5, 1865. f Trans. Am. Soc. Civ. E., vol. xxx., pp. 135-154, 1893. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 99 FIG. 75- HOSKOLD-S ENGINEERS' THEODOLITE > 100 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. axis. The telescope is thus secured against lateral vibration, and, by the two sets of screws named, may be adjusted to coin- cide with the optical axis of the upper telescope when the zero of the verniers coincides with 360, 90 and 180. It moves vertically a few degrees, sufficient for sighting elevated or de- pressed objects within its range, upon the surface. For use underground, when elevated or depressed stations are beyond the vertical range of the telescope, a reflector applied to the object-end of the lower telescope reflects any object situated in the perpendicular or vertical ; or the upper telescope may be used instead. By an ingenious contrivance of the maker, this reflector may be attached or detached at pleasure, and, when attached, its lateral plane or reflecting-surface is at right- angles to the optical axis of the telescope. The upper telescope is mounted on Y's sufficiently high to give the amount of vertical angle which may be required in any class of mine ; and its horizontal axis carries a divided semicircle on each side of the telescope, giving a perfect bal- ance to the upper parts of the theodolite, without employing useless dead counterpoise weights. A groove about three-quar- ters of an inch in width and four inches in length is fixed upon the upper telescope, into which a corresponding part of a large circular, as also a long-trough, magnetic compass may be slid for use underground or upon the surface, independently of, or in connection with, the readings of the theodolite-limb. The circular compass carries a long sensitive needle with a vernier at each end, which may be made to read either to single minutes or to 20 seconds, as may be required. The horizontal axis of the upper telescope is perforated to admit the rays of light from a lantern to illuminate the hairs underground ; or, for night-work, a reflector is also attached to the lower telescope. A sensitive stride, or axis-level is provided also. A special form of micrometrical eye-piece, not shown in Fig. 75, is attached to the telescope when required, and may be made to read to single seconds. Its chief use is the determination of distances by the sub-tense system,* which, in the opinion of the writer, is much superior to the stadia plan. This micrometrical apparatus may also be used as an auxiliary to the readings obtainable from the verniers of the theodolite. * Trans. Am. Soc. Civ. E., vol. xxx., pp. 147, 148. THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 101 The simple but efficient arrangement of two telescopes in the instrument under notice enables an observer to dispense with the usual practice of making the zero of the verniers coincide with 360 , 180, etc., or zero of the divided circle, every time any angle has to be measured in traverse or circuitous survey- ing, thus reducing the time and labor at least to one-half of that required by the use of other classes of surveying-instru- ments, and, at the same time, securing greater accuracy and certainty in the final results. The modus operandi is simply to set the instrument over a station, properly level it, and direct the lower telescope upon the back-station, and the upper telescope upon the fore-station, neglecting the vernier readings during the operation ; then a single reading determines the amount of the observed angle between the optical axes of the two telescopes, which is also that between the two stations. If the observer has not sufficient confidence in his manipulation, or suspects that some slight displacement of the instrument or slipping of the screws has occurred during the interval of the observation, he may decide the question instantaneously by applying the eye to each tele- scope in quick succession, when, if no error has been intro- duced, the vertical hairs of each telescope will continue to strike through each station-mark. If, on the contrary, any slipping of the parts of the instrument has resulted, it is instantly cor- rected by applying the eye first to the lower telescope, bisecting with the body tangent-screw, and then to the upper one, per- forming the same operation with the upper tangent-screw. Or, if the error was only due to an imperfect observation made with the upper telescope, the last operation will suffice for the correction. However, with proper care, no such vitiating error should occur. It is apparent that with the use of a theodolite having only one telescope, no such instantaneous check-proof can be obtained at each station, at least without reversing the telescope from the fore- to the back-station, or vice versa, and then examining the vernier-zero in order to determine if it coincides with the zero of the divided circle as at first fixed. Each of the known modes of measuring horizontal angles in traverse or circuitous surveying requires two separate readings before an angle can be determined. This would be the case when the vernier-zero 102 THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. is made to coincide with 360 at only the first angle, and when at each succeeding station each preceding angle or fore-reading is made to become the back-reading alternately. For the engi- neer is never certain that some slight displacement has not occurred during the transit from one station to another, due to jarring or the slipping of screws, verniers and divided circle, contraction or expansion of parts ; or it may be that the opera- tor has unconsciously touched the tangent-screw of the vernier and divided circle, etc., rendering a constant examination of the vernier-readings an absolute necessity for both back- and fore-readings, comparing them with the book-entries, all of which means a waste of time and extra mental and manual labor. To insure absolute freedom from error, when the ver- nier-zero is employed for all the back-observations, it is neces- sary to observe the supplementary angle, or, at least, repeat the angle, either of which would involve four separate operations and readings. On the contrary, even when the supplementary angle is taken by the theodolite under consideration, Fig. 75, only two separate readings are required. For example, suppose that the angle is 178 35' 15", and the supplementary equals 181 24' 45", then 178 35' 15" + 181 24' 45" = 360, as it ought to be, if the instrument is in perfect adjustment and the manipu- lation is correct. Any difference from an entire circle would show the amount of error plus or minus. A small . amount of error, amounting to from 15" to 20", will sometimes exist, when instruments are inferior, and is difficult to eliminate. It will, therefore, be manifest that the lower telescope is capable of rendering incalculable service. This instrument may also be made to take the place of a transit-theodolite for a variety of operations, especially in pro- ducing transit lines. For example, when it is necessary to pro- duce any given line a frequent operation in a certain class of surveys it is done by first placing the telescopes to look in opposite directions, making the zeros of the* three verniers of the horizontal circle coincide nicely. The lower telescope is then directed to the back-station ; and the optical axis or ver- tical wire in the upper telescope points out the direction of the transit line. The verniers being double, there are nine distinct readings by which to effect the coincidence before producing the THE EVOLUTION OF MINE-SURVEYING INSTRUMENTS. 103 line ; and as the verniers read to fifteen seconds, the probable error, plus or minus, would be ^- 1.66 seconds. It is doubtful whether a line could be prolonged by a transit-theodolite within this limit of error. "Where townships or extensive areas of land are required to be set out in blocks, this instrument would prove invaluable, for the reason that the two telescopes may be set at right- angles at the commencement of a day's work, and the corre- sponding work set out with the greatest facility and accuracy. It may, however, be convenient to examine the vernier-readings as the work proceeds. In the wide arms carrying the reading-microscopes, and just behind each of them, a hole is drilled, and on the top of each hole a reflecting prism is screwed, having a horizontal motion, so that each of them may be turned until a ray of light is caught and reflected upon the verniers, which are thus effectu- ally illuminated, so that it is not necessary to bring the light of a candle or lamp inconveniently near the head when the angles are read. When the instrument is used on the surface, the long or trough magnetic compass is slipped into a corresponding groove to receive it under the horizontal divided circle, or on the top of the upper telescope. By preference, a triangular leveling- and centering-frame of light weight, with three leveling-screws, is attached to the theodolite, Fig. 75. The conical heads of these screws are locked by a slipping plate into a similar triangular frame, which is screwed to the top of the tripod-stand. This leveling- frame carries two other thin movable plates, and vertical pins working in elongated slot-holes, and a circular clamping-ring. By means of this beautiful apparatus, invented by Troughton