W.&L.E. GURLEY Ol UNIVERSITY OF CALIFORNIA DEPARTMENT OF CIVIL. ENGINEERING BERKELEY. CALIFORNIA A MANUAL OF THE PRINCIPAL INSTRUMENTS USED IN AMERICAN ENGINEERING AND SURVEYING MANUFACTURED BY W. & L. E. GURLEY TROY, N. Y., U. S. A. FORTY-EIGHTH EDITION PRICE ONE DOLLAR PUBLISHED BY W. & L. E. GURLEY TROY, N. Y. 1921 I?*-/ Library ^Library Entered, according to Act of Congress, in the Year 1911 By W. & L. E. GURLEY In the Office of the Librarian of Congress, at Washington COPYRIGHT, 1912 By W. & L. E. GURLEY COPYRIGHT, 1914 By W. & L. E. GURLEY COPYRIGHT, 1921 By W. & L. E. GURLEY OFFICE &\VORI \V&L.E.GURLEY Engineering Library GrURLEY'S MANUAL is primarily a book of instructions in the adjustment and use of field instruments. Simplicity of ex- pression is sought and no attempt is made at treatises which are more properly to be found in technical publica- tions. 800336 PREFACE IN presenting this edition of our Manual we offer the engineering profession many new field instruments, new features and refinements, resulting from con- tinuous effort and study for a period of seventy-five years. The House of W. & L. E. Gurley is the largest as well as the oldest American manufacturer of engineering instruments and our line is the most desir- able and also the most complete of its kind in the world. The merit of any article is fully determined by its ability to stand the test of time, and the service given by GURLEY INSTRUMENTS for three-quarters of a century proves that they possess those characteristics which qualify them for the most exacting demands of modern engineering practice. In our zeal for offering only the best we have looked beyond the vision of commercialism and our entire organization takes great pride in our finished products as they leave our hands to fulfill their mission of locat- ing, developing and conserving the resources of nature and the upbuilding of those projects which tend to the welfare and comfort of mankind. W. & L. E. GURLEY. LIST OF ILLUSTRATIONS FIG. ILLUSTRATION PAGE 1. Cross Section of Transit 24 2. No. 154 showing Dust Guard for Objective. . 26 3. Platinum Cross Wires 28 4. One Piece Truss Standard 30 5. Radially Ribbed and Dished Limb and Plate and Tapered Centers 32 6. Top Plate of the Light Mountain Transit, showing location of verniers, levels, varia- tion arc pinion, and needle lifter screw. ... 33 7. Limb 1 36 8. Limb IV 37 9. No. 149 Beaman Stadia Arc 40 10. No. 27-A Precise Transit 44 11. No. 10- A Precise Transit 4^ 12. View of Hell Gate Bridge during construction 48 13. No. 18-A Precise Transit, Hell Gate Model. . 49 14. No. 10-A-3 Precise Transit with three screw leveling head 53 15. No. 28 Light Mountain Transit 55 16. No. 20-A Explorers Precise Transit 57 17. Explorers Transit with its special jointed Extension tripod, canvas carrying case, and leather covered wooden box 58 Explorers Transit, with its special tripod, packed in a dress suit case 24 in. long. ... 59 19. No. 102 Reconnoissance Transit 61 20. Stadia Constant (Diagram) 71 16 W. & L. E. GURLEY, TROY, NEW YORK FIG. ILLUSTRATION PAGE 21. Diagram (To adjust line of collimation) . ... 78 22. No. 136 Vertical Circle with No. 141 Alum- inum Guard 85 23. No. 138 Vertical Circle with two opposite double verniers, and guard 86 24-. No. 139 Vertical Circle, 4.5 in. diameter with graduations on edge or rim, protected by a metal guard. Circle, etc 87 25. No. 139-A, 139-B and 140 Vertical Arcs. ... 88 26. No. 145 Level on Telescope 89 27. Graduations of Beaman Stadia Arc 92 28. No. 150 Gradienter 96 29. No. 160-161 Detachable Side and Riding Telescopes for vertical sighting in mine surveying 101 30. No. 165-166 Cross Wire Illuminating Re- flectors 103 31. No. 168 Diagonal Prism 103 32. No. 170 Plummet Lamp 104 33. No. 180 Attached Magnifiers 106 34. No. 192 Solar Screen 106 35. No. 190 Burt Solar Attachment 115 36. No. 30-A Precise Transit with Burt Solar Attachment 119 37. No. 196 Striding or Adjusting Level 123 38. No. 32-A Precise Transit 138 39. No. 226 Vernier Compass 150 40. No. 241 Leveling Adopter . 158 41. No. 242 Leveling Head 159 LIST OF ILLUSTRATIONS 17 FIG. ILLUSTRATION PAGE 42. No. 262 Telescopic Sight 160 43. Compass fitted with No. 262 Telescopic Sight, etc 162 44. No. 294 Compass 167 45. No. 285 Compass 168 46. No. 335 Geologists Compass 171 47. No. 341-A Dip Compass 174 48. No. 350 Dial Compass 176 49. No. 3154 Wood Box Pocket Compass 180 50. No. 375-377 Engineers Wye Levels 182 51. Sectional View of Engineers Wye Level. ... 183 52. No. 378 Engineers Wye Level 1 84 53. View of Engineers Wye Level, etc 185 54. No. 381 Architects Level 189 55. No. 384 Explorers Level 197 56. No. 643 Locke Hand Level 202 57. No. 646 Abney Hand Level 203 58. No. 640 Monocular Hand Level 204 59. No. 500 Philadelphia Rod with Micrometer Target 210 60. No. 500-R Philadelphia Service Rod with Oval Target 211 61. No. 500-B Philadelphia Rod 212 62. No. 501 Philadelphia Rod 213 63. No. 501-B Self-Reading Rod 214 64. No. 505 New York Rod 215 65. No. 510 and 511 Architects Rods . . 216 18 W. & L. E. GURLEY, TROY, NEW YORK FIG. ILLUSTRATION PAGE 66. No. 517 Slip Jointed Rod 217 67. Front and Rear View of No. 517 Slip Jointed Rod, showing joints 217 68. No. 514-B and 514-C Stadia Rod 218 69. No. 514-D and 514-E Stadia Rod 218 70. View of Hinges, ribbed brace and clamp of Telemeter or Stadia Rod 219 71. No. 513 Telemeter or Stadia Rod . . . ^ ,*^_. 220 72. No. 516 Cross Section Rod 221 73. View of Hinged Joint 222 74. No. 524-A Plain Leveling Rod without Target 223 75. View of Clamp of Plain Two Ply Leveling Rods 223 76. Rear View of Lower Portion of Four Ply Rod No. 524-A 223 77. No. 522-A Plain Two Ply Leveling Rod. 224 78. No. 551-R Molitor Precise Rod, Front View. . 224 79. No. 551-R Molitor Precise Rod, Rear View. . . 224 80. No. 552-R Self Reading Tape Leveling Rod, front 225 81. No. 552-R Self Reading Tape Leveling Rod, side 225 82. Precise Leveling Rod 227 83. Nos. 525-B to 528 Flexible or Pocket Level- ing Rods 229 84. No.530, 531 Combined Leveling Pole and Flagstaff 230 85. No. 534 to 536 Wooden Flagstaff 230 LIST OF ILLUSTRATIONS 19 FIG. ILLUSTRATION PAGE 86. Nos. 540-A to 544 Iron and Steel Ranging Poles 231 87. Nos. 537-A to 538-B Flagstaffs 232 88. No. 545 Rod Level as applied to a Rod 233 89. No. 546 Rod Level 234 90. No. 547 Rod Level 235 91. No. 548 Rod Level 236 92. Nos. 415, 416, 400 and 430 Solid Round Leg Tripods 238 93. Nos. 405, 435, 410, 440 Split and Extension Leg Tripods 239 94. Nos. 412 and 443 Jointed Extension Leg Tri- pods for Explorers Transits and Levels. . . 241 95. No. 576-C Plane Table Outfit, etc 244 96. No. 570 Johnson Plane Table Outfit 245 97. No. 584-C Telescopic Alidade, etc 246 98. No. 592-C Explorers Alidade, etc 249 99. No. 586 Traverse Plane Table Outfit 257 100. Traverse Plane Table Movement, etc 250 101. No. 590-A Pocket Sight Alidade 259 102. No. 594 Army Sketching Case 261 103. Showing Method of using Fiala Scout Sketching Case 264 104. No. 596 Fiala Scout Sketching Case 266 105. Nos. 450 to 458 Plain Plummets 272 106. Adjustable Plummet showing Details of Con- cealed Reel, No. 465 273 107. No. 616 Acoustic Current Meter Outfit 277 108. No. 623 Electric Current Meter Outfit, etc. . 279 20 W. & L. E. GURLEY, TROY, NEW YORK FIG. ILLUSTRATION PAGE 109. No. 623 Electric Current Meter Outfit, etc. . 280 110. No. 609 Electric Register 281 111. No. 628 Hook Gage 283 112. Section of Paper Tape, showing printed record, made, etc 289 113. No. 630 Printing Water Stage Register, etc. 290 114. No. 633 Graphic Water Stage Register, etc. 293 115. No. 637 Long Distance Graphic Water Stage Register, showing the Receiver attach- ment 296 116. No. 638 Float Operated Sender, for Long Distance Graphic Register 299 117. No. 639 Long Distance Indicator with 12 in. Dial 300 118. No. 639-A Indicating Gage 301 119. No. 9570 Precision Balance 303 120. Packing Box 309 Gurley Precise Mountain Transit TRANSITS CONSTRUCTION OF TRANSITS THE TRANSIT is by far the most important and indispensable instrument of an engineers' outfit. With it the engineer can read and lay off both horizontal and vertical angles, determine a level line or the difference in elevation between two points, read dis- tances by means of the stadia, measure grades and distances with the gradienter and determine the meridian by the compass, by direct observation, or by the solar attachment. The distinguishing features of Gurley Transits as developed after many years of study and experience, are their simplicity of construction, ease of manipula- tion, and accuracy and permanence of adjustments, which are all made without undue strain on any part. The essential parts, which may be seen in the illus- trations, and in section in Figure 1, are the telescope with its axis, the standards, the circular plates with their attachments, the sockets upon which the plates revolve, the leveling head, and the tripod upon which the whole instrument stands. TELESCOPE. The different parts of the telescope are shown in Fig. 1. An achromatic lens (H) at the enlarged end of a sliding cylinder mounted near each end, in bearings (I) of hard babbitt metal, is moved out or in to bring the focus of the rays of light from the object viewed to an inverted image in the plane of the cross wires (J) to be there magnified by an eyepiece (T-W), and restored to its natural position. FIG. 1 CROSS SECTION OF TRANSIT TRANSIT INSTRUMENTS 25 The telescope is secured to an axis having multi- grooved bearings (F) fitted in the standards, allowing the telescope to transit at both ends. The various sizes of telescopes, made to suit the instruments on which they are to be used, are of the best quality. They must be free from chromatic and spherical aberration and of as high a magnifying power as is consistent with good illumination and sharp defini- tion, or resolving power. The lenses, however good, must be so accurately mounted that the optical axes of all of them will be in one straight line. This imaginary line, called the line of collimation must be at right angles to the axis of revolution for all positions of the focusing slide. OPTICAL Axils. The intersection of the cross wires forms a point which, when adjusted, enables the observer to fix the telescope upon an object with pre- cision. The process of bringing the intersection of the wires into the optical axis is called the adjustment of the line of collimation. One of the babbitt bearings (I, Fig. 1) of the objec- tive slide is supported in a ring and can be adjusted with the screws (C C). The adjustment of the objective slide, which is described on pages 74 and 75, keeps the line of collima- tion in adjustment through the whole range of the slide without placing any strain on the slide or bearings. This adjustment, which is one of the distinctive features of Gurley telescopes, permits the alignment of both wires with equal accuracy, which is impossible without 26 W. & L. E. GURLEY, TROY, NEW YORK it. The slide adjustment is always made in the process of manufacture, and needs no attention from the engin- eer, unless the instrument is severely injured. The slides are now made to focus at any distance from four and one-half feet to infinity. FIG. 2 No. 154 SHOWING DUST GUARD FOR OBJECTIVE DUST GUARD (No. 154) for the objective slide, is placed on all our Transit Telescopes. A velvet band effectually prevents any particle of dust or foreign substance from interfering with the perfect action of the slide. It also helps protect the objective slide from injury. CENTER POINT. To facilitate the setting of the transit precisely under a given point, we make in the top of the ball of the telescope axis and directly over the center of the instrument, a small conical hole or center point. EYEPIECE. Four lenses, (T, U, R, W,) form a compound microscope that focuses on the image at the cross wires and conveys the magnified image to the eye, in an erect or natural position. Sometimes an eyepiece TRANSIT INSTRUMENTS 27 of but two lenses is used. While this absorbs less light and therefore gives a more distinct image, it presents to the eye an inverted image of the object viewed. American engineers usually prefer the erect image. The centering of the eyepiece is effected after the wires have been adjusted, by moving the ring and babbitt bearing with the screws, AA, shown on the outside of the tube, until the intersection of the wires is brought into the center of the field of view. MAGNIFYING POWER. The apparent size of an object viewed through the telescope is as many times greater than the image which the naked eye sees, as the number which expresses its magnifying power. A tele- scope which magnifies twenty times, increases the visual angle in this same proportion, and therefore diminishes the apparent distance of the object to one- twentieth of the actual distance. In other words, it will show an object two hundred feet distant, the same size as if it were only ten feet from the naked eye. It is often supposed that the greater the power of a telescope the better it is; but beyond a certain limit, this is not true. As only a given amount of light can enter the objective, the more the object is magnified the less clear and bright will it appear. A power of from sixteen to twenty-six diameters in the telescopes of transits gives the best results for regular use. 28 W. & L. E. GURLEY, TROY, NEW YORK PLATINUM CROSS WIRES. The cross wires in Gurley tele- scopes are filaments of platinum, mounted on the face of a heavy brass ring which will always retain its shape. They are placed at right angles with each other, so as to divide the field of view into quadrants, and are adjusted in the line of collimation by means of the four capstan head screws, BB and B'B', Figure 3. For special cases they can be mounted in many other forms. The advantages of platinum over spider web have long been conceded. It is smooth, opaque and unaffected by moisture. The desirability of non-transparent wire is manifested when sighting against the sun or when observing a lamp as in mine w T ork. We are successfully drawing wire to one fifty-thousandth of an inch in dia- meter. For transits we use wire one ten-thousandth of an inch in diameter, selected according to the degree it is to be magnified. Unless otherwise specified we supply fixed stadia wires with most of our instruments as they are preferred by the majority of engineers because they cannot be thrown out of adjustment accidentally. TRANSIT INSTRUMENTS 29 However, when requested, we will substitute adjust- able stadia wires which are necessary if the user wishes to change his unit of measurement from feet to chains (1 : 100 -1 : 66). In all cases where the ratio is 1 : 100 the interval between the stadia wires need not be changed as the ratio 1 :100 is good for one foot to one hundred feet, one meter to one hundred meters or one vara to one hundred varas. DISAPPEARING STADIA WIRES. The Stadia Wires are usually arranged in the same focal plane with the cross wires so that they may be seen at the same time. When desired, however, they may be placed so that they are out of focus when the cross wires are visible; and conversely when the stadia wires are in focus, the cross wires are invisible. Some engineers like this method, but it has the disadvantage that changing the focus from stadia wires to cross wires or vice versa, necessi^ tates a change of the objective focus. For this reason, the majority of engineers prefer the regular system; that is, with all the wires in one focal plane. This arrangement of the wires also enables them to observe, by means of the vertical cross wire, whether the rod is being held plumb. BEAMAN STADIA ARC. The Beaman Stadia Arc, described on page 90, which is made exclusively by W. & L. E. Gurley, avoids the use of all stadia compu- tations in inclined sights. It can be attached to any Gurley transit or telescopic alidade having a vertical limb four inches in diameter or larger. 30 W. & L. E. GURLEY, TROY, NEW YORK THE STANDARDS. The axis on which the telescope revolves, or transits, is supported in a most substantial manner. The original design of the standards has been much improved by adopting an angular section and enlarging the bases so that two strong screws in each base may firmly secure them to the ribbed plate. Such standards are supplied with our Light Mountain and Reconnoissance Transits. FIG. 4 ONE PIECE TRUSS STANDARD PATENTED JULY 25, 1916 A new design (patented), as here shown, was recently introduced by us and represents the greatest advance in instrument construction. It is stronger and TRANSIT INSTRUMENTS 31 more rigid than any other form of standard. Cast of the toughest bronze, in one piece, and with angle cross section, it provides the greatest rigidity with the least possible weight. The principle of diagonal cross brac- ing is used here and the supporting members are carried as far up on the legs as is possible without interfering with the use of the instrument. The base is wide, and its attachment to the top plate by eight large screws allow r s the development of the full strength of the deeply ribbed plate for support and reinforcement, making the whole structure mechanically one piece for withstand- ing stress. The finish of the standard is a beautiful and very durable morocco, applied directly to the surface of the casting, which thus retains its skin intact. The internal stresses of the metal are relieved by a process of artificial aging in which the metal assumes its perma- nent set without any loss of its tenacity or rigidity. The bearings for the axis are of perfect circles in cross- section, but instead of being plain cylinders, they have V threads of zero lead. They are always ground into place to insure a perfect fit. This form of ground multi-shoulders, as illustrated at F, Fig. 1, adds rigidity to the standards and automatically prevents any loose- ness or lateral motion, regardless of any possible wear through long use. On the right hand bearing of the standard there is an adjustable block whereby the axis may be made truly horizontal or at right angles to the vertical spindle. THE Axis CLAMP AND TANGENT, which is regularly supplied on all transits, consists of an arm, K, Fig. 1, 32 W. & L. E. GURLEY, TROY, NEW YORK one end of which encircles the telescope axis, and can be clamped to it. The other end is held between the tangent screw on one side and the tangent slide and spring on the other. These are supported from the standards. When clamped the telescope may be tilted slowly by means of the tangent screw ; when undamped, it may be revolved freely in either direction. FIG. 5 RADIALLY RIBBED AND DISHED LIMB AND PLATE, AND TAPERED CENTERS THE MAIN PLATE. By a system of deep ribbing, the top plate has been materially stiffened without add- ing to its weight, and the liability of warping with age has been reduced. It carries the standards supporting the telescope, the compass box with its movement for magnetic declination, the verniers for the horizontal limb, two levels at right angles to each other, and the support for the tangent screw for movement about the vertical axis. Note Fig. 10 that the longitudinal plate TRANSIT INSTRUMENTS 33 level is of extra length, providing a more precise check when measuring vertical angles than is possible with a short level. FIG. 6 TOP PLATE OF THE LIGHT MOUNTAIN TRANSIT, SHOWING LOCATION OF VERNIERS, LEVELS, VARIATION ARC PINION, AND NEEDLE LIFTER SCREW THE COMPASS CIRCLE is silvered, graduated and figured to 90 each way. The graduations of this circle, on Transits Nos. 6-A to 18-A, are half degrees and the declination arc reads bv vernier to one minute. 34 W. & L. E. GURLEY, TROY, NEW YORK On Transits Nos. 25-A to 32-A the compass circle is graduated to whole degrees and the declination arc reads by vernier to five minutes. The declination arcs are movable by a pinion. THE COMPASS Box containing the needle is covered by a glass to exclude moisture and air. These covers on all Gurley transits are made of specially selected plate glass, beveled on the edge and set flush with the bezel ring, thus facilitating the removal of moisture from the top of the glass and affording an unobstructed observa- tion of the compass face. THE MAGNETIC NEEDLE, made of special magnet steel, has a cap in which is inserted a polished jewel center and this, resting upon the hardened and polished point of the center pin, allows the needle to play freely and settle in the magnetic meridian. The needle has on its South end (North end for Southern hemisphere) a coil of wire, easily moved to adjust the balance of the needle against dipping. The needles are balanced as nearly as possible for the loca- tion to which they are to be shipped, so that only a slight adjustment should be necessary. A screw passing through the upper plate moves a concealed lever by which the needle button is raised against the setting, thus lifting the needle from the pin so as to check its vibration, or to hold it up against the glass when not in use, avoiding unnecessary wear of the jewel center and the pivot. The test of the delicacy of a magnetic needle is the number of horizontal vibrations which it will make in a TRANSIT INSTRUMENTS 35 certain arc before coming to rest. Most surveyors desire also a quivering motion in the needle. This quality, which is manifested more in a horizontal than in a vertical needle, depends upon the close coincidence of the point of suspension with the center of gravity of the needle, and merely serves to show that the cap is unobstructed. PLATE LEVELS. The two plate levels, mounted on brass posts or studs, are at right angles to each other so as to level the plate in all directions. The position of the levels, near the edge of the plate, makes them accessible for adjustment and permits the use of longer and consequently more accurate levels than if placed inside the compass box. These levels are held firmly in place by the capstan nuts above and below each end. They cannot possibly be jarred out of position. Their adjustment is made by turning the capstan head nuts at either end. The glass vials used in the levels of all Gurley transits are ground on their inner surface to give the bubble an even motion and the required degree of sensitiveness. HORIZONTAL LIMB. All cast metal parts, but more particularly the casting of the limbs, should be thoroughly aged. A fresh casting will shrink and warp like a piece of wood, but, of course, to a lesser degree. We machine the limbs, apply the sterling silver, and then completely season them before putting them through the final operations of finishing and graduating. To secure the utmost accuracy and to avoid any possi- bility of molecular changes, the limbs are finished and the figures engraved before the graduating is done, 36 W. & L. E. GURLEY, TROY, NEW YORK which is the last process before they are placed in their respective instruments. The form of the limb has been considerably changed by a greater dishing, which adds to the rigidity and allows deeper ribbing. 88 I . til & L. E. Gurley Troy, N. Y. Limb I. The figures are in two rows, in quadrants from to 90 each way inner row, and from to 360 outer row. FIG. 7 The graduations, cut on sterling silver, are usually to half degrees, reading by vernier to one minute. If desired, they may be cut to thirds, quarters or sixths of TRANSIT INSTRUMENTS 37 a degree, with verniers reading to thirty, twenty, fifteen or ten seconds, but at an additional cost. This is known as the sexagesimal system. If desired, one or both verniers may be graduated to read to one-hundredth or one-fiftieth of a degree. W. & L. E. Gurley Troy, N. Y. The figures arein two rows, each row from to 360, but reading in opposite directions, and inclined in the direction in which they increase. FlG. 8 Another form is to graduate the limb to one hundred grads to the quadrant, the vernier reading to one one- hundredth of a grad. This is called the centesimal svstem. 38 W. & L. E. GURLEY, TROY, NEW YORK In artillery practice, the mil is used because of its convenience in the rapid calculation of small angles in fire control. For this purpose the mil is taken to be 1/6400 of a circumference. LIMB FIGURING. Various methods of figuring are employed. The two forms most commonly used are shown on pages 36 and 37. Limb I has two rows, the inner row figured in quadrants as a compass circle and the outer row from continuous to 360, reading clock- wise. Limb IV has two rows of figures, each to 360, but in opposite directions and inclined in the direction of increase. THE VERNIERS. As shown at V in the sectional cut, Fig. 1, the horizontal verniers are attached to the main plates and revolve within the horizontal limb, with their surfaces flush and so close that there is no apparent parallax. They are placed thirty degrees to the left of the line of sight and can be easily read without change of position by the observer. They are covered with selected plate glass carefully cemented to exclude moisture and dust. The upper surface of the glass is flush with the plate, thus they are easy to clean and there are no frames or rims to cast shadows or col- lect dust. The use of two opposite verniers give the means of cross checking the graduations and the perfection with which they are centered. Thus the accuracy of the angle readings is indicated. ONE GRADUATION is ADDED to each end of the vernier to enable the last numbered division to be more easily TRANSIT INSTRUMENTS 39 read but this has only the practical use indicated and is not considered in calculating the smallest reading of the vernier. With the exception of the extra graduation mentioned above, the number of spaces on the vernier at one side of the zero graduation is equal to the number of parts into which the smallest division on the limb is to be divided. To FIND THE SMALLEST READING OF THE VERNIER, divide the value of the smallest space on the limb by the number of parts into which this space is to be divided, the resulting quotient is the smallest reading of the vernier. Thus in Fig. 9 we have a vertical limb graduated into half degrees or thirty minute spaces, the vernier is shown between the standard legs and is divided into thirty parts either side of the zero; the vernier therefore reads to one thirtieth of a graduation or a single minute. To READ THE TRANSIT VERNIER. Note the position of the zero on the limb and read to the nearest whole space the position of the zero of the vernier with respect to it. Reading in the direction of increasing limb figures, count the graduations on the vernier from zero to the one which coincides with a graduation on the limb. The sum of these two readings will be the read- ing required. Divisions should be counted in the direction of in- creasing limb figures. For example, in Fig. 9, the vernier zero reads be- tween 5 and 5%*. Counting the vernier divisions to the left, it is seen that the 16th line coincides with a line of the arc. The correct reading is therefore 5 16', 40 W. & L. E. GURLEY, TROY, NEW YORK Had the vernier zero read between 5% and 6, the vernier reading would have been added to 5 1/2 and the result would have been 5 46'. REFLECTORS. Reflectors of white opaque celluloid, or of glass if preferred, are placed back of the horizontal verniers to reflect a white light and to eliminate glare. FIG. 9 No. 149 BEAMAN STADIA ARC, ATTACHED TO THE VERTICAL ARC OF A TRANSIT TRANSIT INSTRUMENTS 4-1 THE LIMB CLAMP AND TANGENT. The tangent hanger, fastened to the edge of the main plate, carries the tangent screw and nut on one side, and opposed to them the tangent spring, slide, and barrel. The spring is made large enough to give practically the same force throughout the length of its travel. The limb clamp, D, Fig, 1, is a heavy ring and arm which is fitted on the socket so as to turn freely. The clamp screw, E, pushing against a plunger, operates to clamp the ring firmly around the socket without tend- ing to turn it. The arm of the clamp is held between the tangent screw and spring. When the clamp screw, E, is loosened, the plate may be freely turned to any desired position for setting the verniers or sighting the telescope. When the clamp screw is turned lightly against the plunger, the plate is held firmly in position with reference to the limb ; and it may be given a very slow motion by turning the tan- gent screw. Because of the special form of Gurley clamps, only a very light pressure of the clamp screw is necessary to make them hold. The heads of the clamp screws are therefore made small to prevent unnecessary force being applied to the screw and clamp. THE SOCKETS. The sockets are compound. The interior spindle Y, Fig. 1, attached to the main plate carrying it and its attachments turns in the inter- mediate socket S to which the limb is attached. When clamped, this socket turns in the socket of the leveling head, governed by a second clamp and tangent movement with opposing spring. 42 W. & L. E. GURLEY, TROY, NEW YORK The sockets or centers are constructed with the greatest care, are of carefully chosen composition and are made of different degrees of hardness to eliminate friction and wear. They are truly concentric, are of substantial diameter and length and are designed to pro- vide maximum stability in the most vital parts of the instrument. THE LEVELING HEAD. The outer socket has four ribbed arms that bear the nuts for the leveling screws. At its lower end there is a hemispherical nut fitting in a corresponding cup in the shifting center, which is the center of movement when leveling. The leveling screws are nicely fitted with long bearings in the nuts and are protected from dust by covers. The lower ends of the screws rest in cup bearings fitted with fiber bushings to eliminate friction. The cups avoid marring the plate when shifting the instrument from side to side on the tripod. To prevent cramping, the centers of the lower ends of the leveling screws are in line with the center of the hemispherical nut, even when the leveling head is tilted far to one side. SHIFTING CENTER. The base plate is in two parts. The outer part is threaded to screw on the metal head of the tripod and the inner part encircles the hemis- pherical nut of- the leveling head. When the leveling screws are loosened the whole instrument can be moved so that the plummet may be precisely suspended over a desired point. The action of the leveling screws on the base plate as the instrument is leveled serves as a clamp, thus preventing any inadvertant shift after it is once set. TRANSIT INSTRUMENTS 43 THE TRIPOD. The tripod has a head of bronze with three strong tenons to receive the wooden legs, the upper ends of which are pressed firmly on each side of the tenon by a bolt and wing nut, which can be tightened by hand and thus kept firm. The lower end of each leg has a metal shoe with hardened point, securely fastened to the wood. There are four styles of legs the solid round leg, the split leg, the extension leg and jointed extension leg. For illustrations and descriptions see pages 238 to 242. INVITATION TO VISIT OUR FACTORY The extent of our business makes it impracticable for us to personally interview but a small number of our customers; therefore, we extend a cordial invitation to all of our friends to call on us whenever it is conven- ient to do so. It is our desire to become better acquainted and to more fully express our appreciation of the co-operation and good will which have so largely contributed to the success of our efforts. 44 W. & L. E. GURLEY, TROY, NEW YORK DISTINCTIVE FEATURES OF GURLEY TRANSITS Carley FIG. 10 No. 27-A PRECISE TRANSIT TRANSIT INSTRUMENTS 45 SELECTION OF TRANSITS VARIETY OF MODELS. As we make various models and sizes, it is possible to select an instrument which will suit every individual requirement. The differ- ence in prices does not indicate a difference in quality, as we make only one grade. The price is based on the actual cost of manufacture and, in each instance, it is the lowest for which a high grade and fully warranted instrument can be made. THE GURLEY PRECISE TRANSITS with patented One Piece Truss Standard and other new features represent the last word in design and construction and, as their name implies, they are adapted for work which demands the highest degree of accuracy and refinement. They are made in four sizes; the largest size is No. 18-A, Hell Gate Model; medium size, Nos. 6-A to 10-A and 10-A-3; the Light Mountain size, Nos. 25-A to 32-A; and the Explorers size, Nos. 20-A to 24-A. 46 W. & L. E. GURLEY, TROY, NEW YORK HELL GATE BRIDGE ERECTION CONTROLLED BY A GURLEY PRECISE TRANSIT THE BRIDGE OF THE NEW YORK CONNECTING RAIL- ROAD over the East River at Hell Gate stands as one of the most notable achievements in bridge engineering in recent years. It is a steel arch of 970 feet span and carries four tracks. The rapid tidal currents of the river and the neces- sity of maintaining a free passage for navigation during the construction made the use of false work impossible. The arch was built from the two abutments simultan- eously and its successful completion demanded that the ends of the two halves should meet in mid-stream with extreme exactness. This necessitated instrument con- trol of the very highest precision. The engineers who had this work in charge selected a Gurley Precise Transit and staked their engineering reputation on this choice. Their confidence in the instrument was justified when the cantilever members met within one-quarter of an inch of their predetermined position. Long base lines lateral to the structure were laid out on both shores. Concrete piers were built at the tri- angulation points, each pier having a permanent base for the Gurley Precise Transit which governed the work. Vertical and horizontal angles to 10 seconds were taken to panel points as erection proceeded, the exact TRANSIT INSTRUMENTS FIG. 11 No. 10-A PRECISE TRANSIT 48 W. & L. E. GURLEY, TROY, NEW YORK position of each point being accurately determined and checked bv observations from several stations. FIG. 12 VIEW OF HELL GATE BRIDGE DURING CONSTRUCTION TRANSIT INSTRUMENTS FIG. 13 No. 18-A PRECISE TRANSIT, HELL GATE MODEL 50 W. & L. E. GURLEY, TROY, NEW YORK PRECISE TRANSIT, HELL GATE MODEL This transit is of the Gurley One Piece Truss Standard construction and represents our supreme efforts. It is the result of seventy-five years experience in designing and building engineering instruments. It embodies all of the desirable qualities of our regular model Precise Transits and has the added advantages of the special features as shown in Fig. 13. Thus it is adapted for triangulation, bridge building, municipal engineering, etc., and for all classes of work demanding the highest degree of accuracy and refine- ment. Both the horizontal and the vertical limbs are grad- uated to 10 minutes and each reads by two opposite double verniers to 10 seconds. A rigid frame or guard protects the vertical circle and supports a long sensitive level which controls the zeros of the double opposite verniers, also supported by the frame. Microscopes suspended over each vernier facilitates the reading of the fine graduations. The telescope has an inverting eyepiece. MEDIUM SIZE PRECISE TRANSITS Transits with a 6.25" horizontal limb are listed as Nos. 6-A, 7- A, 8-A, 9-A, 10-A and 10-A-3, the numbers indicating different combinations of attachments, such as level on telescope, vertical circle or arc, and gradien- ter. The limb is graduated on sterling silver and reads by two opposite double verniers to single minutes. Finer graduations can be supplied at additional cost. TRANSIT INSTRUMENTS 51 The telescope is eleven inches long, erecting, and has a power of 26 diameters. The compass needle is 3^/2 inches long and has an arc for setting off the mag- netic declination. The instruments, without tripod, weigh from 15.5 to 16.5 pounds. Numbers 25-A, 26-A, 27-A, 28-A, 29-A, 30-A and 32-A apply to transits having a 5.65" horizontal limb. The telescopes have erecting eyepieces, a power of 20 diameters and are supported by our new One Piece Truss Standard. They are equipped with a three inch needle and weigh but eleven to thirteen pounds. Transits Nos. 25, 26, 27, 28, 29 and 30 also have a 5.65" horizontal limb. They are like Nos. 25-A to 32-A except that the telescope is supported by two separate standards and the compass needle is four inches long. Detailed specifications of all transits are given in a bulletin in the back of this Manual. 52 W. & L. E. GURLEY, TROY, NEW YORK THE GURLEY THREE SCREW LEVELING HEAD, as shown in Fig. 14, is of a design which gives the utmost rigidity without being cumbersome and provides a shift- ing center of liberal movement. Spiral springs are not used in the construction of this head which can be immovably clamped before angle reading is started. Our instrument need not be de- tached from the tripod when being carried between stations. The three screw leveling head is made only to order. It can be furnished with any RCW T Gurley Transit, if desired, at an extra cost. TRANSIT INSTRUMENTS 53 FIG. 14 No. 10-A-3 PRECISE TRANSIT WITH THREE-SCREW LEVELING HEAD 54 W. & L. E. GURLEY, TROY, NEW YORK LIGHT MOUNTAIN TRANSITS THE GURLEY LIGHT MOUNTAIN TRANSIT. Its high grade construction and light weight have made this the most popular Gurley Transit, and in fact it is the ideal transit for all-around work. Although especially adapted for Mine and Mountain Surveys, it is used for Municipal, Highway and Railway Engineering as well as for Bridge and General Construction, Solar Observa- tions and Forest Surveys. It is the best knorvn transit in America and we stake our reputation on the results obtained from its use. It can be improved only by substituting in place of the two separate standards, our patented ONE PIECE TRUSS STANDARD. TRANSIT INSTRUMENTS 55 FIG. 15 No. 28 LIGHT MOUNTAIN TRANSIT The Best Known Transit in America 56 W. & L. E. GURLEY, TROY, NEW YORK THE GURLEY EXPLORERS PRECISE TRANSIT. This is the smallest and lightest Gurley transit but it is equal in quality and similar in construction to our Precise Light Mountain Transit and therefore can be used for work of a high degree of accuracy. As its name implies, it is designed for engineers working in a new or undeveloped country and also for those whose work is scattered and who are obliged to travel constantly. It is also used with great success by Mining Engineers who prefer or require a smaller and lighter instrument than the Light Mountain pattern. When placed in its leather-covered case it can be packed in a twenty-four inch dress suit case, together with its special jointed extension tripod. An Explorers Level, described on page 196, and an Explorers Alidade, described on page 249, can be included, in the suitcase, if desired. TRANSIT INSTRUMENTS 57 EXPLORERS PRECISE TRANSIT FIG. 16 No. 20-A EXPLORERS PRECISE TRANSIT The smallest and lightest Gurley Transit 58 W. & L. E. GURLEY, TROY, NEW YORK '- FIG. 17 EXPLORERS TRANSIT WITH ITS SPECIAL JOINTED EXTENSION TRIPOD, CANVAS CARRYING CASE, AND LEATHER COVERED WOODEN BOX TRANSIT INSTRUMENTS 59 FIG. 18 EXPLORERS TRANSIT, WITH ITS SPECIAL TRIPOD, PACKED IN A DRESS SUIT CASE 24 INCHES LONG 60 W. & L. E. GURLEY, TROY, NEW YORK RECONNOISSANCE TRANSIT The Gurley Reconnoissance Transit meets the de- mand for a very light instrument for rapid work. Constructed like our Mountain Transits, with long cen- ters and with ribbed leveling head,, limb and main plate, and made with the same care as our larger and more expensive patterns, it is recommended as reliable for a great variety of work. Its accuracy, its convenience in carrying, and its proved ability to stand up satisfactorily under severe use, have made this transit especially popular with Sur- veyors, Contractors, Road Engineers, Architects and Builders. TRANSIT INSTRUMENTS 61 FIG. 19 No. 102 RECONNOISSANCE TRANSIT 62 W. & L. E. GURLEY, TROY, NEW YORK CARE OF THE TRANSIT TOO much emphasis cannot be laid upon the impor- tance of care in handling and transporting instru- ments of precision. Every instrument as it leaves our factory is properly lubricated and adjusted ready for use. It will remain so for a long time, if treated as an instrument of precision. HANDLING THE INSTRUMENT. Extreme care must be taken at all times to prevent the instrument from receiv- ing shocks which may throw it out of adjustment. When shipped for any distance the instrument case should be enclosed in an outer packing box and carefully sur- rounded with some shock absorbing material. If any- thing dusty, as excelsior, is used, the case should first be wrapped in paper with the edges pasted to keep out the dirt. When not in use, the instrument should be placed in its case. When carrying the instrument mounted on the tripod, through brush, or through doors of a building or similar places, the tripod should be carried under the arm and not over the shoulder, thus avoiding the possibility of accidently striking the instru- ment. When setting up the instrument, the tripod should not be set too high, as it may be easily tipped over. Particular care should be given to this feature when setting the tripod on steps or on a hillside where one leg is generally shortened and placed at a high angle. In handling the instrument, care should be taken to grip it at such points that no strain will be put on any of the adjustments. The Gurley method of packing TRANSIT INSTRUMENTS 63 transits prevents any lateral strain from being placed upon the spindle, sockets, or standards. To remove the transit from the box, first lift out the packing pieces from the ends of the telescope axis, grasp the tops of the standards with both hands, or the telescope axis with one hand, and lift the instrument out of the box. To place upon the tripod, unscrew the leveling fcead clamp, lift the instrument and with the fingers under the limb or body and the thumbs on the top plate, set upon the tripod. Retain the grasp with one hand and with the other, screw the bottom plate on the tripod head. The transit may also be lifted from the box by turn- ing the telescope to a vertical position, reaching down into the box and grasping it under the limb as described above. This method has the advantage that the transit may be placed directly upon the tripod without chang- ing the hands. It should never be lifted by taking hold of the standards except as described above, nor should it be lifted or carried by means of the leveling head, leveling screws or bottom plate, when not on the tripod, without being steadied near the top. Before attempting to turn the transit in either of the sockets, be sure that at least one of the clamp screws has been loosened. Turn the transit by means of the lower part of the standards, the plate or the tangent attachments, but not by the telescope. In tightening clamp screws it is necessary only to screw them home lightly, as the design of Gurley clamps makes them grip very firmly. If too much force is 64 W. & L. E. GURLEY, TROY, NEW YORK applied to the clamp screw, the thread will be strained and worn unnecessarily. All bearing surfaces are made as nearly frictionless as possible and therefore need very little lubrication. If it does become necessary to lubricate a thread or bearing, only the best grade of watch oil should be used and only a very small amount of that. A thin film of light oil is all that most of the fitted surfaces will admit. Oil should be carefully wiped from exposed parts, as it will cause dust to adhere. CLEANING THE INSTRUMENT. So far as possible, all outside cleaning or dusting of instruments should be done with a soft camel hair brush. Care should be taken not to rub the lacquer from the finished surfaces, as the exposed metal will readily tarnish. Alcohol, or similar solvents should never be used on the instru- ments. In cleaning the lenses, first remove the dust with a soft brush and then wipe lightly with a soft, dry cloth, free from lint. Rubbing the lenses dry sometimes causes small particles to stick to them, and, in this case, blowing the breath on the glass will furnish sufficient moisture so that they may be rubbed off easily. If any liquid is brought into contact with the lenses, it is liable to penetrate the mounting and give bad results. Do not rub the silver upon which the graduations are cut, as this will make bright spots, which cause difficult reading. Particular care must be taken to prevent anything from coming into contact with the graduated edge, not TRANSIT INSTRUMENTS 65 even rubbing this with a soft cloth. As this is solid silver, it is soft and easily damaged. If necessary to clean the limb, dampen a soft cloth, dip it in powdered charcoal, and rub lightly over the silver, being careful not to rub over the graduated edge. DISMOUNTING THE INSTRUMENT. In case of damage to the instrument, it should, if possible, be returned to the maker for repairs. If absolutely necessary, how- ever, to take the instrument apart, it should be done in some place which is free from dust; never out in the open where dirt may be blown into the working parts as they are being assembled. REMOVING THE OBJECTIVE LENS. Unscrew the dust guard on the end of the main tube and then unscrew the small ring in the end of the slide head. This brings with it the complete lens in its setting. The objective consists of two lenses held together by two metal rings. The former are marked on the edge with a cross so that they may be put back together in the same relative posi- tion. It is always necessary to check all adjustments of the telescope after the objective lens has been loosened or removed. REMOVING THE EYE PIECE. If there is an eye piece pinion, first take out the two screws holding it to the telescope and pull the pinion straight out from the tube. Take out the eye piece centering screws, A A, Fig. I, unscrew the eye end ring, L, and withdraw the eye piece from the tube. The eye piece lenses may be separately cleaned, and, if put back as found, no adjust- ments will have been destroyed. 66 W. & L. E. GURLEY, TROY, NEW YORK CROSS WIRE DIAPHRAGM. If necessary to replace a cross wire in the field, the eye piece must first be re- moved, as described above. With the telescope in a horizontal position, first take out two side adjusting screws, B B, Fig. I, and by means of the remaining screws turn the diaphragm through an angle of 90, so that the edge points toward the end of the telescope. Place a small stick or pencil in the screw hole in the side of the diaphragm, take out the remaining screws and pull out the diaphragm. If the diaphragm has adjustable stadia wires the stadia screws must first be loosened. COMPASS NEEDLE. The closed top over the compass may be removed by unscrewing the bezel ring from right to left. When replacing the needle on its center, it should be lowered very gently into position to prevent damage to the finely polished point. THE OBJECTIVE SLIDE. Take out the four screws from the pinion strap, pull the pinion straight out from the tube, and the slide may be withdrawn from the telescope. LEVEL VIALS. Take the levels from the plate, or the telescope, and remove the ends. These screw on for the larger sizes, but simply push in the vial tube, for the smaller sizes. Soak the plaster of paris with water, scrape or cut it out, and push out the old vial. If the new vial fits loosely, it should be fixed in place with slips of paper before being plastered. Take care that the crowning side of the vial, which is graduated, is placed uppermost and see that the sealed tip will not be touched TRANSIT INSTRUMENTS 67 when the end of the case is replaced. If plaster of paris is not available, beeswax or some other heavy wax may be used temporarily to hold the vial, but, as this softens on a warm day, it should replaced by plaster of paris at the first opportunity. The sealed tip should be left uncovered. To SEPARATE THE PLATES. Unscrew the tangent barrel, taking care that the tangent slide and spring do not drop out. Take the small screws from the tangent hanger and remove the latter from the plate. If the lower plate or limb is to be removed, the lower tangent barrel with slide and spring should be removed from the leveling head tangent. Remove the cap (if there is one) from the bottom of the spindle, take out the large screw and washer, and the plate may then be removed from the sockets. The most extreme care must be used in replacing the sockets and spindles to see that not the slightest parti- cle of lint or dust gets into the bearing. To lubricate these surfaces, rub a small amount of the very best watch oil on a clean cloth free from lint, and rub over the surfaces to be lubricated. A heavy oil will separate these bearings so far that proper adjustment cannot be maintained. THE REPAIRS. Attention is again called to the fact that a damaged instrument should not be repaired in the field. If any parts have been injured the best way is to return the whole instrument to us for proper repairs. Such repairs can be made with less trouble and less cost if no attempt has been made to dismount the instrument in the field to determine the extent of the damage. 68 W. & L. E. GURLEY, TROY, NEW YORK USE OF THE TRANSIT THE instrument should be set up firmly, the tripod legs being pressed into the ground only so far as is necessary to give sufficient support. The legs should be spread apart far enough so that the transit cannot be easily knocked over. The height of the instru- ment should be adjusted for convenient sighting by the operator. The plate should then be carefully leveled, as described hereinafter under level adjustments. For precise work the final leveling of the plates should be made with the telescope level, placing it in turn over the two pairs of opposite leveling screws. In reversing the level, one half of the correction should be made with the axis tangent and the other half with the leveling screws, the same as in the adjustment for plate levels. With the telescope pointed toward the sky, or out of focus, turn the eye piece pinion or the spiral until the cross wires appear distinct, then the objective should be focused until the object is seen, clear and well defined, and the wires appear to be fastened to its surface. If the objective is properly focused so that the plane of the image coincides with the plane of the cross wires, the latter will not appear to move on the object when the eye is moved up and down in front of the eyepiece. When the horizontal angles are to be measured the zeros of the verniers and limb should be in line with the upper motion. Clamped in this position, the telescope should be sighted on a distant point by means of the lower or leveling head motion. After this has been done and 'with the lower motion clamped, loosen the upper TRANSIT INSTRUMENTS 69 motion on limb clamp and the angles turned may be read directly from the verniers without making any sub- tractions. When the compass is to be used, set the variation arc to the proper magnetic declination by means of the pinion on the plate. The value of magnetic variation for any given locality can be obtained from the publica- tions of the U. S. Geological Survey, Washington, D. C. If the needle does not hang level when at rest, re- move it from the pivot and slide the small brass wire, which is on the South end (in the Northern hemisphere), in the proper direction to obtain a balance. STADIA SURVEYING The increasing popularity of the stadia for the deter- mination of distances and differences in elevation is due to its widening field of application, together with a better appreciation of its reliability through a clearer under- standing of the principles involved. So much has been written regarding the theory of the stadia and so little as to its practice, that there is need of a condensed statement of the most approved pro- cedure in stadia work. The instrumental outfit embraces any mounted tele- scope fitted with stadia wires and a vertical arc or circle, and while any leveling rod may serve for occasional stadia work, a regular stadia rod of some approved type should be used for good work, and must be used for sat- isfactory results at distances exceeding 400 feet. In all cases, simplicity rather, than jnultiplicity of subdivision * WTVERSlTr OF CALIFORNIA is a prime requisite. -fiFARTMENT OF CIVIL ENGINES*!* 70 W. & L. E. GURLEY, TROY, NEW YORK STADIA CONSTANT. The use of the stadia when measuring short distances with great accuracy, compels the use of the so called "Stadia Constant." The wires are generally adjusted to read one foot on the rod at a distance of one hundred feet from a point in front of the telescope objective equal to the focal length of the lens (f), Fig. 20. Since measurements are taken from the center of the instrument, it is therefore necessary to add to the stadia reading, the distance C, from the center of the axis to the shoulder of the objective setting when focused at the distance to be measured, plus the distance F, from the objective lens to the plane of the stadia wires, when the instrument is focused at a distant ob- ject (not less than 1000 feet) which gives the focal length of the lens. The sum of these two distances (F -(- C), is the Stadia Constant, which must be added to all stadia measurements regardless of the distance measured. This constant is carefully measured in the factory for each instrument, and its value is marked on a card placed in the instrument box. For example, in our eleven inch telescope, such as are used with the larger transits, C equals about 5.6 inches and F, about 8.2 inches; and C -f- F is equal to about 1.15 feet. For the Mountain Transit telescopes, C equals 4 inches and F, 5.4 inches, and C -f- F equals about 0.783 foot. The reason for the use of this constant will be seen by reference to Figure 20. TRANSIT INSTRUMENTS 71 With the telescope focused upon the rod: Let i = interval between the stadia wires c = distance from center of transit to objective lens f = focal length of objective lens s reading on the rod, or space intercepted on rod by stadia wires Outer focus = a point in front of the lens and F dis- tance from it d ==. distance from the outer focus to the rod From the definition of focal length, those rays of light passing through the outer focus are refracted by the lens to parallel paths. Those which pass through this point and intercept the stadia wires are i distance apart at the lens. Then from similar triangles (1) d/s = f/i, or d = f/is since f/i is a constant for any given instrument, we may represent it by K (2) and d = Ks 72: W. & L. E. GURLEY, TROY, NEW YORK Since the measurements are made from the center of the instrument, we must add F + C, and the total dis- tance is D = Ks + (F + C) (F -]- C) is called the Stadia Constant and K is made 100 feet. Therefore, if f -)- c = 1.2 feet, a subsequent reading of 540 feet would indicate a distance of 541.2 feet from plumb line to rod. The undue consideration of this very small f -(- c constant has too often caused the relative neglect of a far more important one, and we wish here to emphasize the latter. It is either the necessity for extreme accuracy in ad- justing the stadia wires to give the desired proportion of 1 to 100, or, in the case of measurements calling for greatest precision, the necessity for determining the stadia interval or factor, i. e., K. K = f/i = d/s = 100 This factor should be a mean result of rod readings at steel-taped distances of say 400 and 700 feet from a point f -f- c in front of the center of the instrument. E. g., observed readings of 395.2 and 693.0 feet would give (dividing by 400 and 700) proportions of 98.8 and 99.0 to 1, respectively, and a corresponding mean inter- val factor of 101.11 (100 divided by the mean propor- tion 98.9), which, multiplied by subsequent field read- ings, would bring the observed distances up to the correct ones. Thus, if f + c = 1.2 feet, an observed distance of 230 feet could be treated as follows: (230 X TRANSIT INSTRUMENTS 73 1.0111) + 1.2 = 233.75 feet true distance from center of instrument to rod. In practice, however, a small reduction table can be quickly prepared to give these corrected distances for every 10 feet up to 100, then each 100 feet up to 1,000, etc. This table may include or exclude the f -|~ c constant. Stadia wires are sometimes set so that the reading indicates the exact figure including the stadia constant for some one distance, and the slight error for other dis- tances is disregarded. STADIA WORK WITH INCLINED SIGHTS. If the tele- scopic line of sight is inclined to the horizontal, the distance as read from the rod must be corrected accord- ing to the vertical angle indicated by that pointing. The same data, vertical angle and observed distance at that pointing are used to compute difference in elevation between instrument and rod. The lod should be held vertical, which makes the operations simpler and in general more accurate. To facilitate both these operations various stadia tables, diagrams and slide rules have been devised. They are all based upon the well known stadia formulae, which, for practical purposes, may be expressed as: d = s cos 2 v + (f + c) cos v (1) h = s % sin 2 v -f- (f _|_ c ) sin v (2) where s = observed stadia distance v = measured vertical angle d = required distance from center of instrument to rod h = required difference of elevation between instru- ment and point sighted on rod. 74 W. & L. E. GURLEY, TROY, NEW YORK Stadia diagrams or charts give the difference in ele- vation and also the reduced horizontal distance, graphic- ally, at a point in the chart which is found at the intersection of two lines, one representing the measured angle and the other the observed distance. Stadia slide rules involve setting the slide to corres- pond to the angle and then reading off, opposite the denoted distance, the desired results. We furnish with each instrument having stadia wires, but no Beaman Stadia Arc, a celluloid circular slide rule known as the Cox Stadia Computer. THE BEAMAN STADIA ARC affords a rapid and exact mechanical solution of these functions without the necessity of the measurement of the usual vertical angle and without recourse to either tables, charts or slide rules, and with but trifling computation. This practical and inexpensive patented attachment for transits and alidades is controlled by us and is described on pages 90 to 96. SUGGESTIONS FOR STADIA WORK. The accuracy of all stadia work is directly proportional to the ease, care and accuracy with which the observed stadia distance has been read. If either focus is poor, if the rod is indistinct by reason of too great distance or other cause, or if the rod is not held plumb, the observed distance is uncertain, and, therefore, good results cannot be ex- pected. The greater the vertical angle, the greater the error due to the rod not being held plumb. TRANSIT INSTRUMENTS 75 Secure such a focus on wires as will give no apparent displacement of object when stadia wires are in sharp focus for the observer and when objective is focused on object and eye is moved up and down in front of eye- piece; i. e., see that there is no parallax. The instrumental adjustments to be made are for collimation and level tube. When the air is unsteady or "boiling," remember that the greatest refraction in the line of sight occurs in the lower air stratum. Therefore, at these times avoid so far as possible reading a distance in which the lower wire is nearer the ground than two or three feet. For refined work, determine the stadia factor, K, under such conditions as will approximate those to be expected in field practice. The mid- forenoon or after- noon is preferable to midday. For elevation work with inclined sights, note the necessity for extreme accuracy in the observed distance when the vertical angle is large, and the necessity for a carefully determined angular value when the distance is great. THE GRADIENTER ATTACHMENT No. 150, which may be used to advantage in all stadia work is fully described on pages 96 to 100. 76 W. & L. E. GURLEY, TROY, NEW YORK TO ADJUST THE TRANSIT EACH Gurley instrument leaves the factory in com- plete adjustment, but some adjustments are liable to derangement by accident or careless use. We describe particularly those which are most likely to need attention. The principal adjustments of the transit are the, Plate Levels Line of Collimation Standards Objective Slide Vertical Circle Vernier Level on Telescope To ADJUST THE PLATE LEVELS. Set the instrument upon its tripod as nearly level as may be, and having undamped the plates, bring the two levels above, and on a line with, the two opposite leveling screws, and, turn- ing both in or out, as may be needed, bring the bubble of the level directly over the screws exactly to the middle of the opening. Without moving the fnstrument, proceed in the same manner to bring the other bubble to the middle. The level first corrected may now be thrown a little out; if so, bring it in again, and when both are in place, turn the instrument half way around. If the bubbles are both in the middle they need no cor- rection ; but if not, turn the nuts at the end of the levels with the adjusting pin, until the bubbles are moved over half the error. Bring the bubbles again into the middle by the leveling screws, and repeat the operation until the bubbles will remain in the middle during a complete TRANSIT INSTRUMENTS 77 revolution of the instrument. The leveling screws should be kept free at first, gradually tightening them as final adjustment is approached. To ADJUST THE LINE OF COLLIMATION. This adjust- ment is to bring the cross wires into such a position that the instrument, when placed at the middle of a straight line, will, by the transit of the telescope, cut the extrem- ities of the line. Having leveled the instrument, deter- mine if the vertical wire is plumb, by focusing on a defined point and observing if the wire remains on that point when the telescope is elevated or depressed. If not, loosen the cross wire screws, BB, see Fig. 1, and by their heads turn the ring until correct. The open- ings in the telescope tube are slightly larger than the screws, so that when the latter are loosened the ring can be rotated a short distance in either direction. Direct the intersection of the cross wires on an ob- ject two or three hundred feet distant. Set the clamps, and transit to an object about the same distance in the opposite direction. Unclamp, turn the plates half way around, and direct again to the first object; then transit to the second object. If it strikes the same place, the adjustment is correct. If not, the space which inter- venes between the points bisected in the two observations will be double the deviation from a true straight line, since the error is the result of two observations. In the diagram, Fig. 21, let A represent the center of the instrument, and B C the imaginary straight line, upon the extremities of which the line of collimation is to be adjusted. B represents the object first selected, 78 W. & L. E. GURLEY, TROY, NEW YORK and D the point which the wires bisected when the tele- scope was reversed. D FIG. 21 When the instrument is turned half around, and the telescope again directed to B, and once more reversed, the wires will bisect an object, E, situated as far to one side of the true line as the point, D, is on the other side. The space, D E, is therefore the sum of two deviations of the wires from a true straight line, and the error is made apparent. In order to correct this, use the two capstan head screws BB, Fig. 1, on the sides of the telescope, these being the ones which affect the position of the vertical wire. It must be kept in mind that the eyepiece appar- ently inverts the position of the wires, and therefore, in loosening one of the screws and tightening the other on the opposite side, the operator must proceed as if to increase the error observed. The wires being adjusted, their intersection may now be brought into the center of the field of view by moving the screws, A A, which are slackened and tightened in pairs, the movement being now direct, until the wires are seen in their proper position. The position of the line of collimation depends upon the relative position of the objective and the cross wires, TRANSIT INSTRUMENTS 79 so that the eyepiece may, as in the case just described, be moved in any direction, or even removed and a new one substituted, without at all deranging the adjustment of the wires. To ADJUST THE STANDARDS. In order that the point of intersection of the wires may trace a vertical line as the telescope is elevated or depressed, it is necessary that the standards of the telescope should be of precisely the same height. That is the center line of the horizon- tal axis must lie in a plane perpendicular to the center line of the spindle. To ascertain this, and make the correction, if needed, proceed as follows: Having the line of collimation properly adjusted, set up the instrument in a position where points of observa- tion can be selected, giving a long range in a vertical direction, such as the apex and base of a lofty spire. Level the instrument, direct the telescope to the top of the object, and claim) to the spindle; then bring the telescope down until the wires bisect some well defined point at the base. Turn the instrument half around, reverse the telescope and direct to the lower point, clamp to the spindle, and raise the telescope to the highest point. If the wires bisect it, the vertical adjustment is effected; if they are thrown to either side, this proves that the standard opposite to that side is the highest, the apparent error being double that actually due to this cause. To correct it, we make one of the bearings of the axis movable, so that by turning a screw underneath this sliding piece, as well as the screws which fasten the cap of the standard, the adjustment is made with pre- 80 W. & L. E. GURLEY, TROY, NEW YORK cision. If the standards adjustment is altered, it is necessary to again adjust the line of collimation. Besides the three adjustments described, which are all that the surveyor will ordinarily be required to make, there are other adjustments of the transit which may sometimes be necessary. To ADJUST THE OBJECTIVE SLIDE. In case of acci- dent or injury, it may be necessary to adjust the objec- tive slide, and this should be done as follows. First make sure that the vertical wire is as nearly plumb as it is possible to make it. Having set up and leveled the instrument, the line of collimation being adjusted for objects from three hundred to five hundred feet distant, clamp the plates, and fix the vertical cross wire upon an object as distant as may be distinctly seen. Without disturbing the instrument, move out the objective so as to bring the vertical wire upon an object as near as the range of the telescope will allow. Having this object clearly in mind, loosen the upper clamp, turn the instru- ment half way around, reverse the telescope, clamp the instrument, and with the tangent screw bring the vertical wire again upon the near object; then draw in the objec- tive until the distant object first sighted upon is brought into distinct vision. If the vertical wire strikes the same line as at first, the slide is correct for both near and remote objects, and, being itself straight, is correct for all distances. But if there is an error, proceed as follows: With a screw driver turn the two screws, CC, Fig. 1, on the opposite sides of the telescope, loosening one and tight- TRANSIT INSTRUMENTS 81 ening the other, so as to apparently increase the error, making, by estimation, one half the correction required. Then go over the usual adjustment of the line of collim- ation, and, having completed it, repeat the operation above described, first sighting upon the distant object, then upon a near one in line, then reversing, making cor- rections, etc., until the adjustment is complete. This adjustment is a distinctive feature of Gurley transits and furnishes the only way in which the line of collimation can be correct for all distances. To ADJUST THE VERTICAL CIRCLE VERNIER. Having the instrument firmly set up and carefully leveled by means of the telescope level, bring into line the zeros of the circle and vernier, and with the telescope find some well defined point, from one hundred to five hundred feet distant, which is cut by the horizontal wire. Turn the instrument half way around, transit the telescope, and fixing the wire upon the same point as before, ob- serve if the zeros are again in line. If not, loosen the capstan head screws which fasten the vernier, and move the zero of the vernier over half the error; bring the zeros again into coincidence, and proceed exactly as be- fore, until the error is entirely corrected. In most cases the error is slight and may be best removed by putting the zeros in line and making the adjustment by the horizontal wire, moving it by the vertical capstan head screws until the vertical circle will reverse on the same point. To ADJUST THE LEVEL ON TELESCOPE. When the vernier of the vertical circle is adjusted and is at zero, 82 W. & L. E. GURLEY, TROY, NEW YORK the line of collimation is level and the bubble may be brought into the middle of its run by the capstan head nuts. Another method is as follows: First level the instru- ment carefully, using the telescope level and with the clamp and tangent movement to the axis make the tele- scope as nearly horizontal as may be, by the eye. Then, having previously adjusted the line of collimation, drive a stake at a convenient distance, say from one hundred to three hundred feet, and note the height cut by the horizontal wire upon a staff set at the top of the stake. Fix another stake in the opposite direction and at the same distance from the instrument, and without dis- turbing the telescope turn the instrument upon its spindle, set the staff upon the stake, and drive the stake into the ground until the same height is indicated as in the first observation. The tops of the two stakes will then be in the same horizontal line, however much the telescope may be out of level. Remove the instrument from fifty to one hundred feet to one side of either of the stakes and in line with both. Again level the instrument, clamp the telescope as nearly horizontal as possible, and note the heights indicated upon the staff placed first upon the nearest and then upon the 'most distant stake. If both agree, the telescope is level. If they do not agree, with the tan- gent screw move the wire over nearly the whole error, as shown at the distant stake, and repeat the operation just described. Proceed thus until the horizontal wire will indicate the same height at both stakes, when the TRANSIT INSTRUMENTS 83 telescope will be truly horizontal. Taking care not to disturb the position of the telescope, bring the bubble into the middle by the leveling nuts at the end of the tube, when the adjustment will be complete. REPAIRS. When an instrument becomes worn from service or is injured by a fall or accident of any kind, it is, of course, necessary to have it repaired and refitted before anyone can adjust it. An instrument in need of repairs should be sent directly to us, as our facilities enable us to do the work economically and promptly. Always place the instru- ment in its own case, wrap with paper, then enclose in an outside packing case, at least an inch larger in all its dimensions and fill the space between the two with paper wadding, hay or shavings. ATTACHMENTS FOR TRANSITS IN the use of the transit it is generally found advisable to add one or more attachments to the telescope. All Gurley transits and their attachments are made to standard sizes, so that one or more of these useful accessories can be fitted to the instrument at any time. When any of these attachments are desired, either for our instruments or those of other makers, the instru- ment must be sent to us. Occasionally they can be added by a skillful mechanic nearer the customer, but this is generally more expensive and less satisfactory. 84 W. & L. E. GURLEY, TROY, NEW YORK The principal attachments for the transit are described on the following pages, and are: VERTICAL CIRCLE (see pages 85 to 87). GUARD FOR VERTICAL CIRCLE (see page 85). VERTICAL ARC (see page 88). LEVEL ON TELESCOPE (see page 89). BEAMAN STADIA ARC (see pages 90 to 96). GRADIENTER, COMBINED WITH CLAMP AND TANGENT (see pages 96 to 100). DETACHABLE TELESCOPES FOR VERTICAL SIGHTING (see pages 101 and 102). REFLECTOR FOR ILLUMINATING THE CROSS WIRES (see page 103). DIAGONAL PRISM FOR EYEPIECE OF TELESCOPE (see page 103). PLUMMET LAMP (see page 104). ATTACHED MAGNIFIERS TO HORIZONTAL OR VERTICAL LIMB (see page 106). BURT SOLAR ATTACHMENT TO TELESCOPE (see pages 114 to 136). SOLAR SCREEN (see page 106). TELESCOPIC SOLAR ATTACHMENT (see pages 136 to 144). TRANSIT INSTRUMENTS 85 FIG. 22 No. 136 VERTICAL CIRCLE, WITH No. 141 ALUMINUM GUARD THE VERTICAL CIRCLE. Vertical Circle, No. 136, is graduated on sterling silver and figured in quadrants to 90 each way. We make three sizes, four inches, four ai-d one-half inches and five inches in diameter, all reading by one fixed vernier to single minutes. There is an adjustment on the hub by which the grad- uations are as accurately and permanently centered as those of the horizontal limb. 86 W. & L. E. GURLEY, TROY, NEW YORK FIG. 23 No. 138 VERTICAL CIRCLE, WITH TWO OPPOSITE DOUBLE VERNIERS, AND GUARD The four inch and five inch vertical circle may be arranged as shown in No. 138, to be read by two opposite double verniers to one minute. The verniers are sup- ported on a ribbed frame or guard in such a manner that the circle is concentric with the frame, and the verniers read accurately in any position of the circle. The frame is arranged with an adjusting screw, to bring the verniers into exact adjustment with the level on the telescope. TRANSIT INSTRUMENTS 87 Fm. 24 No. 139 VERTICAL CIRCLE, 4.5 INCHES DIAMETER, WITH GRADUATIONS ON EDGE OR RIM, PROTECTED BY A METAL GUARD. CIRCLE GRADUATED TO HALF DEGREES, WITH VERNIER READING TO 1 MINUTE. If desired the vertical circle can be graduated on the edge or rim, so that the vernier is visible in front of the observer without a change of position. As on No. 138 the vernier is attached to the guard, instead of to the standard. The adjustment is made in the same manner as it is on the regular pattern, No. 136. GUARD FOR VERTICAL CIRCLE. All transits having a vertical circle should be equipped with a guard, to protect the graduated edge of the circle. We make an 88 W. & L. E. GURLEY, TROY, NEW YORK improved guard, shown in No.141, Fig. 22, of aluminum, morocco finished, mounted on the standard concentric with the circle and attached so that it can be removed or put in place without affecting the adjustment of the circle. FIG. 25 Nos. 139-A, 139-B AND 140 VERTICAL ARCS VERTICAL ARC. The Vertical Arc is made in three sizes, of two, two and one-half, and three inches radius. It is graduated on sterling silver and reads by vernier to one minute. The vernier is swung from the axis and is movable by a tangent screw. The arc is less liable to damage than the full circle. It was first introduced to allow the Burt Solar Attach- ment to reverse. On Gurley Transits the arc is movable around its bearing on the axis, and it may be clamped at approximate zero when the telescope is level and the vernier brought to exact coincidence of zero, by a tan- TRANSIT INSTRUMENTS 89 i gent screw that moves the vernier only. This Gurley feature prevents any damage to the arc when the tele- scope is used in the reversed position. Any vertical angle can then be read directly on the arc. This arc can be readily attached to any transit of our manufac- ture. FIG. 26 No. 145 LEVEL ON TELESCOPE LEVEL ON TELESCOPE. The Level on Telescope, No. 145, consists of a brass tube about six and one-half inches long, each end of which is held between two cap- stan nuts connected with a screw or stem attached to the under side of the telescope tube. The vial enclosed in the tube is a little over five inches long and half an inch in diameter, and is ground on its inner surface so as to insure an even movement of the bubble, the length of which is measured by a scale etched on the glass. The scale is graduated to two millimeters. 90 W. & L. E. GURLEY, TROY, NEW YORK When required we supply a tube with a double open- ing, and a Reversion Level Vial, No. 146, that can be used either side up with equal facility. Special attention is called to the Gurley feature of having the level vial as nearly as practicable the full length of the telescope. This gives increased accuracy in leveling operations. To adjust the level on telescope, see method described on page 81. SIGHTS ON TELESCOPE AND ON STANDARDS. For con- venience in observation, we occasionally place a pair of small sights, No. 157, on the telescopes of our transits. These sights have folding joints, that they may lie close to the telescope when not in use. Sights, No. 158, may also be placed on the standards at an angle of ninety degrees with the telescope, for use in offsetting. BEAMAN STADIA ARC THE Beaman Stadia Arc is manufactured only by W. & L. E. Gurley, was devised and patented by W. M. Beaman, a topographer in the United States Geological Survey, and is now extensively used by that bureau in its topographical surveys. In 1906 we introduced it on our transits and alidades, and because this arc furnishes engineers with a rapid and exact mechanical solution of the stadia problem, the use of the stadia in surveying has been popularized to an appreciable extent. By the use of this arc precise differences in elevation, and reduced horizontal distances can be determined with TRANSIT INSTRUMENTS 91 great rapidity, and without the intricate calculation here- tofore necessary. The arc is attached to the vertical limb of the transit Fig. 9, or alidade Figs. 97 and 98, and carries two scales having coincident zero points, marked and 50 respec- tively, either scale being read by an index common to both. The scale graduations are so spaced and figured as to give simple multiples of the rod interval. The Beaman Stadia Arc can also be used for metric measurements, as the graduations are based on a ratio of 1 to 100, which is 1 foot to 100 feet, or 1 meter to 100 meters. The stadia constant should be transposed to meters, however, when this unit is used. ADVANTAGES OF THE BEAMAN STADIA ARC 1. The use of stadia tables, slide rules, or diagrams is entirely obviated. 2. There is no vernier or similar contrivance to be read. 3. Final results are obtained in less than one-third the time required by ordinary methods. 4. The accuracy of results is identical with formulae or table computations, regardless of the angle or distance. 5. The simplicity of the process practically eliminates the chances of error incidental to the use of other methods. 92 W. & L. E. GURLEY, TROY, NEW YORK H V 0-5Q- 66: FIG. 27 GRADUATIONS OF BEAMAN STADIA ARC The Beaman Stadia Arc can be supplied with any new transit or tele- scopic alidade of our manufacture having a vertical limb of either a one vernier vertical circle, a two vernier circle, or a vertical arc. This attachment can also be fitted to any old Gurley transit or telescopic alidade, but the additional cost of alterations and readjusting can only be determined upon examination of the instrument, which must be in our hands for this purpose. For view of the graduations of the Beaman Stadia Arc as applied to tele- scopic alidades, see Fig. 27. To obtain difference in elevation between instrument and rod the scale marked Vert, is used. This scale indicates multiples of the rod interval, for determining differences in elevation between instrument and rod. The zero point of this scale is marked 50, so a scale reading less than 50 indicates that the telescope is de- pressed, while a reading greater than 50 shows that the telescope is elevated. TRANSIT INSTRUMENTS 93 A unique feature of the use of the multiple scale is that only such inclinations of the telescope need be used as will give a whole number vertical scale reading, while the fractional part of the elevation is shown by the rod reading. To obtain the desiied multiple, therefore, sight any- where on the rod, it does not matter where, so that a whole number reading is obtained on the multiple scale. Subtract 50 from this scale reading and use the alge- braic remainder; e. g., if the Vert, scale reads 56, the multiple is 56 50= -|- 6. If this scale reads 47, the multiple is 47 50= 3. Example: Suppose the observed subtended stadia reading on the rod to be 6.40 (640 ft.), and to obtain a whole number for the scale reading, the telescope is inclined so that the multiple scale reads 33, at which setting the middle wire reads 7.30 on the rod. Then the desired multiple equals 33 50 = 17 and 17 X 6.40 = 108.8 Difference in elevation between instrument and base of rod is then, 7.30 108.8 = 116.1 ft. The negative sign indicates that the point where the rod was held is lower than the instrument. For accurate work at the higher angles it is also necessary to add to the difference in elevation the cor- rection for the stadia constant, f -[- c. This correction is (f -f- c) sin vertical angle. 94 W. & L. E. GURLEY, TROY, NEW YORK THE TRUE HORIZONTAL DISTANCE is found by means of the scale marked "Hor.", which gives at the same pointing a direct reading of the percentage of correction (always subtractive) necessary to reduce the observed stadia reading (in feet subtended) to the true horizontal distance. Example: At the above setting the reduction scale would read 3, or 3%. 3% of 640 ft. = 19.2 ft. 640 19.2 = 620.8 ft., the true horizontal distance. If the accuracy desired requires the use of the stadia constant, (/ -f- c) cos vert, angle should be added to the horizontal distance as determined above. A FORM OF NOTES FOR USE WITH BEAMAN STADIA ARC (Reprinted by permission of United States Geological Survey} To facilitate the slight computation necessary to determine differences in elevation, a special form of notes has been devised for use with this attachment. Stadia Arc Reading Distance Product Rod Correction Difference of Elevation Elevation Station B. S. F. S. 654.7 B. M. 54 4.2 - 16.8 + 8.2 8.6 646.1 H. I. 48 6.3 12.6 4.9 17.5 628.6 T. P. 44 9.2 + 55.2 + 4.3 +59.5 688.1 H. I. 57 15.8 +110.6 13.8 +96.8 784.9 T. P. 50 8.4 + 6.7 + 6.7 791.6 H. I. 50 5.6 9.8 9.8 781.8 T. P. TRANSIT INSTRUMENTS 95 The Beaman Arc reading is placed under the appro- priate heading, B. S. or F. S., in the above table. All sights are to be regarded as foresights, except those taken to determine the H. I. Thus, after a B. S. has been taken to determine the H. I., all intermediate rod stations, whether taken before the rod reaches the instru- ment or after the rod goes ahead, are to be entered as foresights. The distance is recorded as 4.2, 6.3, etc., meaning 420 feet, 630 feet, etc. The column headed "Product" is for the multiple times the distance; for example 4 X 4.2 16.8; 4 being the multiple for a stadia arc setting of 54. The column headed "Rod Correction" is for the final reading of the middle wire on the rod. The signs to be affixed to the "Product" and to the "Rod Correction" are determined according to whether the observation is a B. S. or a F. S., by following a rule of universal application, namely : Product Rod Correction B. S. F. S. Opposite sign to that indicated by arc reading... Same sign as that indicated by arc reading + A stadia arc reading of 54 indicates -j- ; therefore, here the sign of the "Product" is for a B. S., and -f- for a F. S. Note that the sign of the "Rod Correction" is the same as in leveling. When the line of sight is level, the stadia reading is 50, and hence the multiple is 0, which gives a "Product" 96 W. & L. E. GURLEY, TROY, NEW YORK 0. The only entry is, therefore, the "Rod Correction," or the final rod reading, whose sign follows the above rule. Take the "Product" and the "Rod Correction" by pairs, and add algebraically; e. g., 16.8 -f- 8.2= 8.6, the "Difference of Elevation." This, applied algebrai- cally to the last known elevation, gives the elevation desired. GRADIENTER FIG. 28 No. 150, GRADIENTER TRANSIT INSTRUMENTS 97 THE GRADIENTER THIS attachment is a modification of the tangent screw attached to the horizontal axis of the tele- scope, and is used in measuring small vertical angles in terms of their tangents. It is useful in measuring distances, establishing grades, and similar work. It consists of a screw accurately cut to a determined number of threads which, passing through an eccentric sleeve nut on one side of the arm, presses against the small stud, A, fixed to the inside of the right-hand stand- ard. A drum having a rim of sterling silver is adjust- ably centered on the micrometer screw. This drum is graduated into 100 equal parts and a short arm carries a small scale, graduated to read complete turns of the micrometer screw, which serves as an index to the mi- crometer drum. Pressing against the opposite side of the stud is an enclosed spiral spring which maintains a positive movement of the Gradienter screw. USE OF THE GRADIENTER The Gradienter can be used for the determination of vertical angles less than 6 from the horizontal and also for the determination of horizontal distances, with- out reading the vernier on the vertical circle. DETERMINING DIFFERENCES IN ELEVATION. The initial reading for each determination should be taken when the graduated edge of the drum is near the zero mark on the index bar. For a depression angle, the center cross-hair of the telescope is placed on the H.. I. point of the rod and the reading of the micrometer is noted, using the nearest 98 W. & L. E. GURLEY, TROY, NEW YORK even division for general work and nearest one half division for close work. (The reading need not be zero, but may be any number from .to 100.) The micrometer is then turned until the instrument is level, the whole turns of the drum (each equal to 100 divisions) being counted or noted on the scale as the screw is revolved. When the level bubble is centered, the read- ing of the micrometer is noted, and the difference between the two readings, plus 100 for each whole turn of the screw determines the angle. For example, if the initial reading is 20 and is followed by two turns of the screw and a final reading of 32, the angle is equal to 212 divisions. As the screw is so cut that one com- plete turn intercepts one foot on a rod held 100 feet away, the difference in elevation is 2.12, times the dis- tance divided by 100. As the distances are measured from the center of the instrument there is no stadia constant. For an angle of elevation the procedure is the same, except that the instrument is first leveled, the initial reading on the micrometer taken, and the telescope is then turned upward to the H. I. point on the rod. DISTANCE MEASUREMENTS. Under ordinary condi- tions, for shots up to 1500 feet in length, the usual method of reading the stadia interval on the rod will probably be preferred but for the occasional long shots that are unavoidable in a traverse, and for work in hazy weather, the gradienter determination of distance is much more accurate and is easier to read. TRANSIT INSTRUMENTS 99 To determine the distance, the zero of the microm- eter drum is set opposite a division of the scale. Using the center cross-wire set the target near the bottom of a rod held on the point, the distance to which is desired. Read the target setting. Rotate the drum one complete turn and again set the target. Read the second target setting. The number of hundredths of a foot difference between the two target settings will be the distance in feet. As it is desirable to read as great an intercept on the rod as possible, it is sometimes necessary to read more than one complete turn of the micrometer screw. In general the distance equals the rod intercept in feet divided by the number of turns of the micrometer drum, the quotient multiplied by one hundred. For example : Drum reading 2.85 Rod reading 0.246 Drum reading 4.63 Rod reading 13.128 Turn of Drum = 1.78 Rod intercept 12.882 1 o CCO Distance = ^ - x 100 = 723.7 feet. 1 . I o Where this measurement is made on a heavy slope, the correct horizontal distance is obtained by using stadia i eduction methods. The original setting of the drum should be such that the screw can be rotated in a right hand direction. ESTABLISHING GRADES. One of the most important uses of the Gradienter is in establishing grades in sur- veying connected with railroads, streets, highways, sewers, canals, irrigation ditches, etc. The procedure is as follows: First, level the instrument: Bring the 100 W. & L. E. GURLEY, TROY, NEW YORK telescope level to its center by the clamp and the grad- ienter screws ; keeping the telescope level, the graduated head may be turned on its shaft until its zero is brought to the edge of the scale; then turn off as many spaces on the head as there are hundredths of feet to the hun- dred in the grade to be established. To avoid the possibility of error, observations should be taken by turning the screw always in the clock wise direction for the same series of observations. The Gradienter drum and the index are graduated on sterling silver ; thus the graduations are even,' distinct and permanent. The entire attachment is of such con- struction and workmanship that it can be depended upon for accurate work. See illustrations of Transit No. 10- A, Fig. 11, and Transit No. 10-A-3, Fig. 14. ADJUSTMENT OF THE GRADIENTER In the Gurley Gradienter attachment the value of the screw thread is such that a complete revolution of the screw will move the horizontal cross wire of the telescope over a space of one foot on a rod held at a distance of 100 feet. If the screw is turned through fifty spaces on its graduated head, the wire will pass over fifty one-hundredths, or one-half foot on the rod, and so on in the same proportion. The same ratio applies to metric measurements, 1 meter to 100 meters. If this condition does not obtain, loosen the hexa- gonal nuts and turn the eccentric to the right or left thus lengthening or shortening the arm until the ratio is as required. TRANSIT INSTRUMENTS 101 FIG. 29 Nos. 160 AND 161 DETACHABLE SIDE AND RIDING TELE- SCOPES, FOR VERTICAL SIGHTING IN MlNE SURVEYING 1 0-2. .W. & L. E. GURLEY, TROY, NEW YORK DETACHABLE TELESCOPES FOR VERTICAL SIGHTING IN MINE SURVEYING A convenient arrangement for sighting up or down a vertical shaft is shown in No. 160, in which an extra telescope is fitted with a flange and disk con- necting it with the axis, so as to make it precisely parallel with the main telescope. A counterpoise, as shown, is fitted to the other end of the axis, and both telescope and counterpoise can be detached and placed in the transit box when not in use. In No. 161, the extra telescope is connected with the main telescope by coupling nuts, which fasten it directly over the center of the instrument and allow its ready removal and replacement without disturbing its adjust- ments. In both arrangements the extra telescope is adjusted to the main telescope of the transit so that the lines of collimation of both are parallel and in the same plane, horizontal in No. 160 and vertical in No. 161; and in both, the extra telescope swings over the outside of the transit plates. The diagonal prism, No. 168, is often used with the extra telescope for greater conven- ience in sighting. REFLECTORS FOR ILLUMINATING CROSS WIRES. Nos. 165 and 166, are elliptical pieces of silver inclined at an angle of forty-five degrees with the ring, which is fitted to the objective end of the telescope. The opening of the reflector allows the use of the telescope, while a light held near the inner surface illuminates the cross wires. No. 165 is for transits and No. 166 is for levels. TRANSIT INSTRUMENTS 103 FIG. 30 NOS. 165 AND 166 CROSS WIRE ILLUMINATING REFLECTORS THE DIAGONAL PRISM, No. 168, is used when it is necessary to observe greater vertical angles than can be taken with the ordinary telescope. It consists of a prism attached to the cap of the eyepiece by means of which the image of the object is reflect- ed through a right angle to the eye. When the telescope is di- rected to the sun, a slide containing colored glass is moved over the opening to eliminate the glare. FIG. 31 NO. 168 DIAGONAL PRISM 104 W. & L. E. GURLEY, TROY, NEW YORK The circular plate to which the prism is attached is made to turn in the cap, so that, when it is substituted for the ordinary cap of the eyepiece, the opening of the prism can be easily adjusted to the position of the eye. Observations can be taken with the prism up to an angle of sixty degrees ele- vation. THE PLUMMET LAMP, No. 170, is a large plummet, of which the upper part is hol- low to contain oil. It has a tube with a wick, and an extinguisher. It is hung in gimbals by chains with a hook, and so always assumes a vertical position, and when suspend- ed from the shifting center of a leveling head it can be easily adjusted over a given point. These lamps are packed in a wooden case, furnished with a strap to sling over the shoulders. The weight of each lamp is about one and one-quarter pounds, and either one, two, or three may be packed in a single box. FIG. 32 170 PLUMMET LAMP TRANSIT INSTRUMENTS 105 PATENTED LATITUDE LEVEL, No. 193, is used for recovering the latitude on a solar transit without referr- ing to the vertical arc, and also for setting the telescope at any desired angle in running grades and similar work. It consists of a level connected by a short conical socket with the end of the telescope axis, to which it is clamped by a milled head screw, and made adjustable by a tangent screw and spring on the enlarged end of the tube. When the clamp screw is released the level turns vertically upon the axis, and can thus be set at any angle with the telescope, the final adjustment being made by its tangent screw. The latitude being set off upon the vertical arc as usual, the level is clamped and brought into the middle, as above described. The telescope may then be released and used in running lines, until it is desired to recover the latitude again. This is easily and accurately done without re- ferring to the vertical arc. The use of the attachment in running any desired grade is readily understood. Patented latitude level, No. 193, together with an ad- justing level, No. 196, and an adjusting bar, No. 197, are furnished without extra charge with any new transit having a Burt Solar Attachment. 106 W. & L. E. GURLEY, TROY, NEW YORK FIG. 33 No. 180 ATTACHED MAGNIFIER ATTACHED MAGNIFIERS OR MICROSCOPES are frequently used over the verniers of the horizontal or vertical limb, and are held by a universal three- jointed arm, which allows the lens to be placed over any point of the vernier. The magnifier for the "A" vernier can also be used for reading the vernier of the vertical limb (any style having one vernier.) Attached microscopes, Nos. 181 and 182, can be supplied if desired. See No. 18-A Piecise Transit, page 49. FIG. 34 No. 192 SOLAR SCREEN SOLAR SCREEN. If desired, we furnish a Solar Screen arranged to clamp to the eyepiece end of the telescope, and detachable at will. On this screen the image of the sun and cross wires can be readily observed, a greater focusing movement of the eyepiece, however, being required. TRANSIT INSTRUMENTS 107 ASTRONOMICAL TERMS IN the following pages we define the terms employed in the use and adjustment of the Solar Attachment, which may be helpful to one not familiar with solar instruments. (See Fig. 35). SUN. The sun is the fixed center of the solar sys- tem, although for convenience it is often spoken of as in motion around the earth. EARTH. The earth makes a complete revolution around the sun in three hundred and sixty-five days, five hours, forty-eight minutes, and forty-six seconds. It also rotates about an imaginary line passing through its center, termed its axis, once in twenty-three hours, fifty-six minutes, and four seconds, mean time, turning from west to east. POLES. The poles are the extremities of the axis. That in our hemisphere, known as the north pole, if produced indefinitely toward the heavens, would reach a point near the polar star, called the north pole of the heavens. EQUATOR. The equator is an imaginary line passing around the earth, equidistant from the poles, and in a plane at right angles with the axis. If the plane of the equator were produced to the heavens, it would form what is called the celestial equator. ORBIT. The orbit of the earth is the path in which it moves in its yearly revolution. If the plane of this orbit were produced to the heavens, it would form the ecliptic, or the sun's apparent path in the heavens. 108 W. & L. E. GURLEY, TROY, NEW YORK The earth's axis is inclined to its orbit at an angle of about 23 27', making an angle of the same degree be- tween the earth's orbit and its equator or between the celestial equator and the ecliptic. EQUINOXES. The equinoxes are the two points at which the ecliptic and the celestial equator intersect one another. DECLINATION OF THE SUN. The declination of the sun is its angular distance north or south of the celestial equator. When the sun is at the equinoxes, about the 21st of March and the 21st of September of each year, its declination is 0, or it is said to be on the equator. From these points its declination gradually increases, until on the 21st of June and the 21st of December it is 23 27' distant from the equator. It is the declination which causes the sun to appear so much higher in summer than in winter, its altitude in the heavens being about 46 54/ more on the 21st of June than it is on the 21st of December. HORIZON. The horizon of a place is the visible boundary of a plane, tangent to the earth at that place, or at right angles to a vertical line. The horizon, or a horizontal surface, is determined by the surface of a liquid at rest, or by the spirit levels of an instrument. ZENITH. The zenith of a place is the point directly overhead, in a line at right angles with the horizon. MERIDIAN. The meridian circle of a place is a great circle passing through the zenith of that place and the poles of the earth. TRANSIT INSTRUMENTS 109 The meridian, or true north and south line, is the line determined by the intersection of the plane of the meridian circle with the plane of the horizon. MERIDIAN ALTITUDE. The meridian altitude of the sun is its angular elevation above the horizon when passing the meridian of the place, and is equal to the co-latitude plus the declination. LATITUDE. The latitude of a place is its angular distance north or south of the equator, measured on the meridian. At the equator the latitude is 0, and at the poles 90. The co-latitude of a place is its angular dis- tance from the nearest pole, and is equal to 90 minus the latitude. LONGITUDE. The longitude of a place is its angular distance east or west of a given place taken as the starting point, or first meridian. It is measured on the equator or on any parallel of latitude. In the Nautical Almanac, which is commonly used with a solar instrument, the longitude of the principal places in the United States is reckoned from Greenwich, England, and expressed both in degrees and hours. ZENITH DISTANCE. The zenith distance of any heavenly body is its angular distance north or south of the zenith of a place, measured when the body is on the meridian. The zenith distance of the north pole is equal to the co-latitude. Suppose a person to be on the equator at the time of an equinox; the sun, when on the meridian, would be in the zenith of the place, and the poles of the earth would lie in a horizontal line. 110 W. & L. E. GURLEY, TROY, NEW YORK Disregarding, for the present, the declination of the sun, let us suppose that the person travels toward the north pole. As he passes to the north, the sun will descend from the zenith, and the pole will rise from the horizon in the same proportion, until when he arrives at the north pole of the earth the sun will have declined to the horizon, and the pole of the heavens will have reached the zenith. The altitude of the pole at any place, or the distance of the sun from the zenith, would, in the case supposed, give the observer the latitude of that place. If we now take into account the sun's declination, it will increase or diminish its meridian altitude, according as it passes north or south of the equator ; but the declin- ation of the sun at any time being known, its zenith distance, and therefore the latitude of the place, can be readily ascertained by an observation made when the sun is on the meridian. It is by this method that we obtain the latitude of any place by the Solar Attach- ment. TIME. A solar day is the interval of time between the departure of the sun from the meridian of a place and its succeeding return to the same position. The length of the solar day, by reason of the inclination of the earth's axis, is constantly changing. MEAN SOLAR DAY. In order to have a uniform measure of time, we have recourse to what is termed a mean solar day, the length of which is equal to the mean or average of all the solar days in a year. TRANSIT INSTRUMENTS 111 MEAN SOLAR TIME. The time thus given is called mean solar time, and is the same at any instant for all points on the same meridian, differing, however, at points on different meridians. STANDARD TIME. Since November, 1883, in the United States, the mean solar times of the meridians 60, 75, 90, and 120 west of Greenwich are adopted as standard time, and are called respectively Colonial, Eastern, Central, Mountain, and Pacific time. The time of each place differs from that of the next by one hour. Instead of employing the local mean solar time, the time used is the mean solar time at the nearest of the standard meridians. At Troy, N. Y., the longitude is 73 40' west, or four hours, fifty-four minutes and forty seconds; hence the mean solar time is five minutes and twenty seconds more than the standard time. At Minneapolis the long- itude is six hours, twelve minutes and fifty-seven seconds; hence the mean solar time is twelve minutes and fifty-seven seconds less than standard time, since the city is west of the meridian. EQUATION OF TIME. The sun is sometimes faster and sometimes slower than the clock, the difference being called the equation of time. It gives the difference between the solar day and the mean solar day. APPARENT NOON. The moment when the sun is on the meridian of any place is called apparent noon, and this being ascertained, we can, by adding the equation of time for the given day to, or subtracting it from, apparent noon, according as the sun is slow or fast, 112 W. & L. E. GURLEY, TROY, NEW YORK obtain the time of mean noon, which, converted to stan- dard time, is used to set the watch. DIFFERENCE OF LONGITUDE. As the earth makes a complete rotation upon its axis once a day, every point on its surface must pass through three hundred and sixty degrees in twenty-four hours, or fifteen degrees in one hour, and so on in the same ratio. As the rotation is west to east, the sun would come to the meridian of every place fifteen degrees west of Greenwich just one hour later than the time given in the Ephemeris for apparent noon at Greenwich. To an observer at Troy, N. Y., the longitude of which is, in time, four hours, fifty-four minutes, forty seconds, the sun would come to the meridian nearly five hours later than at Greenwich, and thus, when it is 12 M. at that place it is only about 7 A. M. in Troy. REFRACTION. By reason of the atmosphere, the rays of light from the sun are bent out of their course, so as to make its altitude appear greater than is actually the case. The refraction varies according to the altitude of the body observed, being zero when it is in the zenith, about one minute when midway from the zenith to the horizon, and almost thirty-four minutes when in the horizon. The proper allowance to be made for refraction in setting off the declination is fully explained on pages 125 to 131. EFFECT OF REFRACTION. If the latitude and decim- ation of the sun were both zero, the position of the sun at noon would be at the zenith and there would be no TRANSIT INSTRUMENTS 113 refraction. At any other latitude, declination or hour, the apparent position of the sun would be lower and refraction must be taken into account. Again, the angles which the equatorial lines of the Solar Attachments make with the horizontal are con- tinually changing, as the declination arm is made to follow the course of the sun during an entire day. Thus in the morning and evening the equatorial lines are more or less inclined to the horizon, while at noon they are parallel with it. It follows that the excess of refraction at morning and evening is in some measure balanced by the fact that the position of the sun's image with refer- ence to the equatorial lines is then less affected by it, on account of the greater inclination of the lines to the horizon. 114 W. & L. E. GURLEY, TROY, NEW YORK BURT SOLAR ATTACHMENT THE solar attachment is essentially the solar appara- tus of William A. Burt, placed upon the cross bar of the ordinary transit. A disk one and one-half inches in diameter, having a short, round pivot project- ing above its upper surface, is screwed to the telescope axis. Upon this pivot rests the enlarged base of the polar axis, which is firmly connected with the disk by four capstan head screws passing from the under side of the disk into the base. These screws serve to adjust the polar axis, as will be explained hereinafter. HOUR CIRCLE. The hour circle surrounding the base of the polar axis is easily movable about it, and can be fastened at any point desired by two flat head screws above. It is graduated to five minutes of time, is figured from I to XII, and is read by an index fixed to the dec- lination arc and moving with it. A hollow cone or socket, fitting the polar axis and made to move upon it, or to be clamped at any point desired by a milled head screw on top, furnishes by its arms below a firm sup- port for the declination arc, which is fastened to it. DECLINATION ARC. The declination arc has a radius of five inches, is graduated to quarter degrees, and reads by vernier to single minutes. The declination arc has the usual lenses and silver plate on the two opposite blocks, also a clamp and tangent movement, as shown in the illustration. The arc of the declination limb is turned on its axis and one or the other solar lens is used, as the sun is north or south of the equator. The illus- tration shows its position when the sun is north. TRANSIT INSTRUMENTS 115 LATITUDE ARC. The latitude is set off by means of a large vertical limb figured from the center each way in two rows, from to 80 degrees and from 90 to 10 degrees, the first series being intended for reading ver- tical angles, and the second series for setting off the FIG. 35 No. 190 BURT SOLAR ATTACHMENT latitude. The vernier of the vertical limb is made movable by the tangent screw so attached that its zero and that of the limb are readily made to coincide when, in adjusting the limb to the level of the telescope, the arc is clamped to the axis. 116 W. & L. E. GURLEY, TROY, NEW YORK The usual tangent movement to the telescope axis serves to incline the telescope to the proper angle, as described. A level on the under side of the telescope, with ground and graduated vial is indispensable in the use of the solar attachment. The arcs, verniers, and hour circle are all graduated on sterling silver. EXPLANATION OF THE BURT SOLAR ATTACHMENT. When the telescope is set horizontal by its spirit level, the hour circle will be in the plane of the horizon, (see Fig. 36), the polar axis will point to the zenith, and the zeros of the vertical arc and its vernier will coincide. If we incline the telescope, directed north, the polar axis will descend from the direction of the zenith. The sun's polar distance, or the co-latitude of the place, can be laid off on the vertical arc the latitude itself being found by subtracting this amount from 90 degrees, or by reading the inner row of figures, which amounts to the same thing. When the sun passes above or below the equator, its declination, or angular distance from it, as given in the Ephemeris, can be set off upon the declination arc, and its image brought into position as before. In order to do this, however, it is necessary not only that the latitude and declination be correctly set off upon their respective arcs, but also that the instrument be moved in azimuth until the polar axis points to the pole of the heavens, or, in other words, is placed in the plane of the meridian. Thus the position of the sun's image will indicate not only the latitude of the place, the dec- lination of the sun for the given hour, and the apparent TRANSIT INSTRUMENTS 117 time, but it will also determine the meridian, or true north and south line passing through the place where the observation is made. The interval between two equa- torial lines, as well as between the hour lines on the silvered blocks, is just sufficient to include the circular image of the sun, as formed by the solar lens on the opposite end of the revolving arm. DECLINATION. Allowance for declination: Let us now suppose the observation made when the sun has passed the equinoctial point, and when its position is affected by declination. By referring to the Ephemeris, and setting off on the arc the declination for the given day and hour, we are still able to determine its position with the same certainty as if it remained on the equator. When the solar attachment is accurately adjusted and the transit plates precisely horizontal, the latitude of the place and the declination of the sun for the given day and hour being set off on their respective arcs, and the instrument set approximately north by the magnetic needle, the image of the sun cannot be brought between the equatorial lines until the polar axis is placed in the plane of the meridian of the place, or in a position par- allel with the axis of the earth. The slightest deviation from this position will cause the image to pass above or below the lines, and thus the error will be detected. From the position of the sun in the solar system we thus obtain a direction absolutely unchangeable, from which to run lines and measure horizontal angles. 118 W. & L. E. GURLEY, TROY, NEW YORK This simple principle is not only the basis of the construction of solar instruments, but it is the sole cause of their superiority over instruments having only the magnetic needle. For in an instrument having a mag- netic needle, the accuracy of the horizontal angles indicated, and therefore of all the observations made, depends upon the delicacy of the needle and the con- stancy with which it assumes a certain direction, called the magnetic meridian. ADVANTAGES OF THE BURT SOLAR ATTACHMENT. The attachment can be added to the telescope of any good transit at a comparatively small expense, thus enabling the surveyor to establish the true meridian, to determine the correct latitude, and to obtain true time approximately. Its adaptation to the purposes of illustration and instruction in practical astronomy in colleges and schools will occur to every teacher; and it furnishes for the surveyor a long sought and much needed instrument. When not in use the attachment should be removed from the telescope and packed in the instrument box, and the thin shield put on the polar axis and kept in its place by the screw and washer of the socket. It is evident that all transits to which the solar attachment is to be added should have a horizontal limb and verniers, and should be furnished with a level on telescope, clamp and tangent to telescope axis, and a vertical arc and vernier. They should also have a mov- able compass circle to set off the magnetic declination, and should be leveled by leveling screws. They must TRANSIT INSTRUMENTS 119 FIG. 36 No. 30-A PRECISE TRANSIT WITH BURT SOLAR ATTACHMENT ILLUSTRATION ALSO SHOWS BEAMAN STADIA ARC 120 W. & L. E. GURLEY, TROY, NEW YORK be in perfect order, especially in respect to the sockets, before correct work can be done. CARE OF THE BURT SOLAR ATTACHMENT. The Solar Attachment can be used with satisfactory results only on a transit which is in good repair and adjustment. The errors arising from defects either in worn or dam- aged bearings or imperfect adjustment have a direct effect on the Solar Attachment. The principal sources of error in the transit are found in damaged plates or centers, loose centers, or irregular or loose bearings of the telescopic axis. The latter is the most frequent, and effects the setting of the latitude by describing an elipse instead of a true arc. The transit must be kept clean at all times, the polar axis covered with the shield provided for the purpose when the Solar is not in use, and the tapered bearing and seat, as well as the socket of the Attachment, thoroughly cleaned with a soft cloth before using. By taking the precautions mentioned and barring accidents, the Solar will remain in perfect order and adjustment indefinitely. To ADJUST THE BURT SOLAR ATTACHMENT To adjust the Burt Solar Attachment, proceed as follows : ._ SOLAR LENSES AND LINES. Detach the declination arm by taking off the clamp and tangent screws, and remove the center by which the arm is pivoted on the arc. Substitute for the declination arm upon the attach- ment the adjusting bar furnished with every solar TRANSIT INSTRUMENTS 121 instrument. The center of the declination arm fitting into the hole at one end of the bar, and the bar being further secured to the attachment by the clamp screw passing through the hole in the declination arc left by the removal of the tangent screw, into the threaded hole at the other end of the adjusting bar, thus forms a sup- port upon which the declination arm can be adjusted. Place the declination arm on the adjuster, turn one end to the sun, and bring it into such a position that the image of the sun is made to appear precisely between the equatorial lines on the opposite plate. Carefully turn the arm over, until it rests upon the adjuster by the opposite faces of the rectangular blocks, and again observe the sun's image. If it remains be- tween the lines as before, the arm is in adjustment. If not, loosen the three small screws and move the silver plate under their heads until one half the error in the position of the sun's image is removed. Bring the image again between the lines, and repeat the operation as above on both ends of the arm, until the image will remain between the lines of the plate in both positions of the arm, when it will be in proper adjust- ment, and the arm may be replaced in its former position on the attachment. This adjustment is very rarely needed in our instruments, the lenses being cemented in their cells and the plates securely fastened. To ADJUST THE VERNIER OF THE DECLINATION ARC. Set the vernier at zero, and raise or lower the telescope until the sun's image appears exactly between the equatorial lines. 122 W. & L. E. GURLEY, TROY, NEW YORK Having the telescope axis clamped, carefully revolve the arm until the image appears on the other plate. If precisely between the lines, the adjustment is complete. If not, move the declination arm by its tangent screw until the image w r ill come precisely between the lines on the two opposite plates. Clamp the arm and remove the index error by loosening two screws that fasten the ver- nier; place the zeros of the vernier and limb in exact coincidence, tighten the screws, and the adjustment is complete. To ADJUST THE POLAR Axis. Level the instrument carefully by the long level of the telescope, using the tangent movement of the telescope axis in connection with the leveling screws, until the bubble will remain in the middle during a complete revolution of the instru- ment upon its axis. Place the solar attachment upon the axis and see that it moves easily around it. Bring the declination arm into the same vertical plane with the telescope, place the Adjusting Level, No. 196, upon the top of the rectangular blocks, and bring the bubble of the level into the middle by the tangent screw of the declination arc. TRANSIT INSTRUMENTS 123 FIG. 37 No. 196 STRIDING OR ADJUSTING LEVEL Turn the arc half way around, bringing it again parallel with the telescope, and note the position of the level. If in the middle, the polar axis is vertical in that direction. If not in the middle, correct one half the error by the capstan head adjusting screws under the base of the polar axis, moving each screw of the pair the same amount, but in an opposite direction. Bring the level to the middle again by the tangent screw of the declination arc, and repeat the operation as before, until the bubble will remain in the middle when the adjusting level is reversed. 124 W. & L. E. GURLEY, TROY, NEW YORK Pursue the same course in adjusting the arc in the second position, or over the telescope axis, and when completed the level will remain in the middle during an entire revolution of the arc, showing that the polar axis is at right angles with the level under the telescope, or truly vertical. As this is by far the most delicate and important adjustment of the solar attachment, it should be made with the greatest care, the bubble being kept precisely in the middle and frequently inspected Li the course of the adjustment. The adjusting level itself can be easily corrected, if necessary, by the screw at one end, when reversed upon a plane surface, exactly as a mason's level is adjusted. To ADJUST THE HOUR ARC. Whenever the instru- ment is set in the meridian, as will be hereafter describ- ed, the index of the hour arc should read apparent time. If not, loosen the two flat head screws on the top of the hour circle, and with the hand turn the circle around until the proper reading is indicated, fasten the screws again, and the adjustment will be complete. To USE THE BURT SOLAR ATTACHMENT 1. Compute the sun's declination for the day and the hours when observations are to be made, as shown in the examples on pages 132 to 134. 2. Set the declination arc for the hour as computed. 3. Carefully level the transit, using the long tele- scope level for precision. TRANSIT INSTRUMENTS 125 4. Set the latitude of the place on the vertical circle or arc, and the zeros of the horizontal limb and south vernier in coincidence. All motions are now clamped. Release the lower socket motion and turn the transit until the sun's image is precisely between the horizontal lines, using the lower tangent screw. The instrument will then be in the true meridian, and an angle read by the verniers is the angle from the meridian. NOTE 1. During north declination, or between the months of March and September, the graduated arc end of the Solar Attachment is pointed toward the sun. During the other one-half of the year, the opposite end is toward the sun. NOTE 2. The greater the care exercised in setting the declination and latitude and the leveling of the instrument, the better will be the results obtained. Observations may be made with the telescope pointed north, objective end depressed; again with the telescope pointed south, eye end depressed; or again with the telescope reversed and the attachment on the other side two other observations. Thus with four distinct observations, the mean may be taken and any errors of adjustment eliminated. REFRACTION IN DECLINATION. The Table of Re- fractions on pages 127 to 131 is calculated for latitudes between 2l/ 2 and 70, at intervals of 2l/ 2 , that being as near as is required. The declination ranges from to 20 both north and south, the -|- declinations being north and the 126 W. & L. E. GURLEY, TROY, NEW YORK south, and is given for every 5, that being sufficiently near for all practical purposes. The hour angle in the first column indicates the distance of the sun from the meridian in hours, the refraction given for hours being that which affects the observed declination of the sun when on the meridian, commonly known as meridional refraction. The refraction for the hour just before or after noon is so nearly that of the meridian that it may be called and allowed as the same. When the table is used, it must be remembered that when the declination is north the algebraic sign in the table is plus, when it is south the algebraic sign is minus, and the declination is always added algebraically. It will be noticed that the refraction in south, or , declination increases very rapidly as the sun nears the horizon, showing that observations should not be taken with the sun when it is south of the equator, less than one hour from the horizon. THE SOLAR EPHEMERIS is published annually. It is an abridgment of the Nautical Almanac, issued by the United States Government, and contains a Table of Mean Refractions in Declination and Tables of Times of Elongation, Culmination and Azimuths of Polaris. It can be conveniently carried in the vest pocket. A copy will be sent postpaid to any engineer or surveyor, upon request. TRANSIT INSTRUMENTS 127 TABLE OF MEAN REFRACTIONS IN DECLINATION To apply on the declination arc of the Solar Attach- ment of either compasses or transits. Computed by Edward W. Arms, C. E., for W. & L. E. Gurley, Troy, N. Y. DECLINATIONS 11 For Latitude 2 30' +20 +15- +10 +5 5 10 15 20 h. 18" 12" 07" 02" +02" 07" 12" 18" 23" 2 18 12 07 02 +02 07 12 18 23 3 17 11 06 01 +03 08 13 19 25 4 15 10 05 +05 10 15 21 27 5 10 05 +05 10 15 20 26 32 For Latitude 5" h. 15" 10" 05" 0" +05" 10" 15" 20" 27" 2 15 10 05 +05 10 15 20 27 3 13 08 03 +02 07 12 17 23 29 4 10 05 +05 10 15 20 27 32 5 05 +05 10 15 20 27 32 40 For Latitude 7 30' h. 13" 08" 02" +02" 08" 13" 18" 24" 29" 2 12 07 01 +03 09 14 19 25 31 3 10 05 +06 10 15 20 26 32 4 05 +05 10 15 20 26 32 39 5 +07 12 17 23 29 36 43 51 I'Ol For Latitude 10 h. 10" 05" 0" +05" 10" 15" 20" 26" 32" 07 03 +02 07 12 17 22 28 34 3 05 +03 08 13 19 25 31 38 4 05 10 15 20 26 32 39 46 5 + 15 20 26 32 39 46 55 1'06 1'19 For Latitude 12 30' h. 08" 02" +02" 08" 13" 18" 24" 30" 36" 2 06 00 +05 10 15 20 26 32 39 3 +02 07 12 17 23 29 36 43 51 4 ' 04 09 14 20 25 31 40 48 55 5 21 27 33 40 48 57 1'08 1'23 1'41 128 W. & L. E. GURLEY, TROY, NEW YORK TABLE OF MEAN REFRACTIONS IN DECLINATION HOUR ANGLE DECLINATIONS For Latitude 15 +20 +15 + 10 +5 5 10 15 20 h. 2 3 4 5 05" 03 +01 08 29 0" +02 05 12 34 +05" 07 11 19 41 10" 12 16 24 49 15" 18 22 30 59 21" 23 28 37 no 27" 29 34 44 1'24 33" 36 41 53 1'43 40" 43 49 1'04 208 For Latitude 17 30' h. 02" +02" 08" 13" 18" 24" 30" 36" 44" 2 05 10 15 21 27 33 40 48 3 +02 10 15 21 27 33 40 48 57 4 13 18 23 29 35 43 51 I'Ol 1'13 5 34 41 49 58 no 1'23 1'41 206 242 For Latitude h. 0" 05" 10" 15" 21" 27" 33" 40" 48" 2 03 07 13 18 24 30 36 44 52 3 06 13 18 24 30 36 44 52 1'02 4 17 22 28 35 42 50 I'OO I'll 126 5 39 47 57 1'07 1'20 1'37 200 232 325 For Latitude 22 30' h. C2" 08" 13" 18" 24" 30" 36" 44" 52" 2 06 11 15 21 27 33 40 48 57 3 11 15 21 27 33 40 48 57 1'OS 4 20 26 32 39 46 56 1'07 1'19 137 5 45 53 1'03 1'16 1'31 1'52 221 307 428 For Latitude 25 h. 05" 10" 15" 21" 27" 33" 40" 48" 57" 2 08 14 19 25 31 38 46 54 1'05 3 12 18 24 30 37 44 53 1'04 118 4 23 29 35 45 53 1'03 1'16 131 152 5 49 59 no 1'24 1'42 2 07 244 346 543 For Latitude 27 30' h. 08" 13" 18" 24" 3' " 36" 44" 52" 1'02" 2 11 16 22 28 3-i 41 49 I'OO 1 10 3 17 28 35 42 50 I'OO 1 11 126 4 28 35 42 50 I'OO I'll 126 143 209 5 54 1'05 1'18 1'34 154 224 311 438 815 For Latitude 30 h. 10" 15" 21" 27" 33" 40" 48" 57" 1'OS" 2 14 19 25 31 38 46 54 I'Oo 1 18 3 20 26 32 39 47 55 I'OO 1 19 136 4 32 39 46 52 roe 1'19 135 157 229 5 I'OO no 1'24 1'42 207 244 346 543 1306 TRANSIT INSTRUMENTS 129 TABLE OF MEAN REFRACTIONS IN DECLINATION *3 DC ox W <* DECLINATIONS For Latitude 32 30' +20 +15 +10 +5 5 10 15 20 1'14" 126 147 254 h. 3 4 5 13" 17 23 35 1'03 18" 22 29 43 1'15 24" 28 35 51 1'31 30" 35 43 I'Ol 1 53 36" 42 51 1'13 220 44" 50 I'Ol 127 305 52" I'OO 113 146 4 25 1'02" 1 11 128 213 736 For Latitude 35 c h. 15" 21" 27" 33" 40" 48" 57" 1'08" 1-21" 2 20 25 32 38 46 55 1'05 118 1 35 3 26 33 39 47 56 1'07 121 138 2 00 4 39 47 56 1'07 1'20 136 159 232 325 :> 1'07 1'20 1'38 200 234 329 5 14 1016 For Latitude 37 c h. 18" 24" 30" 36" 44" 52" 1'02" 1'14" 1'29" 2 22 28 35 42 50 I'OO 112 126 145 3 29 36 43 52 1'02 114 129 149 216 4 43 51 I'Ol 1'13 127 149 214 254 405 5 I'll 1'26 144 210 249 355 6 15 14 58 For Latitude 40 C h. 21" 27" 33" 40" 48" 57" 1'08" 1'21" 1'39" 2 25 32 39 46 52 1'06 119 135 157 3 33 40 48 57 1'OS 121 138 202 236 4 47 55 1'06 1'19 1 36 158 230 321 459 5 1'15 1'31 151 220 305 425 734 25 18 For Latitude 42 30' h. 24" 30" 36" 44" 52" 1'02" 1'14" 1'29" 1'49" 2 28 35 39 50 I'OO 112 126 1 45 211 3 36 43 52 1'02 113 1 29 1 49 217 2 59 4 50 I'OO I'll 126 144 210 249 3 55 616 o 1'19 1 36 1 58 230 322 500 924 For Latitude 45 o h. 27" 33" 40" 48" 57" 1'08" 1'21" 1'39" 2 '02" 2 32 39 46 52 1'06 119 1 35 157 229 3 40 47 56 1'07 121 1 38 200 234 329 4 54 1'04 1'16 1 33 154 224 311 438 8 15 5 1'23 141 205 241 340 540 1202 For Latitude 47 30' h. 30" 36" 44" 52" 1'02" 1'14" 1'29" 1'49" 2'18" 2 ' 35 42 50 I'OO 112 126 1 45 201 2 51 3 43 51 I'Ol 113 128 1 47 2 15 256 408 4 56 1'09 123 1 40 2 05 240 339 5 37 11 18 5 1'27 1 46 2 12 2 52 401 030 16 19 130 W. & L. E. GURLEY, TROY, NEW YORK TABLE OF MEAN REFRACTIONS IN DECLINATION HOUR ANGLE DECLINATIONS For Latitude 50 +20 +15 +10 +5 5 10 1'39" 157 231 418 24 10 15 2'02" 228 323 659 20 h. 2 3 4 5 33" 38 47 1'02 130 40" 46 56 114 151 48" 55 1'06 129 219 57" 1'06 119 148 304 1'08" 118 136 216 422 1'21" 135 158 2 58 728 2'36" 319 502 1947 For Latitude 52 30' h. 36" 44" 52" 1'02" 1'14" 1'29" 1'49" 2 '18" 3'05" 2 43 50 59 111 126 142 223 249 355 3 50 I'OO I'll 126 145 211 251 358 622 4 1'05 1 18 135 2 10 228 319 453 842 5 134 156 227 3 16 447 852 For Latitude 55 h. 40" 48" 57" 1'08" 1'21" 1'39" 2'02" 2'36" 3'33" 2 46 55 1'05 118 1 34 156 230 315 447 3 55 1'06 1 19 135 158 230 321 4 44 919 4 no 123 142 206 243 344 549 12 41 5 137 201 234 328 515 1018 For Latitude 57 30' h. 44" 52" 1'02" 1'14" 1'29" 1'49" 2'18" 3'05" 4'37" 2 50 59 111 125 143 209 247 351 604 3 58 I'lO 124 1 42 207 243 345 550 1247 4 I'll 125 143 210 2 50 355 614 2024 5 1 41 206 242 342 546 1226 For Latitude 60 h. 48" 57" 1'08" 1'21" 1'39" 2'02" 2'36" 3'33" 5'23" 2 54 1'04 117 133 154 224 312 438 815 3 1'03 1 15 130 1 51 220 304 424 731 2444 4 1 18 1 34 156 228 3 18 450 853 5 145 211 250 357 621 1532 For Latitude 02 30' h. 2 52" 58 1'02" 1 09 1'14" 123 1'29" 141 1'50" 206 2'18" 243 3'00" 344 4'17" 550 7' 13" 1244 3 1'07 123 138 201 235 330 516 1024 4 1 23 140 205 240 340 537 1150 , 5 148 217 259 414 703 For Latitude 65 h. 57" 1'08" 1'21" 1'39" 2'02" 2'36* 3'33" 5'23" 10'51" 2 1'03 116 1 31 152 221 307 428 744 3 112 127 146 212 252 402 633 4 127 147 213 254 405 640 5 152 222 308 430 752 TRANSIT INSTRUMENTS 131 TABLE OF MEAN REFRACTIONS IN DECLINATION HOUR ANGLE DECLINATIONS For Latitude 67 30' +20 +15 +10 +5 5 10 4'17" 532 834 15 7'13" 1128 20 h. 2 3 4 5 1'02" 108 1 17 132 156 1'14" 122 134 153 228 1'29" 140 155 223 317 1'50" 203 226 314 440 2'18" 239 314 435 851 3'00" 337 444 805 For Latitude 70 e h. 1'08" 1'21" 1'39" 2'02" 2'36" 3'33" 5'23" 10'51" 2 114 129 1 50 218 300 417 713 3 123 143 205 241 341 559 1215 4 137 200 234 328 520 10 12 5 202 233 327 511 1005 132 W. & L. E. GURLEY, TROY, NEW YORK To COMPUTE THE DECLINATION OF THE SUN Suppose the corrected declination is desired for the different hours of May 15,, 1919, at Troy, N. Y. The latitude is 42 44-'. The longitude is practically five hours; so that the declination given in the Ephemeris for apparent noon of that day at Greenwich would be that for 7 A. M. at Troy, or five hours earlier. Note carefully the algebraic signs. The declination is North or plus. Its hourly difference is plus. The refraction always is plus. Hence we use the algebraic sum: +18 40' 44". 3 is the tabular decimation for 7 A. M. +36". difference for one hour +18 41' 20". 3 + ref. (4 hrs.) 55" 18 42' 15" 8 A. M. +36".0 +18 41' 56". 3 + ref. (3 hrs.) 39" = 18 42' 35" 9 A. M. +36".0 +18 42' 32". 3 + ref. (2 hrs.) 30" 18 43' 02" 10 A. M. +36".0 + 18 43' 08". 3 + ref. (1 hr. ) 26" = 18 43' 34" 11 A. M. +3G".0 +18 43' 44". 3 + ref. (0 hrs.) 26" = 18 44' 10" 12 Noon +36".0 +18" 44' 20". 3 + ref. (1 hr. ) 26 = 18 44' 46" 1 P. M. -f36".0 + 18 44' 50". 3 + ref. (2 hrs.) 30" = 18 45' 26" 2 P. M. + 36".0 4-18 45' 32". 3 + ref. (3 hrs.) 39" = 18 4G' 11" 3 P. M. +36".0 +18 46' 08". 3 4- ref. (4 tors.) 55" = 18 47' 03" 4 P. M. +36".0 +18 46' 44". 3 + ref. (5 hrs.) 1'2G" = 18 48' 10" 5 P. M. TRANSIT INSTRUMENTS 133 Again, suppose the corrected declination is desired for the different hours of October 20th, 1921, at Troy, N. Y. Now the declination and hourly difference are. both minus and the refraction is plus. 10 03' 29". 2 the tabular declination for 7 A. M. 54". 2 difference for one hour 10 04' 23". 4 + ref. (4 hrs.) 2'49" 10 01' 34" 8 A. M. 54". 2 10 05' 17". 6 + ref. (3 hrs.) 1'49" 10 03' 29" 9 A. M. 54". 2 10 06' 11". 8 + ref. (2 hrs.) 1'26" = 10 04' 46" 10 A. M. 54". 2 10 07' 06". + ref. (1 hr. ) 1'14" 10 05' 52" 11 A. M. 54". 2 10 08' 00". 2 + ref. (0 hr. ) 1'14" = 10 06' 46" 12 Noon 54". 2 10 08' 54". 4 + ref. (1 hr. ) 1'14" = 10 07' 40" 1 P. M. 54". 2 10 09' 48". 6 + ref. (2 hrs.) 1'26" 10 08' 23" 2 P. M. 54". 2 10 10' 42". 8 + ref. (3 hrs.) 1'49" = 10 08' 54" 3 P. M. 54". 2 10 11' 37". + ref. (4 hrs.) 2'49" = 10 08' 48" 4 P. M. It will be found that the use of the table, as illus- trated above, will not only relieve the surveyor of the perplexity which hitherto attended the subject of refrac- tions, but will also enable him to secure more accurate results than by some other methods commonly given. 134 W. & L. E. GURLEY, TROY, NEW YORK The calculation of the declination for the different hours of the day should, of course, be made and noted before the surveyor begins his work, that he may lay off the change from hour to hour, from a table prepared as before described. To FIND THE LATITUDE Level the instrument very carefully, using the tele- scope level, until the bubble will remain in the middle during a complete revolution of the instrument, the tangent movement of the telescope being used in con- nection with the leveling screws, and the axis of the telescope being clamped. Clamp the vertical arc, so that its zero and the zero of its vernier coincide as near as may be, and bring them into exact line by the tangent screw of the vernier. Set off on the proper arc the declination of the sun for apparent noon of the given day, corrected for the meridional refraction. Note the equation of time, and fifteen or twenty minutes before noon direct the telescope to the north and lower the objective end until the sun's image can be brought nearly into position be- tween the equatorial lines, by moving the instrument upon its spindle and the declination arc from side to side. The declination arc being brought directly in line with the telescope, clamp the axis, and with the tangent screw of the telescope axis bring the image precisely between the lines, following the sun's motion as the image runs below the lower equatorial line, or, in other words, as long as the sun continues to rise in the heavens. TRANSIT INSTRUMENTS 135 When the sun reaches the meridian the image will remain stationary in altitude for an instant, and will then begin to rise on the plate. The moment the image ceases to run below is appar- ent noon, when the index of the hour arc should indicate XII, and the latitude be determined by the reading of the vertical arc. The angle through which the polar axis has moved in the operation just described is measured from the zenith instead of the horizon, so that the angle read on the vertical limb is the complement of the latitude, or is the co-latitude. The latitude itself is readily found by subtracting this angle from 90. Thus at Troy the reading of the limb being found as above directed to be 47 16', the latitude will be 90 47 16' = 42 44'. The latitude may also be read direct by referring to the inner row of figures on the arc, beginning with 90 in the middle and reading to 10 on either side. TIME FOR USING THE SOLAR While the solar attachment can be used with advan- tage at all seasons of the year, the most favorable time is the summer, when the declination is north and the days are long and more generally fair. It is best not to take the sun at morning and evening when it is within half an hour of the horizon, nor at noon for about the same interval before and after it passes the meridian. In favorable weather surveys can be made more rapidly than with the needle instrument, there being no 136 W. & L. E. GURLEY/TROY, NEW YORK time consumed in waiting for the needle to settle, or in avoiding the errors due to local attraction. When the sun is obscured the lines can be run by the needle alone, it being always kept with the sun, or at on its arc, thus indicating the direction of the true meridian. The sun, however, must be regarded as the most reliable guide, and should, if possible, be taken at every station. GURLEY TELESCOPIC SOLAR ATTACHMENT When a continued series of solar observations are to be made, it is often desirable that the main telescope of the transit be used without disturbing the solar appa- ratus. The new Gurley Telescopic Solar Attachment meets such requirement, as the main telescope of the transit may be used independently and solar observations taken with no change in settings other than the hourly change in declination. The instrument is so designed that its adjustments can be accomplished with ease and pre- cision in the field. As shown in the illustration on page 138, the sun is viewed through an auxiliary telescope, a reflector being placed in front of the objective that brings the sun's reflected image to the cross wires. The solar telescope is mounted on a horizontal axis which is supported by a vertical triangular base fastened to the right hand standard. The solar telescope can be moved about its horizontal axis and if the latitude is laid off on the latitude arc, the solar telescope will coin- cide with the polar axis. TRANSIT INSTRUMENTS 137 The declination arm tilts the mirror at the objective end of the solar telescope, the angle being read on the arc attached to its side. Both the latitude arc and the declination arm have clamp and tangent movements for convenience in setting. Having set the main telescope in the meridian and adjusted the mirror to the proper declination, the course of the sun is followed by rotating the solar telescope in collar bearings about its own axis; an hour circle sur- rounding the solar telescope indicates the apparent time. The Gurley Telescopic Solar adds but little weight and when furnished in connection with a Gurley Precise Mountain Transit, with One Piece Truss Standard, is the standard instrument for public land surveys and similar work requiring exceptionally accurate results. 138 W. & L. E. GURLEY, TROY, NEW YORK FIG. 38 No. 32-A PRECISE TRANSIT WITH TELESCOPIC SOLAR ATTACHMENT, U. S. GENERAL LAND OFFICE AND U. S. FOREST SERVICE MODEL TRANSIT INSTRUMENTS 139 To ADJUST THE GURLEY TELESCOPIC SOLAR ATTACHMENT TRANSIT ADJUSTMENT. Care should be taken to see that the main transit is adjusted for plate levels, col- limation and telescope level before attempting to adjust Solar. FOCUSING SOLAR. The eyepiece of the solar tele- scope is focused on the crosswires by rotating the knurled ring nearest the eye. The objective is focused by pulling out on the tube which holds the eyepiece. EQUATORIAL WIRES PARALLEL TO THE Axis OF THE REFLECTOR. Set for approximate latitude declination and hour angle, orient to approximate meridian and view the reflected image of the sun. Turn the telescope back and forth in hour angle, that is, in its collar bear- ings, and the image should follow the wires from side to side. If it does not, unscrew the cover ring just back of the knurled head, loosen the cross wire screws and turn the diaphragm. If sun is not visible any other well defined distant point may be used. COLLIMATION OF THE SoLAR TELESCOPE. Unclamp the vernier arm of the declination arc and swing the mirror parallel to the line of sight, thus giving a direct view through the auxiliary telescope. Sight on some distant point and revolve the telescope in its collar bear- ings 180 degrees, adjusting the cross wires as for the Wye Level. The first adjustment should always be checked after adjusting the collimation. POLAR Axis AT RIGHT ANGLES TO LATITUDE Axis. Transit on fore and back sights, the same as for collima- 140 W. & L. E. GURLEY, TROY, NEW YORK ting the main telescope. If any adjustment is necessary, make it by means of the three screws which are in the short arm on the upper end of the latitude arc. The middle screw pulls the eye end closer to the transit; the outside screws oppose the center screw and push the eye end farther away. LATITUDE Axis PARALLEL TO TRANSIT Axis. Care- fully level the transit and make the solar telescope cut the same line as the main telescope when sighted at some distant object. Make any necessary adjustment by means of the capstan nuts holding the lower corner of the triangular base to the standard. Make the auxiliary telescope trace the same vertical line as the main telescope, adjusting by means of the capstan nuts at the upper corner of the triangular base, if necessary. It will be necessary to alter the focus of the solar telescope to make this test. This test is similar to that for the adjustment of the standards of the main telescope. ZERO OF LATITUDE ARC. Level the main telescope and make both telescopes agree on a distant object. If the latitude vernier does not read zero, loosen the two screws at the back of the vernier and correct it. It is necessary that the main telescope level be adjusted parallel to the line of collimation. ZERO OF DECLINATION ARC. Turn the mirror back into position and set the declination arm to read zero. Through the auxiliary telescope observe the reflected image of some prominent and distant horizontal object. Reverse the telescope 011 the latitude axis and view the TRANSIT INSTRUMENTS 141 same object. If the wires do not cut the same point, make the adjustment for one half the error, by means of the two small abutting screws in the middle of the declination arm, operating against the short arm attached to the axis of the mirror. This may also be checked by a noon reading on the sun, other adjustments having been made. HOUR CIRCLE. When the instrument is pointed in the meridian, the hour circle should read apparent time. A screw in the rim of the hour circle on the side opposite the zero hour can be loosened and any necessary cor- rection made by turning the graduated circle to the proper position. DIRECT OBSERVATION ON THE SUN With a transit having both vertical and horizontal limbs, direct observations may be taken on the sun to find the meridian. The best time is about three hours before or after noon. A colored or smoked glass dark- ener will be necessary over the eyepiece to protect the eye. The observations to be taken are those of the alti- tude of the sun and its horizontal angle from a fixed point, at the same instant. It is best to take a number of these, say three or five, so as to check; and if the telescope is reversed and another set taken, the mean of the two sets will eliminate many inaccuracies. It is also an advantage to use the lower limb of the sun in the morning and the upper limb in the afternoon, it being easier to judge the tangency of image and cross wires. Allowance is then made for the semi-diameter of the sun, which varies from 15% to 16% minutes. 142 W. & L. E. GURLEY, TROY, NEW YORK It will be sufficiently close to have the vertical wire bisect the sun, but the altitude must be taken with care. The transit must be accurately leveled and adjusted. To reduce the observations there are many forms, all deduced from the same formula. The form much favored is tan' A = * REDUCTION FORMULA. In which "A" is the azimuth of the sun or horizontal distance from the meridian, and "S" is one half the sum of (90 altitude, corrected for refraction) + (90 latitude) + (90 declina- tion). Note the sign of the declination. When the declination is South this term would be 90 ( declin- ation) =r 90 -f~ declination. TRANSIT INSTRUMENTS 143 EXAMPLE. Place, Troy, N. Y. Time, 3h. 30m. P. M., March 31, 1917. The horizontal angle from a fixed point to sun's center 241 46' Observed altitude of upper limb of sun ... 30 31' 10" Obs. alt. refraction 1' 40" semi-diameter 16'= alt of sun's center 30 13' 30" Decimation for day and hour . . \ . . . 4 02' 58" Latitude 42 44' 90 alt. = 59 46' 30", 90 dec. = 85 57' 02", 90 lat. = 47 16', 2 S = 192 59' 32" S = 96 29' 46" log. sin [ S (90 alt ) ] = 9.77664 log. sin [S (90 lat)] = 9.87923 9.65587 log. sin S= 9.99720 log. sin [S (90 dec.) ] = 9.26251 9.25971 log. tan2 y 2 A = 0.39616 log. tan % A = 0.19808 y 2 A = 57 38' 06" and A = 115 16' 12" west of North. If in the morning would be east of North. Apply this to the horizontal angle from the fixed point to the sun and we have 357 02' 12", which is the reading of the horizontal limb when the telescope is pointed North. Set this reading off on the limb and the telescope will be in the plane of the meridian. 144 W. & L. E. GURLEY, TROY, NEW YORK TABLE OF MEAN REFRACTIONS DUE TO ALTITUDE BAROMETER 30", THERMOMETER 50 F Apparent Altitude Mean Ref. Apparent Altitude Mean Ref. Apparent Altitude Mean Ref. Apparent Altitude Mean Ref. 5 6 7 8 9 9' 46" 8' 23" 7' 20" 6' 30" 5' 49" 10 12 14 16 18 5 16" 4 25" 3 47" 3 19" 2 56" 20 25 30 35 40 2' 37" 2' 03" 1' 40" 1' 22" 1' 09" 50 60 70 80 90 0' 48" 0' 33" 0' 21" 0' 10" 0' 0" TABLE OF SEMI-DIAMETERS OF THE SUN Jan. 1, 16' 18" April 1, 16' 02" July 1, 15' 46" Oct. 1, 16' 01" Feb. 1, 16' 16" May 1, 15' 54" Aug. 1, 15' 48" Nov. 1, 16' 09" Mar. 1, 16' 10" June 1, 15' 48" Sept. 1, 15' 53" Dec. 1. 16' 15" SURVEYORS COMPASSES 145 COMPASSES THE Surveyors Compass is used considerably for farm surveys, for subdividing land, for retracing old lines, which were run originally with a mag- netic needle, for exploration and for other similar work. It consists of a magnetic needle swinging in a gradu- ated compass circle mounted on a plate, to the ends of which two slotted standards or sight vanes are attached in line with the zeros of the graduations. There are two levels to show when the plates are horizontal, and a socket on which the instrument can be turned to bring the sights into line with the object sought. The spindle on which this socket turns terminates in a ball and socket joint to enable the plates to be leveled. The Surveyors Compass has a romantic history as it is associated with the early settlement of our country. In 1748 George Washington, at the age of 16, took up the practice of surveying, and the compass of today is a development of the instrument used by him for land surveys in Virginia. Gurley Compasses were first used in 1845 and the accuracy of their service is testified by records which are on file in county seats throughout the country. 146 W. & L. E. GURLEY, TROY, NEW YORK VERNIER COMPASS THE superiority of the Vernier Compass over the Plain Compass consists in its adaptation to retrac- ing the lines of an old survey and to the surveys of the United States public lands, in which the lines are based on a true meridian. MAGNETIC NEEDLE. A bar of special magnet steel being saturated with a magnetic charge is suspended on a cup shaped jewel that rests on the fine point of the center pin or pivot, about which it turns with practically no friction so that it may assume its position in the mag- netic meridian. The ends are pointed and swing close to the graduated circle from which the angular bearing is read. MAGNETIC DECLINATION. It is well known that the magnetic needle deviates more or less to the east or west of a true meridian, or north and south line. This devia- tion, which is called the magnetic declination, is not constant, but increases or decreases to a very sensible degree. Thus, at London the needle pointed 11 east in 1580. This diminished until 1658 when it was zero, or the needle stood exactly north and south. The declin- ation continued westerly until 1812, when the bearing was 24 west. This has been gradually decreasing until in 1916, it was about 15 west. Thus a compass bearing at London changed from 11 east to 24 west, or a total of 35, from 1580 to 1812. The annual change was not uniform but varied from to 14 minutes of arc. SURVEYORS COMPASSES 147 The time periods taken for the needle to change from extreme eastern to extreme western declination vary with the locality. At St. Johns, Newfoundland, the period was about 180 years; at Trenton, N. J., 130 years and at Houston, Texas, 50 years*. At present the annual change is about zero in the middle west, four minutes on the Pacific Coast and six minutes in New Hampshire. For this reason, in running over lines from field notes of some years standing, the surveyor is obliged to make an allowance, both perplexing and uncertain, in the bearing of every line. It was to obviate this difficulty that the Vernier Compass was devised. To SET OFF THE DECLINATION. It will be seen that the surveyor having the Vernier Compass can, by mov- ing the vernier to either side, and with it, of course, the compass circle attached, set the compass to any declin- ation. He therefore places his instrument on some well defined line of the old survey, and turns the pinion until the needle of his compass indicates the same bearing as that given in the field notes of the original survey. Then, clamping the vernier, he can run all the other lines from the old field notes without further alteration. *From a speech at the Centennial Celebration of the N. S. C. fy G. S., made by Doctor Louis A. Bauer, Direc- tor of the Department of Terrestrial Magnetism of the Carnegie Institute, at Washington, D. C. 148 W. & L. E. GURLEY, TROY, NEW YORK The reading of the vernier on the limb in such a case would show the change of declination of the two diff- erent periods. The magnetic declination at any place being known, a true meridian, or north and south line, may be run by moving the vernier to either side, as the declination is east or west, until the arc passed over on the limb is equal to the angle of declination, and then turning the compass until the needle is made to cut the zeros on the graduated circle. The line of sights will then give the direction of the true meridian of the place. Such a change in the position of the vernier is nec- essary in surveying the United States public lands, which surveys are always run from the true meridian. THE LINE OF No DECLINATION, or the line upon which the needle will indicate a true north and south direction, is situated in the United States nearly in an imaginary line drawn from the middle of Lake Superior to Savannah, Ga. A magnetic needle placed east of this line has a declination to the west, and when placed west of the line the declination is to the east; and in both cases it increases as the needle is carried farther from the line of no declination. Thus, in Minnesota, the declination is from eight to eleven degrees to the east, while in Maine it is from fifteen to nineteen degrees to the west. At Troy, in the year 1919, the declination was about 12 33' to the west, and is increasing now in the same direction about 5.6 minutes annually. SURVEYORS COMPASSES 149 DIURNAL VARIATION. The magnetic declination does not remain constant through an entire day, but reaches its farthest point east about 8 o'clock A. M., and its farthest point west about 2 o'clock P. M. Conditions of temperature, magnetic storms and other causes at times affect the needle. Our own exper- iments show that different needles observed at the same time and under the same conditions differ in their direc- tion, but show nearly the same daily change. NEEDLE LIFTER. Underneath the main plate is a needle lifting screw which, by moving a concealed spring, raises the needle from the pivot, and thus prevents injury to the jewelled center as well as the blunting of the point during transportation or while carrying the instrument in the field. When the compass is not in use, it is the practice of many surveyors to let down the needle upon the point of the center pin, and allow it to assume its position in the magnetic meridian, so as to retain its polarity. After the needle has settled it should be raised against the glass for the reasons stated above. PLATE LEVELS. The spirit levels are placed at right angles with each other so as to level the plate in all directions, and are balanced upon a pivot under the middle of the tube, so as to be adjustable by a screw driver. OUTKEEPER. A small dial plate, having an index, turned by a milled head underneath, is used with this compass to keep tally in chaining. The dial is figured from to 16, the index being moved one notch for every chain run. 150 W. & L. E. GURLEY, TROY, NEW YORK BRASS COVER. A brass cover is fitted over the glass of the compass, and serves to protect it from accident, as well as to prevent electric disturbance. SIGHTS. The sights, or sight vanes, have fine slits cut through nearly their whole length, terminated at intervals by circular apertures, through which the object FIG. 39 No. 226 VERNIER COMPASS sighted upon is more readily found. Sometimes a horse hair or wire is substituted for half the slit, and placed alternately with it on opposite sights. SURVEYORS COMPASSES 151 The telescopic sight is often used with the Vernier Compass, and its adjustments and use are described on pages 158 to 165, TANGENT SCALE. The edges of the north sight of our compasses are graduated to half degrees for angles of elevation and depression respectively, which are read from corresponding peep sights on the south vane. The maximum angle which can be read is 23 degrees. BALL SPINDLE. The compass is fitted to a spindle made slightly conical, and having on its lower end a ball turned perfectly spherical, and confined in a socket by a pressure so light that the ball can be moved in any direction in leveling the compass. The ball is placed either in the brass head of the staff, or better, in the compass tripod. A leveling adopter, shown on page 158, is often used for more convenient leveling of the compass. THE STAFF MOUNTINGS consist of the brass head already mentioned, and a pointed steel shoe. The staff, to which the mountings should be securely fastened, may be procured from any wheelwright, or provided by the surveyor himself. CLAMP SCREW. In the side of the hollow socket of the compass is a screw by which the instrument may be clamped to the spindle in any position. SPRING CATCH. Besides the clamp screw there is fitted to the socket of our Vernier Compass No. 226, a spring catch, which, as soon as the instrument is set upon its spindle, slips into a groove, and thus removes all 152 W. & L. E. GURLEY, TROY, NEW YORK danger of the instrument falling from the spindle while being carried. USE OF THE COMPASS In using the compass, the surveyor should keep the south end toward his person, and read the bearings from the north end of the needle. The E and W letters on the face of the compass are transposed because the needle represents a fixed line, about which the compass box is revolved in directing the sight to the object observed. In sighting a point situated NW, the needle will point E of the line of sight, but it will correctly read NW in accordance with the line actually sighted, because the East quadrant is marked West. The compass circle being graduated to half degrees, a little practice will enable the surveyor to read the bearings to quarter degrees or even less, estimating with his eye the space bisected by the point of the needle; and as this is as close as the traverse table is usually calculated, it is the general practice. ANGLES OF ELEVATION. Having leveled the com- pass, bring the south end toward the person, place the eye at the little button, or peep sight, on the right side of the south sight, and with the hand hold a card on the front surface of the north sight, so that its top edge will be at right angles with the graduated edge and coincide with the zero mark. Then, sighting over the top of the card, note upon a flagstaff, held near the com- pass, the height cut by the line of sight, move the staff up the elevation and carry the card along the sight until SURVEYORS COMPASSES 153 the line of sight again cuts the same height on the staff. Read off the degrees and half degrees passed over by the card, and this will be the angle required. ANGLES OF DEPRESSION. Proceed in the same man- ner, using the eyepiece and graduations on the opposite side of the sight, and reading from the top of the sight. NEW AND OLD SURVEYS. When the compass is to be used in making new surveys, the vernier should be set at zero and clamped by the nut on the plate. In surveying old lines, the change of the magnetic declination should be ascertained by setting the compass on some well defined line of the tract, and making the bearing agree with that of the old survey, by moving the circle as already described. The circle can then be clamped, and the old lines retraced from the bearings given by the original surveyor. ELECTRICITY. Caution should be exercised in hand- ling the compass, that the glass face does not become charged with electricity excited by the friction of cloth, silk, or the hand, so as to attract the needle to its under surface. Should the glass become so charged, however, the electricity may be removed by breathing upon it, or by touching different parts of its surface with the moistened finger. Ignorance of this apparently trifling matter has caused the inexperienced surveyor much annoyance. 154, W. & L. E. GURLEY, TROY, NEW YORK COMPASS ADJUSTMENTS To ADJUST THE PLATE LEVELS. Bring the level bubbles into the middle by the pressure of the hand on different parts of the plate, and turn the compass half way around. If the bubbles run to the end of the tubes, it indicates that those ends are the highest. Lower them by loosening the screws under the lowest ends and tightening those under the highest ends until, by estima- tion, the error is half removed. Level the plate again, and repeat the first operation until the bubbles will remain in the middle during an entire revolution of the compass. To ADJUST THE SIGHTS. The sights may next be tested by observing through the slits a hair or thread, made exactly vertical by a plummet. Should the hair appear on the side of the slit, the sight must be adjusted by filing its under surface on the side which seems the highest. To ADJUST THE NEEDLE. Having the eye nearly in the same plane with the graduated rim of the compass circle, with a splinter of wood or an iron wire bring one end of the needle in line with any prominent graduation of the circle, as the zero or the ninety degree mark, and notice if the other end corresponds with the degree on the opposite side. If it does not, use the small brass wrench furnished with our compasses, and bend the center pin about one eighth of an inch below the point, until the ends of the needle are brought into line with the opposite degrees. SURVEYORS COMPASSES 155 Then, holding the needle in the same position, turn the compass half way around, and note whether it now cuts opposite degrees. If not, correct half the error by bending the needle, and the remainder by bending the center pin. The operation should be repeated until perfect reversion is secured in the first position. This being obtained, it may be tried on another quar- ter of the circle. If any error is there manifested, the correction must be made in the center pin only, the needle having been already straightened by the previous operation. When again made to cut, it should be tried on the other quarters of the circle, and corrections made in the same manner until the error is entirely removed, and the needle will reverse in every point of the graduated surface. REPAIRS TO THE COMPASS To enable the surveyor to make such repairs as are possible without recourse to an instrument maker, we add a few simple directions. NEEDLE. The magnetic needle is the most vexatious and troublesome part of a surveyor's instrument, and its imperfect working is almost invariably due to a rough- ened or scratched jewel or to a dulled center pin, or to both, and rarely to loss of magnetism. Injuries to the jewel and center pin are generally caused by allowing the needle to swing on the pin when the instrument is transported or when it is carried in 156 W. & L. E. GURLEY, TROY, NEW YORK the field from one station to another. If the needle is sufficiently raised by means of the needle lifting screw so that there is- no contact between the jewel and the center pin, the most frequent cause of injuries will be avoided. A wire is coiled on the south end of the needle, and may be moved back and forth to counterbalance the vary- ing magnetic dip at the north end, as a needle which is perfectly balanced in one locality is frequently out of balance in a different latitude. It may sometimes happen that the needle has lost its polarity and must be remagnetized. To do this, proceed as follows: Unscrew the bezel ring that holds the glass face, and remove the needle. Pass each end of the needle from middle to extremity with a gentle pressure over the magnetic pole of a permanent magnet, describing before each pass a circle of about six inches radius, to which the surface of the pole is tangent, draw- ing the needle toward the body, and taking care that the north and the south ends are applied to the opposite poles of the magnet. Should the needle be returned in a path near the magnetic pole, the magnetism induced by the contact of the needle with the magnet, in the pass just described, would be reversed, and the magnetic virtue almost entire- ly neutralized at each operation. When the needle has been passed in this manner about twenty-five times in succession, it will be fully magnetized. CENTER PIN. The center pin should occasionally be examined, and, if much dulled, should be taken out SURVEYORS COMPASSES 157 with the brass wrench or with a pair of pliers, and sharpened on a hard oilstone, the operator placing it in the end of a small stem of wood, or in a pin vise, and delicately twirling it with the fingers as he moves it back and forth at an angle of about thirty degrees with the surface of the stone. When the point is made so fine and sharp as to be invisible to the eye, it should be smoothed by rubbing it on the surface of a soft and clean piece of leather. To REPLACE A LEVEL VIAL. See instructions under transits, page 66. ATTACHMENTS FOR VERNIER COMPASS LEVELING ADOPTER. For more convenient leveling of the compass, as well as other instruments, we make a Leveling Adopter, No. 241, which is screwed to the top of the tripod like the leveling head. It can be used with a simple ball spindle and can be supplied with Compass No. 226. The instrument is made approximately level upon the ball and finally made truly horizontal by the level- ing screws. LEVELING HEAD. We also make for use with Com- pass No. 226 a Leveling Head, No. 242, consisting of arms strongly ribbed with four leveling screws having dust caps, and with clamp and tangent movement. This Leveling Head furnishes a stable support for the instrument, and affords the same conveniences for leveling and accurate adjustment in azimuth as the leveling heads on transits or levels. 158 W. & L. E. GURLEY, TROY, NEW YORK TELESCOPIC SIGHT. This telescope is attached to a movable band which, as shown in the illustration, can be slipped over the sight of a compass, clamped at any point desired, and adjusted with a screw driver and a steel adjusting pin. No. 241 FIG. 40 No'. 241 LEVELING ADOPTER To put this attachment in place, slip the band over the south sight of the compass, having the telescope at the right hand and the clamp screw on the outer surface of the sight, placing the band as low as will allow the SURVEYORS COMPASSES 159 telescope to revolve without striking the compass. This place should be marked by a line across the sight, or by a screw or pin on the inner surface of the sight, that the band may be set at the same point in subsequent use. FIG. 41 No. 242 LEVELING HEAD To fasten the band to the sight, bring up the clamp screw with a pressure just sufficient to hold the band to its place, tighten the screw on the left until the band is 160 W. & L. E. GURLEY, TROY, NEW YORK against the right edge of the sight, and finally tighten the clamp screw. To focus the telescope, turn the end of the eyepiece by the spiral motion of the tube until the cross wires are brought into distinct view. The objective is then FIG. 42 NO. 262 TELESCOPIC SIGHT, WITH ATTACHED VERTICAL CIRCLE NO. 265, LEVEL ON TELESCOPE NO. 266, AND CLAMP AND TANGENT NO. 267 moved in either direction by the pinion on the side of the telescope, until the object is clearly seen. SURVEYORS COMPASSES 161 The optical axis of the Telescopic Sight is at one side of the line of sight of the sight vanes, but parallel with it. The difference between a sight taken with the sight vanes and one taken with the telescope is so small that it may be disregarded in any survey made with the magnetic needle. If all the lines are run with the Tele- scopic Sight, the angles measured will be as accurate as if the optical axis of the telescope was in the line of sight of the sight vanes. The telescope is nine inches long, has a power of about 20 diameters and is furnished with stadia wires in addition to the cross wires. OFFSET STANDARD. When desired, the Telescopic Sight may be mounted upon an Offset Standard with Counterpoise, and so arranged that the line of sight is in line with the zeros of the compass circle. When in use, this standard with the telescope attached, is substi- tuted for the south sight of the compass. When furnished with a new instrument the telescope is packed in the box with the compass, but it can be safely sent by mail to any part of the country, packed in a case in which it may be kept when not in use. In the illustration on page 160, the telescope No. 262 is shown fitted with a vertical circle, a level, and clamp and tangent. For simple sighting, the level and circle can, of course, be dispensed with, but in the use of the stadia they are very desirable. When measurements are to be recorded in chains and links, the stadia wires should be made to cover one 162 W. & L. E. GURLEY, TROY, NEW YORK foot at a distance of sixty-six feet; if recorded in feet, the wires should cover one foot at a distance of one hundred feet. The rod used with the stadia should be graduated to feet and decimals of a foot. The various styles of rods are more fully described on pages 206 to 237. FIG. 43 COMPASS FITTED WITH NO. 262 TELESCOPIC SIGHT HAVING LEVEL, CLAMP AND TANGENT AND VERTICAL CIRCLE, MOUNTED ON NO. 268 OFFSET STANDARD WITH COUNTERPOISE SURVEYORS COMPASSES 163 In using the stadia, the lower wire is brought by the tangent screw precisely upon an even foot graduation of the rod, the upper wire is read, the smaller reading subtracted from the larger and the distance recorded. ADVANTAGE OF THE TELESCOPE. The advantage of the telescope over the sight vanes is readily apparent. Much longer sights can be taken, either fore or back, and lines run up and down steep hillsides with the same facility as on level ground, and with mor? accuracy, and with great relief to the eyes of the surveyor, often se- verely strained by the use of the sight vanes of the compass. Indeed, it may be said that with this simple attachment every compass can be transformed into a transit compass, and the advantages of the telescope brought within the reach of every surveyor, at small cost. To ADJUST THE TELESCOPIC SIGHT To make the adjustments, and indeed to do any correct work with a compass, the level bubbles should remain in the middle when the instrument is turned upon its spindle, and the sights should trace a vertical line when the compass is level. The means of effecting the adjustments will be understood by referring to page 164. TELESCOPE Axis. To make the telescope axis hori- zontal, the compass being in good order, first bring the levels into the middle and place the band in position upon the sight, as before described. Focus the tele- 164 W. & L. E. GURLEY, TROY, NEW YORK scope, and set the vertical cross wire on the edge of a building, or a long plumb line, 50 to 60 feet distant. If the vertical wire is not parallel with the edge or line, loosen the capstan head screws and turn the diaphragm by the screw heads until the correction is made, then tighten the screws. Next, sight at a point on the edge or line, near the ground. Clamp the compass to the spindle, and point the telescope to the top of the building or line. If the wire strikes to the right of the edge, it shows that the right end of the telescope axis is the lowest. To raise it, loosen the screws, B B, C C, which hold the piece containing the axis of the telescope, and by the screws, D D, the lower of which should be unscrewed and the upper one tightened, raise the telescope until the wire will follow the vertical line. If the cross wire strikes to the left when the telescope is raised, proceed exactly the re- verse in making the correction, until the wire will follow the edge from one. end to the other. LINE OF COLLIMATION. To bring the line of collima- tion into a position at right angles with the axis of the telescope, so that the cross wires will indicate two points in opposite directions in the same straight line, proceed as directed for transits on pages 77 to 79. SURVEYORS COMPASSES 165 ADJUSTMENT OF TELESCOPE TO THE SIGHTS. Find an object from three hundred to four hundred feet dis- tant, which the sight vanes will intersect. Clamp to the spindle and sight through the telescope at the object. If the vertical wire strikes to the right, loosen the screws B B, and screw up those in front, marked F F, the ends only of which are shown in the figure, until the vertical wire bisects the object, looking again through the vanes to see that the same object is seen through both telescope and sights. If the cross wire should strike to the left of the object, proceed in a manner exactly the reverse until the error is corrected. 166 W. & L. E. GURLEY, TROY, NEW YORK COMPASS WITH LIMB AND TELESCOPE 1920 MODEL This new model was designed to meet the needs of engineers and surveyors who do not have constant use for an expensive transit and yet desire an instrument which will enable them to do a greater variety of work than is possible with the ordinary sight compass. It is a highly developed form of a Telescope Compass and has the added characteristics of a light Transit; thus it can be successfully used for ordinary land sur- veying, preliminary or reconnoissance surveys, mine surveys, etc., in fact for a variety of work in which rapidity, ease of operation and portability, rather than extreme accuracy, are the essential factors. Engineers and Surveyors, as well as Explorers, will find this instrument a desirable addition to their equipment, enabling them to reserve their valuable Transits for pre- cise work. The needle is of unusual length for such a compact instrumnt, making it ideal for accurate com- pass surveys. The weight of the compass without the tripod is seven and one quarter pounds and the tripod weighs about four and one half pounds. SURVEYORS COMPASSES 167 FIG. 44 No. 294 COMPASS WITH LIMB AND TELESCOPE SUPERSEDING INSTRUMENTS PREVIOUSLY LISTED AS NO. 293 AND NO. 293-A 168 W. & L. E. GURLEY, TROY, NEW YORK POCKET COMPASSES WE manufacture a variety of small instruments which are so portable and at the same time so efficient that they are often used, in preference to the larger ones, for preliminary or reconnoissance work. FIG. 45 No. 285 POCKET COMPASS WITH LIMB SURVEYORS COMPASSES 169 POCKET COMPASS WITH LIMB The limb of this compass is five inches in diameter, graduated to half degrees and figured like limb I page 36. The vernier which is placed at an angle of 30 minutes to the line of sight reads to single minutes. The needle circle is graduated to half degrees and is figured from to 90 each way. The needle is three and one half inches long and the magnetic declination can be set off to single minutes. The sights fold down closely for convenience in packing and are made half slit and half hair so that back sights may be taken without turning the limb. This instrument can be used for a great variety of work and with the light extension tripod is especially adapted to surveys of mines where angles must be taken independently of the needle. 170 W. & L. E. GURLEY, TROY, NEW YORK GEOLOGISTS COMPASS This compass has proven admirably adapted for topographical work, and has been adopted by the U. S. Forest Service for the use of field men in making forest surveys and maps. If properly used, accurate work can be done with this small and compact instrument. It is made of aluminum to decrease weight and has a needle 2% inches long enclosed with its compass circle in a circular box set on a plate 4 inches square. With the improved needle lifter as shown, a water and dust- proof needle box is assured. The edges of this base are beveled and graduated, two for a tangent scale and two to inch scales. One of these latter is graduated to eighths, each of which repre- sents ten chains, and the other is decimal. The compass circle is made movable, and by a vernier attached to it on the inside the magnetic declination may be set off to 5 minutes. On the under side of the plate is a township plat. On the compass face is an arc of 180 degrees figured on each side of the line from to 90. A weighted pendulum hung from the center pin indicates, by its pointer on this arc, the angle of slope, when the com- pass is placed so that it rests on its west edge. On the outside of the box containing the compass circle is a movable circle, beveled and graduated on its upper edge and figured from to 90, and having at each quadrant a slit for sighting. SURVEYORS COMPASSES 171 FIG. 46 No. 335 GEOLOGISTS COMPASS U. S. FOREST SERVICE PATTERN 172 W. & L. E. GURLEY, TROY, NEW YORK Two tall folding sights are attached to the edge of the circular box, one having a slit and the other a hair. Two levels are placed at right angles with each other upon the base. The compass is supported on a simple ball spindle and socket, with staff mountings, and is usually carried in a leather pouch with shoulder and belt straps. Such a pouch can be supplied for an extra price. The staff cap is slotted to allow vertical angles to be read by means of the pendulum while the compass is on the staff or tripod. Tripods Nos. 416, 421 and 426 are suitable for use with this compass. SURVEYORS COMPASSES 173 THE Dip Compass consists essentially of a magnetic needle so suspended as to move readily in a vertical direction, the angle of inclination, or "dip," being measured upon the graduated rim of the compass circle. When in use, the ring or ball is held by the hand, and the compass box by its own weight assumes a verti- cal position. It must be held in the plane of the magnetic meridian. In this position the needle, when unaffected by the attraction of iron, assumes a horizontal line, as shown by the zeros of the circle. When brought over any mass of magnetic iron ore it dips, and thus detects the presence of such ore with certainty. If the Dip Compass is held horizontal, it serves as an ordinary pocket compass, and indicates the magnetic meridian, in the plane of which it should be held when used to ascertain the dip. Dip Compasses have a 3 inch needle, provided with a stop which is released by screwing down the clamp in the ball. The new style needle clamp enables the instrument to be held and controlled to the best advan- tage. The improved form of needle release is positive in action, durable in construction and not liable to in- jury. The Compasses have the two sides of glass and are furnished with removable brass covers. The needle of our Dip Compasses is adjusted to read at Troy, N. Y., when held in the plane of the mag- netic meridian, but it may read differently in another place. 174 W. & L. E. GURLEY, TROY, NEW YORK The readings of these compass needles are always relative and not absolute; therefore, if a needle is held in the plane of the meridian, in a place where it is known that there is no magnetic attraction, and the FIG. 47 No. 341-A DIP COMPASS reading is carefully noted; and the needle is then held in the plane of the meridian where magnetic attraction SURVEYORS COMPASSES 175 is suspected, a different reading will show the presence of some magnetic body, whether the needle is, in the first case, perfectly horizontal (reads to zero) or not. When in use the needle should always be held so that it will swing freely in the plane of the meridian, the stops being drawn entirely out of the way. When not in use the clamp should be unscrewed so that the needle is securely held. There is no instrument made which will indicate the presence of gold or silver. 176 W. & L. E. GURLEY, TROY, NEW YORK FIG. 48 No. 350 DIAL COMPASS U. S. GEOLOGICAL SURVEY PATTERN SURVEYORS COMPASSES 177 DIAL COMPASS A rough method of detecting the presence of large bodies of magnetic ore is by a compass directed in the meridian by means of apparent time on a Sun dial. Allowing for the magnetic declination for that location any variation by the needle from the magnetic meridian will indicate local attraction. This instrument, made of aluminum, has a needle two and five eighths inches long, and with its compass circle is enclosed in a circular box set upon a base 4 inches square, three edges of which are chamfered and graduated, the one on the W side of the compass into inches and tenths and the two others into degrees and half degrees, and figured from a center on the southwest corner of the base. The compass circle is movable, in order to set off the magnetic declination, and has a vernier attached to it on the inside, by which a graduated arc on the face of the compass is read to 5 minutes. With the improved needle lifter as shown, a water and dust-proof compass box is assured. The staff cap is slotted to allow vertical angles to be read by means of the pendulum while the compass is on the staff or tripod. There is also on the south side of the face an arc of 180 degrees, figured from to 90 on each side of the south or zero line of the face. A pendulum with index point hung from the center pin reads this arc when the compass is set up vertical on the raised south edge, thus making it a clinometer or slope measurer. 180 W. & L. E. GURLEY, TROY, N^w YORK FIG. 49 No. 3154 WOOD Box POCKET COMPASS SURVEYORS COMPASSES 180-A POCKET VERNIER COMPASS Nos. 300 AND 305 The Pocket Vernier Compass is an excellent and portable instrument for preliminary work, having a fine needle and a vernier and clamping nut, by which the sights can be placed at an angle with the line of zeros, so as to set off the magnetic declination as with the Vernier Compass No. 226. The instrument has folding sights, two levels and staff mountings, and is packed in a mahogany case. 180-B W. & L. E. GURLEY, TROY, NEW YORK We make two sizes of the Pocket Vernier Compass, having needles respectively three and one half and four and one half inches long. In the smaller instrument the sights have a slit in the south vane and a hair in the north vane, for readily finding an object; but in the larger size the sights are made half slit and half hair, as shown on page 180-A. Both sizes have the compass circle graduated to half degrees. In the smaller size the vernier of the variation arc reads to five minutes, and in the larger size to single minutes. The instru- ment may be used, if desired, upon a light tripod, No. 416, No. 421 or No. 426. When ordered, a rack movement with pinion is added, by which the magnetic declination may be set off more readily. , The compass with three and one half inch needle weighs about one and three quarters pounds; that with four and one half inch needle about two and three quarters pounds. LEVELING INSTRUMENTS 181 LEVELING INSTRUMENTS ENGINEERS WYE LEVEL OF the different varieties of leveling instruments, the Wye Level is universally preferred by American engineers on account of its accuracy, durability, ease and permanence of adjustment. We manufacture four sizes of Wye Levels, having telescopes, twenty-two, eighteen, fifteen, and twelve inches in length ; the smallest size is called the Architects Level. The illustration on page 182, represents the two largest sizes. TELESCOPE. The telescope has near its ends two rings of bell metal turned truly and of precisely the same diameter. On these rings it rotates in the wyes; or it can be clamped, when the clips of the wyes are brought down upon the rings, by pushing in the taper- ing pins. The telescope of the twenty-two inch and eighteen inch levels has a pinion movement to both the objective and eyepiece slides, and an adjustment for centering the eyepiece slide, shown at AA in the sectional view, Fig. 51, page 183. The arrangement for insuring the accurate projection of the objective slide is also shown at C, in the same illustration. Both of these adjustments are protected from disturbance by thin cover bands which screw over them. The objective slides of the fifteen inch and the twelve inch levels have pinion movements but the eyepieces have spiral or screw motions. 182 W. & L. E. GURLEY, TROY, NEW YORK K W PH PH O O O U 02 02 W K ^ A W W H H 5 5 G<1 00 cc 8 '- g GURLEY PRECISE ROD, MOLITOR PATTERN The Precise Leveling Rod, Molitor Pattern, as shown on page 224, is of T-shaped section, 12 ft. long, and is graduated to feet, tenths and hundredths. It can be graduated to millimeters, if desired. It is equipped with a circular level, two wooden handles, a plumb- ing attachment and plum- met, an enclosed thermome- ter, a canvas case and a turning point. It is packed in a special pine box with hinged cover, handles and lock. GURLEY SELF-READING TAPE LEVELING ROD The Tape Rod is a self- reading rod of decidedly different design from the Philadelphia Rod. It is a wooden rod, made in one piece with a metal roller set in it near each end. Pass- ing over these rollers is a continuous steel band twenty feet long and one-tenth foot wide, on the outside of which, for its entire length, liJU 226 W. & L. E. GURLEY, TROY, NEW YORK is painted a scale graduated to feet, tenths and half- tenths, with the details of the numbers so designed that readings to the nearest one-hundredth of a foot can readily be read. It is provided with a clamp so that the metal band, or tape, can be set at any desired reading and held firmly in that position. Where there are a large number of elevations to be calculated, it will save much time to use a tape rod which is so arranged that no elaborate figuring is required. In this rod, the numbers increase from the top toward the bottom, the opposite way from ordinary rods. The level is set up at a conven- ient point and the rod held on a bench mark. The tape, or band, on the rod is then moved up or down as directed by the levelman until he reads the feet, tenths and hundredths which are the same as those of the elevation of the benchmark, e. g., if the elevation of the B. M. is 195.62, the tape will be moved until it reads 5.62. If the rod is then held on a point 1.61 feet lower than the bench, the rod-reading will be 4.01, since with this rod the readings decrease as the rod is lowered. The elevation of the point is then 194.01 feet, or sufficiently precise for topographic work, 194.0 feet. In this way the elevations are read directly on the rod to feet and decimals of feet, the tenths and hundredths of feet being' supplied mentally. Obviously the only notes kept are the columns of stations and elevations. The rod is 10 ft. 8l/> inches long and graduated on one edge to feet and tenths. A canvas case can be supplied for the above rod. LEVELING INSTRUMENTS 227 FIG. 82. GURLEY PRECISE LEVELING ROD No. 550-R 228 W. & L. E. GURLEY, TROY, NEW YORK GURLEY PRECISE ROD WITH TURNING POINT AND PLATE The Precise Leveling Rod, as shown on page 227, is made in the cross-shaped section and is graduated on three faces to yards, tenths and hundredths. It reads to 3^/2 yards, and has silver-faced plugs at each half yard enabling it to be checked to a steel tape of standard length. It is fitted with wooden handle, thermometer, and fixed circular rod level. In addition there is a canvas case and a turning point and plate, all neatly packed in a special pine box with hinged cover, handles and lock. LEVELING INSTRUMENTS 229 FLEXIBLE OR POCKET LEVELING RODS The flexible self-reading rod is a convenient form where extreme accuracy is not essential and where ease in carrying is desirable. It is made of specially pre- pared canvas, so treated as to insure permanence in length within reasonable limits,, and is graduated on its painted surface to feet, tenths, and hundredths, or to special design. In use it is fastened to a board with thumb tacks, and can be rolled up easily and carried in the pocket in tin case with which it is provided. FIG. 83 Nos. 525-B TO 528 FLEXIBLE OR POCKET LEVELING RODS W. & L. E. GURLEY, TROY, NEW YORK cc IQ c r: id 6 X METRIC RODS Besides the usual gradua- tion of leveling rods into feet and parts of a foot, we grad- uate them, when desired, into meters, decimeters and centi- meters, without extra charge. The scales on the targets and sides of the rods read the centimeters to millimeters on all except the Telemeter, Tel- escopic and Plain Rods, which have no targets and are read only to centimeters. The New York, and Architects metric rods are graduated, when de- sired, to read by vernier to one-tenth of a millimeter. COMBINED LEVELING POLE AND FLAGSTAFF Nos. 530 AND 531 The Leveling Pole, No. 530, is a combination of a plain self-reading rod and a flagstaff. It is made with flat face, front and rear, and rounded sides. One face is graduated to feet and hundredths of a foot, while the other face and sides are graduated to feet only and are painted red and white alternately. LEVELING INSTRUMENTS 231 The pole is made 7 and 9 feet long, the graduated faces reading to 6 and 8 feet, respectively, and when used as a rod is read as shown in the illustration. WOODEN FLAGSTAFFS Nos. 534 TO 538-B w Wooden Flagstaffs, or Ranging Poles, o Nos. 534 to 536 are made in three sizes and ^ are octagonal in form, tapering from the bottom to the top, and have metal shoes. g They are graduated to feet, and painted al- < ternately red and white. When desired they are graduated metrically, five spaces to each w meter. J Jointed Wooden Flagstaffs Nos. 537-A to P 538-B are especially designed for convenience fc in use and for ease in carrying when travel- ^ ing. They are about 1 inch in diameter, and are made in equal length sections, which are - 1 firmly joined together by protected metal 5 screw joints. If desired, a heavy canvas * case is furnished to contain the several parts, H and to protect them from injury in trans- inches long. FIG. 100 TRAVERSE PLANE TABLE MOVEMENT, SHOWING THE TRIPOD HEAD AND LEGS, THE PLUNGER CLAMP SCREW, AND THE IMPROVED SPRING BOARD PLATE PLANE TABLES 259 The alidade consists of a brass ruler 10 inches long, graduated on the beveled edge to a scale of 40 parts to the inch, and having at each end* hinged sights which fold close to the surface of the ruler. One sight has a slit and the other a hair. The alidade is furnished with a leather pouch. FIG. 101 No. 590-A POCKET SIGHT ALIDADE, WITH FOLDING SIGHTS \\ POCKET SIGHT ALIDADE No. 590-A is 6" long and has hinged sights which fold down flat on the ruler. *j The beveled edge is graduated the entire length to read 1/10 and 1/20 of a mile for ratios of 1/90,000 and 1/45,000 .respectively. The middle part of the edge is further divided to read 1/50 and 1/100 of a mile respectively for the same two ratios. This alidade is furnished with leather case having pencil pockets. 260 W. & L. E. GURLEY, TROY, NEW YORK ARMY SKETCHING CASE THIS instrument for topographic map making was originally designed especially for the use of U. S. Army Engineers, but since its introduction has been found unusually serviceable for a similar class of work by foresters, geologists, road engineers, timber cruisers and civil engineers. Several hundreds of these efficient field sketching outfits are being used successfully by officers and men in practically every branch of the Army and by the various Army Service Schools; also by military acad- emies, militia organizations, civil engineers and sur- veyors. In addition to the simplicity and strength of con- struction fitting it for general use, this sketching case possesses a unique feature in that the board does not require to be oriented in taking observations. So far as we know, this is the only practical sketching case on the market having this valuable feature, which makes its operation very simple and rapid. The use of a tripod is unnecessary and there is no complicated protractor to operate. In fact, anyone can readily learn to use this instrument after studying the directions carefully. CONSTRUCTION , The Army Sketching Case consists of a plane table board, six inches by twelve inches, made of seasoned pine with mahogany end pieces. This construction in- sures a strong, durable board which will not warp nor PLANE TABLES 261 pull apart under hard service. To the lower right hand side is attached a compass box with floating dial, three inches in diameter, beveled on the edge and graduated into 360 degrees. A protected opening in the compass box permits the graduated dial to be read either from above or when the board is held level with the eye of the observer. I FIG. 102 No. 594 ARMY SKETCHING CASE PATENTED SEPT. 1, 1908 Designed by Lt. Col. Glenn S. Smith of the U. S. Geological Survey 262 W. & L. E. GURLEY, TROY, NEW YORK Rifle sights which are placed in line with the center of the compass and parallel with the edge of the board, are used as an alidade in taking bearings. On the upper side of the board is mounted a circular plate, six inches in diameter, and pivoted at the center. This plate is attached to an L-shaped base at the upper end of which is a cylinder through which passes a rod parallel with and secured to the top of the board. A metal strip let into a slot in the middle of the board guides the lower edge of the L-shaped base. Upon the guides as described, the base carrying the circular plate can be moved from side to side over the upper surface of the board and clamped at will by a set screw in the cylinder at the top. A clamp with index line is so attached to the base that the circular plate mounted upon it may be set at any desired position. A card of aluminum is attached to the circular plate and upon this card a combined protractor and scale are printed. The protractor is graduated into 360 degrees and the scale consists of a series of equally spaced concen- tric circles. Different protractor cards are furnished for the various scales used in map making. Rollers with friction brakes, attached to two edges of the board, receive the paper and hold it snugly against the surface of the protractor which travels underneath PLANE TABLES 263 it. An aluminum shield protects the paper and pre- vents soiling. To the under side of the board a swiveling strap, with buckle, is attached, by means of which the case can be firmly secured to the observers arm. There is also a socket by which a tripod or staff may be attached. A simple clinometer attachment for taking slopes is also provided. As far as possible the metal parts are made of alum- inum, so that the case weighs only about two pounds, and they are of dark finish to avoid reflection of sun- light. Care in the selection of a proper material for use On the case in recording observations is essential to successful operation, and tracing cloth should be avoided as too smooth for the use of a pencil. Vellum tracing paper has a slightly roughened surface, little affected by moisture and on which the pencil works well, is recommended. On completion of the survey, the sketch may be taken from the instrument and blue prints made directly from the original. Detailed directions for using the Army Sketching Case are furnished with each instrument. A descriptive circular containing these instructions will be sent free to any address on request. 264 W. & L. E. GURLEY, TROY, NEW YORK FIALA SCOUT SKETCHING CASE The interest in map sketching as practiced by army engineers is increasing, and the necessity for a more general knowledge along these lines is evidenced by the taking up of such work by various organizations of the National Guard. FIG. 103 SHOWING METHOD OF USING FIALA SCOUT SKETCHING CASE For convenience in making maps in the field various forms of sketching cases are used, consisting of a small drawing board provided with a magnetic compass, ali- PLANE TABLES 265 dade (or scale) with sights, and rollers for carrying a supply of paper. Sketches are made with colored pencils. With such equipment, topographical maps can he accurately and rapidly made to show the character of the land, whether level or mountainous, fertile or barren ; the location of railroads, highways, water courses, and bridges or structures of any kind. Map making is a very necessary part of a Boy Scout's course in surveying. By means of a sketching case he can make a record of the country traversed on his "hikes," and thus develop his sense of proportion, direction and distance in an instructive and interesting manner. Canoeists and campers also can use a device of this kind to advantage. The Fiala Scout Sketching Case is a practical instru- ment in every particular. It was designed and made from suggestions by Mr. Anthony Fiala, the explorer, whose experience in the Arctic regions and with Colonel Roosevelt in South America places him in a position to fully understand the needs of those engaged in outdoor pursuits. 266 W. & L. E. GURLEY, TROY, NEW YORK Designed along the same general lines as the Army professional model,, No. 594, which we have made for a number of years for military topographers and others, the Fiala case is much less elaborate and expensive but is efficient and convenient as well as of value for educa- tional purposes. FIG. 104 No. 596 FIALA SCOUT SKETCHING CASE The Fiala Scout Sketching Case consists of a thoroughly seasoned white pine drawing board, 6 inches wide x 5 inches long, having % inch diameter rollers at each end which carry a strip of white, strong, smooth- faced architects paper, 5% x 36 inches. An adjustable device on the rollers holds the paper flat against the board and prevents it from uncoiling. Fitted into the right hand end of the board is a brass compass having PLANE TABLES 267 a 1% inch needle with needle stop and slotted revolving cover. Holes bored into the left hand end of the board contain three sketching pencils, black, red and blue. These are held securely by means of a brass spring clip. A boxwood ruler, 6 inches long, with small brass folding sights at each end, enables the user to establish the bearings of lines. The ruler has scale of 6 inches to 1 mile on one edge, and 3 inches to 1 mile on the other. Two rubber bands are used to aid in holding the ruler on the paper. The ruler is fastened to one of the roller knobs by a cord and when not in use is securely held against the back of the board by a brass spring clip. There is a simple form of clinometer for determining angles of slope. The ruler alidade is arranged to swing across the surface of the paper and the angles of slope are read on a scale attached to the left hand edge of the case. In use, the sketching case is fastened to the forearm of the sketcher by a leather strap on the back of the board. It weighs about 30 ounces and measures 9 x 7% x 1 inch. Packed for parcel post shipment, it weighs 3 pounds. Architects Drawing Paper, in rolls 5% x 36 inches, per roll, is furnished for use with this case. 268 W. & L. E. GURLEY, TROY, NEW YORK CHAINS AND TAPES The Surveyors and Engineers Chains are the measur- ing instruments by which our oldest surveys were made and many farm surveys are made. We furnish tapes of all standard units and lengths in Nos. 8 and 10 refined iron wire and in Nos. 8, 10 and 12 best steel wire. Steel chains are preferred on account of their greater strength, although they are more expensive than those of iron. BRAZED STEEL CHAINS. A very light and strong chain is made of No. 12 steel, securely brazed. The wire is of a low spring temper, and the chain, though light, is almost incapable of being broken or stretched in careful use. METER AND VARA CHAINS. The meter is used as a standard measure of length in many countries, and chains of ten and twenty meters are often ordered. The chains are of Nos. 10 and 12 iron or steel wire, each meter being divided into five links. The old surveys of Texas were made with the vara as the unit of measure and we supply Vara Chains of Nos. 8, 10 and 12 iron or steel wire. CHAIN TAPES Chain tapes are generally used on bridge, road and street work, and as standards for comparison of other chains and tapes. They are made of a thin ribbon of steel about one quarter of an inch wide, and of straight CHAINS AND TAPES 269 spring temper, and in lengths of from sixty-six to five hundred feet. STEEL RIBBON CHAIN TAPES One-quarter inch wide, heavy steel ribbon, deeply etched graduations, large detachable handles and a wooden reel with nickel trimmings. The sixty-six and one hundred thirty-two feet lengths are usually graduated at each Gunter's link for use in land surveying, and the one hundred to five hun- dred feet lengths are graduated at each foot, with the first and last foot marked in tenths, for city work. METALLIC TAPES These are of linen, about five eighths of an inch wide, and have fine brass wires interwoven through their whole length. They are thus measurably correct, even when wet. They are graduated in feet and tenths or in feet and inches, on one side, as ordered, and are marked in links on the reverse side. They are wound in a leather case having a folding handle. STEEL TAPES The best tapes are made of a thin ribbon of steel in one piece, of straight spring temper, and either one quarter, three eighths or one half inch wide. They are made in all lengths from twenty-five to two hundred feet, graduated to feet, inches, and eighths 270 W. & L. E. GURLEY, TROY, NEW YORK of an inch, or more usually feet, tenths and hundredths of a foot. They are also graduated at each Gunter's link, on the reverse side if desired. The figures and graduations are etched on the surface of the steel. The Engineers Pattern steel tapes are made of thin steel ribbon, about one quarter of an inch wide and of straight spring temper. They can be detached from the case when desired, and used with a pair of handles for chain measurements. They can also be used with handles having a compensation scale for variations of temperature. These tapes are U. S. standard measure at 62 Fahrenheit, with about twelve pounds strain. A hun- dred foot tape expands .0756 inch for each 10 rise in temperature. The tapes are wound in a leather or metal case with folding handle. Our steel tapes Nos. 850 to 854-B are very popular for underground work. They are one half inch wide, and are mounted on an open brass frame, nickel plated, and with double folding flush handle. They are easily wound and unwound, and the open frame allows the evaporation of moisture. This feature is also character- istic of the reels supplied on our Wolverine Tapes Nos. 814 to 817. CHAINS AND TAPES 271 METRIC AND VARA TAPES We can furnish any of our metallic tapes, and steel tapes, with metric or vara measure on the reverse side instead of links. Tapes of metric or vara measure only can also be supplied. Our extra heavy metric chain tapes, Nos. M20 to Ml 00, are graduated with metric measure only, and are marked in decimeters, with the first meter in centimeters and the first decimeter in millimeters. If graduated with vara measure only, they are marked in tenths of a vara. MARKING PINS In chaining, eleven marking pins are needed, made either of iron, steel or brass wire, as preferred. They are about fourteen inches long, pointed at one end to enter the ground, and formed into a ring at the other end for convenience in handling. Marking pins are sometimes loaded with a little mass of lead around the lower end, to serve as a plumb when the pin is dropped to the ground from the sus- pended end of the chain. 272 W. & L. E. GURLEY, TROY, NEW YORK PLUMMETS We manufacture plain brass plummets like that illustrated in Fig. 105 in the following sizes: 6 oz., 10 oz., 16 oz., 24 oz., and 32 oz. If the work at hand requires a long plummet of small diameter No. 460 twelve ounce plummet is supplied. FIG. 105 Nos. 450 TO 458 PLAIN PLUMMETS PLUMMETS 273 ADJUSTABLE BRASS PLUMMET No. 465 has a con- cealed reel R, Fig. 106, around which the string is wound by turning the milled head on top. The friction upon the reel will hold the plummet at any desired point of the line. K FIG. 106 No. 465 ADJUSTABLE PLUMMET SHOWING DETAILS OF CONCEALED REEL 274 W. & L. E. GURLEY, TROY, NEW YORK HYDRAULIC ENGINEERING INSTRUMENTS THE importance of an exact knowledge concerning the surface water supply of the country has been recognized for many years. The immediate neces- sity of stream flow data, to be used by those interested in or engaged upon problems of hydraulic engineering,, including water power, domestic water supply, inland navigation, irrigation, swamp and overflow land drainage and flood prevention, has created a constantly increasing demand for a means of obtaining such data accurately. The data required is the area of cross-section, the velocity of flow and the elevation of the water, with which the quantity or volume of flow can be readily computed. The area of cross-section is obtained by the usual methods of surveying. Velocity is measured by Current Meter Measure- ments. The varying height of the water level is automati- cally recorded by Water Stage Register. HYDRAULIC ENGINEERING INSTRUMENTS 275 CURRENT METERS FOR more than thirty years W. & L. E. Gurley have made Current Meters under the patents of W. G. Price, the Assistant Engineer of the Corps of Engineers, United States Army, who in 1885 devised the initial pattern. The general features are retained in the latest models, although somewhat modified as the result of suggestions from many hydraulic engineers who have had large experience in current meter observation under all conditions of service. The many hundreds of Gurley Current Meters in use in all parts of the world, their constantly increasing sale and their accuracy and reliability under all con- ditions, show that they are the standard instruments for the accurate measurement of the velocity of water in streams and open conduits. A current meter for measuring the velocity of flowing water comprises two essential parts: (a) a wheel ar- ranged so that when suspended in flowing water the pressure of the water against it causes it to revolve; (b) a device for recording or indicating the number of revolutions of this wheel. The relation between the velocity of the moving water and the revolutions of the wheel is determined by rating each meter. The distinguishing characteristics of a good current meter are (a) simplicity in construction, with no delicate parts which easily get out of order; (b) a small area of resistance to the velocity of the water; (c) a simple 276 W. & L. E. GURLEY, TROY, NEW YORK and effective device for indicating the number of revolu- tions of the wheel; and (d) easy adaptability to use under all conditions. SELECTING THE PROPER TYPE OF CURRENT METER The experience of many years has shown that but two patterns of the Gurley meter are needed to ade- quately meet the requirements of practically all engineers engaged in measuring the flow of water. Accordingly, we have discontinued making the large pattern formerly listed as Meter No. 600, and also two of the smaller patterns, previously listed in different combinations as Meters Nos. 617, 618, 621 and 624. We will continue to make only the two standard models, namely Accoustic Meter No. 616, and Electric Meter No. 623. The latter may be supplied with such a variety of equipment that it will be the equivalent of, and can be used for the same work as, the discon- tinued Meters Nos. 617, 618, 621 and 624. The selection of a meter should be made after con- sideration has been given to the following factors: (1) The purpose for which the instrument is to be used. (2) The manner in which it is supported. (3) The amount of weight to be used. (4) The frequency of the revolutions to be indicated. HYDRAULIC ENGINEERING INSTRUMENTS 277 CURRENT METER No. 616. When it is possible for the observer to approach the stream closely, and to hold the meter in position by means of its suspension rod, FIG. 107 No. 616 ACOUSTIC CURRENT METER OUTFIT WITH JOINTED WADING RODS, RUBBER TUBE, EAR PIECE AND CONNECTION, INDICATING EACH TENTH REVOLUTION especially in channels of small depth, the Acoustic Cur- rent Meter, No. 616, is very useful. 278 W. & L. E. GURLEY, TROY, NEW YORK This meter indicates every tenth revolution of the bucket wheel by the sound of a hammer striking against a diaphragm, one blow for every 10 revolutions. The indicating mechanism is completely enclosed and thoroughly protected from injury. When in use the meter is held by a jointed wading rod, which screws into the frame and in connection with a rubber tube and ear piece attached to it, forms a passage through which the sound of the hammer stroke is transmitted to the ear of the observer. This enables him to count the number of revolutions of the wheel in any given space of time, and they by means of the rating table to ascertain the velocity of flow. THE ELECTRIC INDICATOR. Many observers prefer an electric type of revolution indicator. This indi- cating device is protected from injury by enclosure in the contact chambers, or commutation boxes, and the revolutions of the bucket wheel are indicated by a tele- phone ear piece, which is generally fastened in a con- venient position on the observer's coat. CURRENT METER No. 623 combines all of the advan- tages of all other meters previously listed. It can be suspended by cable or by jointed wading rod, and is equipped with two interchangeable commutator boxes for indicating each revolution, or each fifth revolution, of the bucket wheel. The combination of these features provides an outfit which has been adopted as standard by the most efficient hydraulic engineers. This meter is used extensively HYDRAULIC ENGINEERING INSTRUMENTS 279 by the Water Resources Branch of the United States Geological Survey, the leading organization devoted to the precise measurement of water. Two contact chambers, one to indicate each revolu- tion, the other each fifth revolution of the bucket wheel, FIG. 108 No. 623 ELECTRIC CURRENT METER OUTFIT WITH METER SUSPENDED BY JOINTED WADING RODS are provided. These contact chambers may be readily interchanged, the only change being in the shaft and consisting of the insertion of a cam on the end of the 280 W. & L. E. GURLEY, TROY, NEW YORK bucket shaft when a single revolution is to be indicated, or the insertion of a worm when it is desired to indicate every fifth revolution. A more complete description of current meters and their parts, as well as water stage registers, is given in FIG. 109 No. 623 ELECTRIC CURRENT METER OUTFIT WITH METER SUSPENDED BY CABLE "A Manual of Gurley Hydraulic Engineering Instru- ments", which will be sent upon request. The Manual, besides describing the meters, gives the calibration charts for the various types and full instructions regard- ing the use of hydraulic instruments in general. HYDRAULIC ENGINEERING INSTRUMENTS 281 ELECTRIC REGISTER WHENEVER it is desirable to record the revolu- tions of the bucket wheel of Meters Nos. 617, 621 and 623, an Electric Register may be substi- tuted for the telephone ear piece ordinarily used. Electric Register No. 609 has been developed recently by us and is a great improvement over the former pat- tern. It is suitable for use with current meters or any FIG. 110 No. 609 ELECTRIC REGISTER other intermittent contact device of which a record is desired. This device consists of a three figure "Veeder" counter operated by an electro-magnet and springs, and 282 W. & L. E. GURLEY, TROY, NEW YORK is so arranged that the same force acts on the counter regardless of how much current is used. This results in a uniform action and guarantees against any skipping or missing, under widely varying conditions. This instrument will operate under favorable condi- tions with one good dry cell, but should have two, as a protection against deterioration of the battery. It requires but 0.31 ampere with two cells, which is a much smaller current than was necessary with the old style register, and which will not burn the current meter contacts. There are no dials to read, the total result being shown directly by the figures, so that there is small chance of an error in reading. HYDRAULIC ENGINEERING INSTRUMENTS 283 FIG. Ill No. 628 HOOK GAGE HOOK GAGE THIS new type of Hook Gage was designed in accordance with suggestions made by Messrs. Metcalf and Eddy, Con- sulting Hydraulic Engineers, of Boston, Mass., and is a great improvement over other patterns. Its entire arrangement is such that the readings can be taken by the observer with the greatest possible convenience and at some distance from the surface of the stream or ditch being measured. This is often a decided advantage, especially so in the East, where many of the streams are contaminated by dye stuffs and other undesirable ma- terial, rendering it unpleasant for the observer to get too close to the water. The Hook Gage is nickel-plated throughout. The tube is regularly made to read to 2.2 feet but may be made longer if desired. It is grad- uated to feet, tenths and hundredths, and is read to thousandths by a ver- nier which is capable of fine adjust- ment by means of a slow motion screw. Elongated holes in the base furnish means for bolting the gage 284. W. & L. E. GURLEY, TROY, NEW YORK to the side of the flume. The hook is adjustable within the tube and allows for a movement of 12 inches inde- pendent of the gage, thus permitting it to be set accur- ately to the exact surface of the water. USE OF THE HOOK GAGE The hook gage is used in a box attached to a flume at any convenient point near the weir, the water from the flume being conveyed to the box by rubber or lead pipes, thus indicating the precise level of the water in the flume, the surface of the water in the box being at rest. When the depth of the water passing over a weir is required, the exact level of the crest of the weir should be taken by a leveling instrument and rod, and marked by a line drawn in the still water box at the surface of the water. The scale of the gage being previously set at zero with the vernier, the base is fastened to the box above the water in a vertical position and at such a height that the point of the hook is at the same level as the crest of the weir, the precise point being secured by moving the hook in the tube. The point of the hook will of course be under water and level with the crest of the weir. The depth of water flowing over the weir is the dis- tance between the point of the hook in the position named and the exact surface of the water. To ascertain this, the hook is raised by turning the milled head nut until the point of the hook, appearing a little above the sur- HYDRAULIC ENGINEERING INSTRUMENTS 285 face, causes a distortion in the reflection of the light from the surface of the water. A slight movement of the hook in the opposite direction will cause the distor- tion to disappear, and will indicate the surface with precision. The reading of the scale will then give the depth of water passing over the weir, in thousandths of a foot. It will be understood from the illustration that the longer movements of the scale are made by loosening the large clamp screw and sliding the graduated tube through the frame, the finer adjustments being made by the milled nut. 286 W. & L. E. GURLEY, TROY, NEW YORK WATER STAGE REGISTERS THE growing importance of water power develop- ment, the great possibilities for its use in irrigation and the many other ways in which this great gift of nature may be employed in the service of man, have made more essential, as in recent years its value has been better appreciated, the accurate determination of the volume of water in streams available for such use. The energy of some of the foremost engineers in the world has been enlisted in the work, and both methods and appliances have been perfected as the result of experience. For many years Gurley Current Meters have been in use in all parts of the world and are considered stand- ard in determining the velocity of the flow of water in streams. The discharge of a stream is usually ascertained by a comparison of gage heights with a rating table of the discharge of the stream at varying heights, com- piled from a series of current meter observations. The greatest error in these estimates is due to inac- curate determination of the gage heights, ordinarily secured from a few observations taken during the day, or even more infrequently. It has been found that on many streams there is a considerable daily fluctuation due to natural or artificial control, making it impossible to obtain accurate gage HYDRAULIC ENGINEERING INSTRUMENTS 287 heights without the use of an automatic register which will record the height of water at regular intervals dur- ing the entire twenty-four hours, or over a longer period of time. In the endeavor to produce instruments satisfactory for such purposes, we have for several years been en- gaged in designing Water Stage Registers by which the varying height of water in streams may be gaged and a dependable continuous record be obtained. As a result of our efforts, coupled with the sugges- tions made by eminent engineers, familiar with the problems involved, we have produced several patterns of Water Stage Registers which are satisfactorily meet- ing the demands of the service for reliable instruments giving accurate and uniform records. Automatic Water Stage Registers are divided into two classes those making a printed record, and those making a graphic record. In the first type a printed record of the height and time is made, while in the second type the record is traced by a pen or pencil on the surface of a paper sheet, moving in harmony with the time and height. The first type of register is designed to give printed records of the rise and fall of water continuously for a long period of time, and is especially adapted for places where it is impractical or impossible, by reason of inaccessibility, for the observer to visit the station for long intervals of time and where the record, to be of service, should be continuous. 288 W. & L. E. GURLEY, TROY, NEW YORK No. 630 PRINTING WATER STAGE REGISTER Patented January 10,, 1911 The difficulty of scaling with precision the records made by a graphic register, the tendency of the paper to be affected by moisture or other causes, and the lim- ited time for which the record can be taken, have led to our introducing a register which prints on a continuous paper strip, at intervals of 15 minutes, the height of the water in feet and hundredths of a foot for a period of time dependent on the range of fall allowed the driving weights, which move at the rate of one and one half inches during a period of 24 hours. This register is the result of years of study and experiment, and is made in the best manner and of the best material. It has had the original inspection and ap- proval of some of the most eminent hydraulic engineers, and has been tested under severe conditions of actual service with most satisfactory results. We, therefore, have no hesitation in recommending its use to all who require accuracy and efficiency in water measurements. CONSTRUCTION. By reference to the illustrations, a clear idea can be gained of the mechanical construction of the register. An iron base about fourteen inches square, at either corner of which is an iron rod approximately twenty-one inches long supporting an iron top, forms a frame for the register. On the base are also erected the standards HYDRAULIC ENGINEERING INSTRUMENTS 289 which support the recording mechanism, the spools for holding the paper and carbon ribbon and the driving mechanism. FIG. 112 SECTION OF PAPER TAPE, SHOWING PRINTED RECORD MADE ON A NO. 630 PRINTING REGISTER The recording mechanism consists of three parallel type wheels, on the faces of which are raised figures and divisions indicating respectively the period of time from one to twelve hours at intervals of 15 minutes, as desired, the number of feet from zero to thirty-six, and the hundredths of .a foot. 290 W. & L. E. GURLEY, TROY, NEW YORK FIG. 113 No. 630 PRINTING WATER STAGE REGISTER FRONT VIEW, SHOWING CLOCK, FLOAT AND WEIGHTS HYDRAULIC ENGINEERING INSTRUMENTS 291 The type wheel indicating time is controlled by a weight driven clock of finest construction, with full jeweled escapement and compensated to endure varia- tions of climate without variation in its regular operation. The two type wheels indicating heights of water are moved by a sprocket wheel connected to the float and counterweight by a perforated metal band, so that any change in the height of water is immediately indicated by a corresponding movement of the type wheels. Four reels mounted on the main standard of the instrument carry and receive the paper strip with its carbon backing on which the record is made, and which passes over the type wheels, and is held taut by the tension of a weight on the receiving reel. Three weighted hammers, pivoted on a shaft and with cushioned faces opposite the center of the type wheels, are controlled in their action by a saw-toothed cam, moved by the clock in such a manner that at inter- vals of 15, 30 or 60 minutes the hammers are released and strike a blow on the type wheels, thus making on the tape covering them an imprint of the indicated time, and height of water. The large diameter of the copper float, 10 inches, enables it to respond immediately to any variations in the height of the water, the slightest change being re- corded. Its size and shape render it extremely sensitive, and the top is rounded so that foreign matter cannot lodge on it and change the degree of immersion. 292 W. & L. E. GURLEY, TROY, NEW YORK The frame and mechanism as above described are covered by a metal hood, fitting tightly at the bottom in a rubber gasket and having at the top a clamp nut which may be secured by a lock, preventing the removal of the case by unauthorized persons. A glass-covered opening allows an easy reading of the clock, which may be wound from the outside at such intervals as required without the removal of the case or disturbance of the instrument. For the convenience of our customers we publish the "Manual of Gurley Hydraulic Engineering Instru- ments." This book describes in detail the construction and best methods of installing Gurley Hydraulic Registers. GRAPHIC WATER STAGE REGISTERS An improved Graphic Register is shown in Fig. 114 having several unique and valuable features. It is of simple construction, with few parts ; is designed for easy operation, and adapted for a wide range of conditions. Its construction is such that no lost motion will develop from continuous service and it can be operated with minimum care and expense. Vertical scales ranging from zero to twenty feet are supplied and time scales of 1 day, 4 days, or 7 days can be furnished. As the record of stage is made around the cylinder, there is no limit to the number of revolutions possible, and hence to the range of stage. Therefore, it is advisable to use as low a range as possi- HYDRAULIC ENGINEERING INSTRUMENTS 293 FIG. 114 No. 633 GRAPHIC WATER STAGE REGISTER SPRING-DRIVEN CLOCK 294 W. & L. E. GURLEY, TROY, NEW YORK ble and obtain a more accurate reading of the water stage. If occasionally the water stage is above the range of the register, no trouble will be experienced in reading the water level. Complete descriptions and illustrations of our hy- draulic equipment is furnished in "A Manual of Gurley Hydraulic Engineering Instruments/' which will be sent upon request. CONSTRUCTION The Graphic Water Stage Register combines admir- ably scientific design and rugged construction. An extra heavy, spring or weight driven clock is geared to two time screws which are supported at each end. Mounted on the screws is a carriage holding a weighted pencil, this carriage and pencil move forward without lost motion in accord with the turning of the clock shaft. A counterweighted float ten inches in diameter and three and one half inches thick operates the record cylin- der either directly or by means of gears according to the vertical range desired. The whole instrument is enclosed in a sheet metal cover which makes it waterproof and dust proof. HYDRAULIC ENGINEERING INSTRUMENTS 295 GURLEY LONG DISTANCE GRAPHIC WATER STAGE REGISTER AND INDICATOR AS the result of several years experimenting in co- operation with a number of leading hydraulic engineers, W. & L. E. Gurley have developed a Long Distance Water Stage Register which is the most accurate, efficient and reliable instrument of its type on the market. The value to engineers of segregating distant gage readings at one point is apparent. In power plant operation, particularly, the use of this instrument proves invaluable, as it provides means of determining instantly the varying water levels at distant points, and thus per- mits of a more efficient use and control of the water available. The outfit consists of a float-operated Sender which is installed at the gaging station and by which the vary- ing water levels are transmitted by means of an electric circuit to the Receiver, which is generally located in the power house or in the office of the engineer responsible for the efficient operation of the plant. The Receiver may consist of an indicating device only, or it may include a Register making a graphic record, or the apparatus may comprise a combination of both, as desired. Furthermore, it is possible, with one Sender, to operate several Receivers, of the indicating or recording type, at different locations. 296 W. & L. E. GURLEY, TROY, NEW YORK The Sender and the Receiver are of simple construc- tion and high grade workmanship and are very positive and uniform in their operation. FIG. 115 No. 637 LONG DISTANCE GRAPHIC WATER STAGE REGISTER In modern hydraulic practice it is often desirable to record or indicate in the office or power house, the water stage at some distant point. Gurley Long Distance Registers and Indicators are electrically operated and will record or indicate accur- ately the fluctuations of any liquid level at any distance. HYDRAULIC ENGINEERING INSTRUMENTS 297 THE SENDER, located at the point where the water stage is to be measured, is operated by a float and counterweight similar to those used on our other regis- ters. It is equipped with two electrical contacts, one of which closes for a fraction of a second every time the float rises, the other when the float falls 1/20 of a foot. These contacts, which were developed in the Gurley factory, have been subjected to tens of thousands of tests with heavy load at 120 volts, without any failure or even a sign of deterioration. THE RECEIVER consists of one of our No. 633 Graphic Registers, but modified so that the record cylinder is operated by magnets instead of directly by the float. The drum is turned by means of gears and a ratchet wheel which is operated by two pairs of powerful mag- nets, one for rising, the other for falling water. The operating arms which are attached to the magnet arma- tures turn the ratchet wheel one notch each time either magnet is energized. These arms also carry interlocking stops which positively prevent the wheel from turning more than one notch, until the magnet is released and ready for the next step. The rear end of the drum carries a dial and pointer, so that the water stage may be read directly without looking at the chart. The circuits necessary to connect the Sender and Receiver may consist either of 3 wires or 2 wires and a 298 W. & L. E. GURLEY, TROY, NEW YORK "ground" return. A satisfactory circuit may be obtained by leasing a private telephone line of 2 wires. The current required to operate the receiver is 0.1 ampere and this flows through the line for only a fraction of a second when the contact is made. At all other times the circuits are open. The resistance of the coils is 40 ohms. The power may be supplied by dry cells or storage batteries. For long distances it is better to take it from a 110 volt D. C. power or storage battery line, if continuously available throughout the 24 hours of the day. A lamp placed in the circuit will cut down the current to the proper amount, that is, 0.1 ampere. The power may be connected into the circuit at any point in the line. Any number of Receivers or Indicators may be used on the circuit for one Sender. Blue prints showing the necessary wiring connections will be furnished upon request. THE LONG DISTANCE WATER STAGE INDICATOR answers the purpose where a record of the water level is not desired but only an indication of the level at some distant point. This operates with the same Sender and circuits described above for the Long Distance Graphic Water Stage Register. Instead of the No. 633 Register, a large dial 1 2 inches in diameter, with a moving pointer, is operated by electro-magnets and a ratchet wheel, in the same manner as the Long Distance Register. This dial shows the height of the water at the distant gage HYDRAULIC ENGINEERING INSTRUMENTS 299 house, at any instant. A larger dial can be furnished if desired. Prices, which depend upon the size, will be quoted upon application. FIG. 116 No. 638 FLOAT OPERATED SENDER, FOR LONG DISTANCE GRAPHIC REGISTER This Indicator may also be put on the same circuit with a Register. In many cases it will be desirable to have an Indicator in the power plant for the information 300 W. & L. E. GURLEY, TROY, NEW YORK of the operator, while the Register may be placed in the office of the chief engineer, where the records will be kept and studied. Detailed information concerning the solution ol special gaging problems of hydraulic engineers will be furnished upon request. FIG. 117 No. 639 LONG DISTANCE INDICATOR WITH 12" DIAL INDICATING GAGE No. 639-A will be found a great help in the checking of gage heights in stilling wells in which automatic recording gages are installed. It can be used also wherever water levels are to be observed. This instrument is designed to replace the ordinary hook, chain and staff gages where very accurate readings are required. The sprocket wheel is one foot in cir- HYDRAULIC ENGINEERING INSTRUMENTS 301 cumference and is divided into 100 parts, and the feet may be read on the counter up to 100. This gage will be furnished with or without the float. FIG. 118 No. 639-A INDICATING GAGE 302 W. & L. E. GURLEY, TROY, NEW YORK PRECISION BALANCE THE GURLEY PRECISION BALANCE is the highest development of a weighing instrument and is constructed strictly in accordance with the best scientific principles, all parts being of a sufficient strength to support an overload of 100% without perceptible strain. The capacity of the balance is fifty pounds or twenty- five kilograms in each pan, with a sensibility of one grain or .06 gram at full load. The beam is of a special aluminum alloy which will remain constant under all conditions, and is equipped with a vertically adjust- able weight by which the sensibility reciprocal can be altered to suit the convenience of the operator. The pillar is of bronze with positive beam and pan arrest- ment and with pointer swinging inside of the pillar over a horizontal scale, back of which is placed a mirror to facilitate the readings. All bearings are made of agate and the knife edges are of the best hardened steel. The pan hangers are of bronze and aluminum, and the pans are of nickel plated brass. The base is of highly pol- ished oak or mahogany, with attached spirit level and four leveling screws. The base is about 40 inches long and 15 inches wide. The overall height of the Balance is about 40 inches. In addition to the balance illustrated above, we also manufacture Precision Weights and Measures used as PRECISION BALANCE 303 official standards. These are of the highest degree of accuracy, and are guaranteed to conform to the specifi- cations of the National Bureau of Standards. A certifi- cate of test from this bureau will be furnished when desired. FIG. 119 No. 9570 PRECISION BALANCE 304 W. & L. E. GURLEY, TROY, NEW YORK We have made official weights and measures for the Bureau of Standards and for practically all of the De- partments of Weights and Measures in this country; also for China, the Philippine Islands, Porto Rico and Haiti. We are prepared to furnish weights and measures to conform to the standards of any foreign country. A bulletin describing the weights, measures, and Sealer's equipment will be sent upon request. GENERAL INFORMATION 305 GENERAL INFORMATION EXTENT OF OUR BUSINESS FOR many years our facilities for the manufacture of Engineering and Surveying Instruments have been far superior to those of any other similar establish- ment in the world. They are being constantly increased by the introduction of new machinery and tools. We make in our own factory the lenses for the tele- scopes of our instruments, the platinum filament for the cross wires and stadia wires, the glass vials for the levels, the wooden boxes in which the instruments are carried, the leather cases and straps for these boxes, as well as the castings and all other metal parts of the instruments themselves. Thousands of our instruments have been distributed to all parts of the United States, Canada, Mexico, Cen- tral America, West Indies, South America, China, Japan, Australia, Africa, India and other foreign countries. OUR GUARANTEE All instruments of our own make are examined and tested before being shipped, and are sent to the pur- chaser adjusted, ready for immediate use. They are warranted correct in all their parts we agreeing in the event of any original defect appearing after reason- able use, to repair or replace with new and perfect 306 W. & L. E. GURLEY, TROY, NEW YORK instruments, promptly at our own cost, express charges included; or we will refund the money and the express charges paid by the purchaser. It sometimes happens in a business as large and widely extended as ours that instruments reach our customers in bad condition, owing to careless transporta- tion, or to defects escaping the closest scrutiny of our inspectors. We consider the retention of such instru- ments by the purchaser an injury very much greater to us than to himself. We also consider that a sale is not completed until the purchaser is satisfied in every detail. TRIAL OF INSTRUMENTS If requested to do so, we will ship to the express station nearest the person giving the order and will in- struct the express agent to collect the amount of our bill and hold the money three days. This will give the purchaser an opportunity to test the instrument in the field and if it is not found as represented, he may return it to the express agent who will refund the full amount paid, including transportation charges. This privilege of trial applies only to our large instruments such as Transits, Levels, Compasses, etc., is not given unless requested, and is allowed only in the United States. Privilege of trial is not allowed by the Great Northern or Southern Express Companies. All express companies, however, will allow examination of instruments at their offices, if the shipper requests it for the purchaser. GENERAL INFORMATION 307 ORDERING In ordering always give the Catalogue Numbers of the instruments and accessories selected. If full particulars concerning each item accompany the order, delay will often be avoided, as it will proba- bly be unnecessary for us to write you. If no shipping directions are given, we will always ship by the quickest and safest method. When any articles can be sent safely by mail, we have printed the approximate cost of postage so that, by re- mitting with the order the cost of the article and the postage, the goods can be sent at small expense. Should the amount sent exceed the actual postage, the balance will be returned. All articles can be insured at an extra cost which varies according to the value of the package. For de- tails see Parcel Post Regulations. PACKING AND DELIVERY Each of our Transits, Levels and Surveyors Com- passes is packed in a well finished mahogany case, furnished with lock and key, and leather strap for convenience in carrying. When sent to the purchaser the mahogany cases are carefully enclosed in outside packing boxes of pine, made a little larger on all sides to receive elastic packing material. 308 W. & L. E. GURLEY, TROY, NEW YORK We make no charge for packing boxes or packing, and our instruments are delivered F. O. B. Troy, N. Y., to the express company or freight house. Charges for transportation are in all cases to be paid by the purchaser, we guaranteeing the safe arrival of our goods at the destination indicated at the time of ship- ment. TERMS OF PAYMENT Terms of payment are uniformly cash, and we have but one price, whether ordered in person or by mail. Our prices are as low as instruments of first quality can be made. Remittances may be made by a cashier's bank draft, payable to our order, or by Express Company or Post Office money order payable at Troy, N. Y. These may be sent by mail with the order for the instrument, and if lost or stolen on the route can be replaced by a dupli- cate, and without additional cost. The customer may also send the money in advance by registered mail, or by the express agent, or instruct us to forward the shipment C. O. D. Goods ordered for shipment to foreign countries must be paid for in ad- vance of shipment. Customers ordering instruments and desiring changes in construction from our regular patterns, must make a payment in advance when ordering of fifty per cent, of the price. GENERAL INFORMATION 309 INSTRUMENTS FOR FOREIGN COUNTRIES FIG. 120 Instruments packed for foreign shipment which are to have ocean passage are wrapped in waterproof mater- ial and enclosed in strong packing boxes which are strengthened and protected by special band wire. The cash for all orders for foreign shipments by steamship must, in every case, accompany the order; and if it is desired that we attend to the shipment of the instruments, the remittance must be made ten per cent, more than the catalogue price of the instruments if the order amounts to $250 or less; or eight per cent, more than catalogue price if the order amounts to from $300 to $500; or six per cent, more than catalogue price if the order amounts to from $600 to $1,000. 310 W. & L. E. GURLEY, TROY, NEW YORK This extra remittance is to cover cost of shipping charges, freight and insurance, which must always be paid in advance on all shipments except those consigned to Canada and some parts of Mexico. If the amount remitted is more than enough to cover these expenses, the balance will be returned to the pur- chaser with the receipted bill and bill of lading, unless we are directed to hold it to his credit. Remittances must be made by bank draft on New York City or London, England, and such drafts can be purchased in any of the large cities of the different countries. Our registered cable address is "GURLEY, TROY." Use Bentley's, Western Union, A. B. C. Fifth Edition, or Lieber's Codes. See Private Cable Code on pages 315 to 323. REPAIR OF INSTRUMENTS Each year we receive hundreds of instruments of our own and other makes sent to us for refitting and repairs. We advise our customers who have instruments in need of repairs to send them directly to us, as our facil- ities enable us to do the work economically and promptly. They should always be placed in their own boxes, and then enclosed in an outside packing case, at least an inch larger in all its dimensions, and the space be- tween the two filled with paper wadding, hay or shavings. GENERAL INFORMATION 311 The owner's name and address should always appear on the package and a note specifying the repairs needed should accompany the instrument. A letter should also be sent by mail to us, giving not only directions as to the repairs, but also stating when the return of the instru- ment is required, and the precise location to which it should be forwarded. It should also be remembered that each instrument is made to fit its own spindle, and no other ; and there- fore the leveling head complete (centers and spindle) should always be sent with it. The tripod legs and brass head in which they are inserted need not be sent unless in need of repairs. When requested to do so, we will furnish an estimate of the cost of the repairs on any instrument sent us, before beginning the work. SELECTION OF INSTRUMENTS For ordinary land surveying, the Vernier Compass is required where the variation of the needle is to be allowed, as in retracing the lines of an old survey, etc. When, in addition to the variation of the needle, local attraction must be taken into account and angles taken independently of the needle, an instrument with a graduated limb must be used, and for this purpose a Compass with horizontal limb is required. See No. 294. For municipal engineering, railroad and highway construction, bridge building, drainage and irrigation work, selection should be made from our Precise Tran- 312 W. & L. E. GURLEY, TROY, NEW YORK sits Nos. 6-A to 10- A, 26-A to 29-A, Light Mountain Transits Nos. 26 to 29; and Engineers Wye Levels Nos. 375 to 378. The Light Mountain Transits (regular and Precise types) are also ideal instruments for surveys of mining claims, especially in high elevations, and for surveys of mines in general. For United States Public Land Surveys an instru- ment with the Solar Attachment is required and the Solar Transit is used; see Nos. 30- A, 32-A and 23-A. No. 18-A "Hell Gate Model" Precise Transit is capable of executing triangulation surveys demanding the highest degree of accuracy and refinement. The various Plane Table Outfits have a recognized utility for topographical surveys and map drawing. The Current Meters are almost indispensable in measuring the velocity of the flow of water in harbors, rivers, small streams and irrigation ditches. The Automatic Water Stage Registers are used for determining the variations in the height or stage of the water in connection with water power development, irri- gation investigations and sewage discharge. The Hook Gage is utilized for ascertaining the depth of water flowing over weirs, etc. The Architects Level is employed in laying out buildings, determining the level of their floors, sills and windows, and in the general work of the builder and contractor. GENERAL INFORMATION 313 The Explorers Transit, the Reconnoissance Transit, the Explorers Level and the various forms of Pocket Compasses are designed for preliminary surveys where extreme lightness and portability are required. When iron ores are to be traced, the Dip Compass and the Dial Compass are used. We do not make any instrument by which veins of gold and silver can be traced, or the presence of these metals detected. EXCHANGING OLD INSTRUMENTS Correspondence is solicited relating to exchanging old instruments of our make for those of the latest patterns. We are constantly making such exchanges to the entire satisfaction of our customers and if the old instru- ments are salable as second-hand, after being rebuilt and refimshed, a liberal allowance is made. INVITATION TO VISIT OUR FACTORY A cordial invitation is extended to our customers to visit our Factory in Troy, N. Y. Opportunities are thus had for examining the various instruments we make and for observing the processes of manufacture. Visitors who call on us are greatly impressed with the size of our establishment and also with the elaborate equipment which is required to produce high grade instruments. 314 W. & L. E. GURLEY, TROY, NEW YORK LITERATURE We publish a variety of attractive bulletins contain- ing special information relative to our products. They will be supplied to our correspondents who express an interest in or a desire for some particular instrument. GURLEY SOLAR EPHEMERIS The Solar Ephemeris is published annually. It is an abridgment of the Nautical Almanac, issued by the United States Government, and contains a Table of Mean Refractions in Declination and Tables of Times of Elongation, Culmination and Azimuths of Polaris. It can be conveniently carried in the vest pocket. A copy will be sent postpaid to any engineer or surveyor, on request. PRIVATE CABLE CODE 315 PRIVATE CABLE CODE CABLE CODE : "GURLEY" Use Bentley's, Western Union, Lieber's; or A. B. C. 5th Edition, Codes Cat. No. 6-A 7-A 8-A 9-A 10-A 10-A-3 18-A 23- A 26-A 27-A 28-A 29-A 30-A 32-A 20-A 21-A 22-A 23-A 24-A 25 26 27 28 29 30 102 103 131 135-B 136 137 138 Description Code Word Precise Transit, Engineers size .......................... Abaab Precise Transit, Engineers size .......................... Ababa Precise Transit, Engineers size .......................... Ababs Precise Transit, Engineers size Precise Transit, Engineers size Precise Transit, with Three-Screw Leveling Head Precise Transit, Hell Gate Model Precise Transit, Mountain size Precise Transit, Mountain Precise Transit, Mountain Precise Transit, Mountain Precise Transit, Mountain Precise Transit, Mountain Abaca Abacy Abagn Abago Abaha Abahi size . . . size .......................... Abahl size .......................... Abahs size .......................... Abaib size .......................... Abaig Precise Transit, with Telescopic Solar ................... Abail Explorers Precise Transit ............................... Abaek Explorers Precise Transit ............................... Abaen Explorers Precise Transit ............................... Abaer Explorers Precise Transit ............................... Abaet Explorers Precise Transit ............................... Abagu Light Mountain or Mine Transit ......................... Atimy Light Mountain or Mine Transit ......................... Atjip Light Mountain or Mine Transit . ......................... Atkir Light Mountain or Mine Transit .......................... Atler Light Mountain or Mine Transit ......................... Atmar Light Mountain or Mine Transit ......................... Atnas Reconnoissance Transit ................................. Avseb Reconnoissance Transit ................................. Abalm Limb I ................ , ................................. Abaip Limb IV ................................................ Abaiy Variation Arc .......................................... Arbuc Vertical Circle .......................................... Arfen Vertical Circle .......................................... Arfid Vertical Circle ......................................... Argog Vertical Circle . . Arins 316 W. & L. E. GURLEY, TROY, NEW YORK Cat. No. Description Code Word 139 Vertical Circle Abajo 139-A Vertical Arc Arkal 139-B Vertical Arc Arkon 140 Vertical Arc Arlik 141 Aluminum Guard Armil 145 Level on Telescope Arnon 146 Reversion Telescope Level Arobs 148 Clamp and Tangent Aroms 149 Beaman Stadia Arc Arpal 149-A Beaman Stadia Arc Abake 149-B Beaman Stadia Arc Abaks 149-C Beaman Stadia Arc Abaku 150 Gradienter Arram 151 Stadia Wires, Adjustable , Abald 152 Stadia Wires, Fixed Abalk 154 Dust Guard Abalo 155 Pinion Movement Abalt 157 Sights on Telescope Arren 158 Sights on Standards Arrot 160 Detachable Side Telescope and Counterpoise Arsan 161 Detachable Riding Telescope Artap 165 Reflector for Transit Cross W r ires Artot 166 Reflector for Level Cross Wires Arvit 167 Elbow Eyepiece Abaly 168 Diagonal Prism Arwet 169 Eyepiece Cap Abalu 170 Plummet Lamp Arzub ISO Attached Magnifier Asbid 181 Attached Microscopes Abamo 182 Attached Microscopes Abams 185 Limb Graduation Ascog 186 Limb Graduation Asdig 187 Vertical Circle Graduation Asels 188 Vertical Circle Graduation Asgle 189 Vertical Circle Graduation Abamu 190 Burt Solar Attachment Ashik 192 Solar Screen Abana 193 Patent Latitude Level Asilt 196 Striding Level Askon 197 Adjusting Bar Abang 226 Vernier Compass Agwen 241 Leveling Adopter Afbir 242 Leveling Head Afcot PRIVATE CABLE CODE 317 Cat. No. Description Code Word 262 Telescopic Sight Apbat 20.") Vertical Circle for No. 262 Telescopic Sight Apfob 266 Level on Telescope for No. 262 Telescopic Sight Aphic 267 Clamp and Tangent for No. 262 Telescopic Sight Aplad 268 Offset Standard and Counterpoise for No. 262 Telescopic Sight Apost 285 Pocket Compass with Limb Addip 294 Compass with Limb and Telescope Abans 300 Pocket Vernier Compass Afrad 305 Pocket Vernier Compass' Afseg 325 Clamp and Tangent Agbet 326 Rack and Pinion Movement Agcat 327 Leveling Adopter Agdix 328 Leveling Head Agern 835 Geologists Compass Afnid 341 Dip Compass Afkob 341-A Dip Compass Aflam 350 Dial Compass Afirl 375 Engineers Wye Level Akary 377 Engineers Wye Level Akdul 378 Engineers Wye Level Akgun 381 Architects Level Ajrot 384 Explorers Level Abaoh 400 Transit Tripod Axnig 401 Transit Tripod Axots 405 Transit Tripod Axrul 406 Transit Tripod Axtil 410 Transit Tripod Axvim 411 Transit Tripod Axyan 412 Transit Tripod Abaok 415 Compass Tripod Awact 41 6 Compass Tripod Awder 420 Compass Tripod Awflt 421 Compass Tripod Awify 425 Compass Tripod Aworl 426 Compass Tripod Awrif 430 Level Tripod Axbar 431 Level Tripod Axcet 435 Level Tripod Axdox 436 Level Tripod Axfoy 440 Level Tripod Axgub 441 Level Tripod Axhob 443 Level Tripod Abapa 318 W. & L. E. GURLEY, TROY, NEW YORK Cat. No. Description ('ode Word 450 Plain Plummet .... Abaph 452 Plain Plummet Abapt 454 Plain Plummet Abapy 456 Plain Plummet Abarb 458 Plain Plummet Abarc 460 Plain Plummet Abarf 465 Adjustable Plummet Abari 471 Iron Spads Abarm 472 Stake Tacks Vbarp 473 Stake Tacks Abars 474 Plummet Cord Abaso 475 Leather Case Abasp 476 Leather Case Abast 478 Leather Case Abasy 479 Leather Case Abata 480 Leather Case Abath 485 Leather Case Abaty 486 Leather Case Abaud 487 Leather Case Abaur 490 Leather Pouch Abaux 491 Leather Pouch Abauz 492 Leather Pouch Abauj 494 Tripod Case Abava 496 Tripod Case Abavi 497 Tripod Case Abavy 498 Leather Field Bag Abawi If metric graduations are wanted, specify "METRIC" after the code word for the Red. 500 Philadelphia Rod Albol 500-A Philadelphia Rod Abaxo 500-B Philadelphia Rod Alcun 500-R Service Rod Abayu 501 Philadelphia Rod Aldon 501 -B Special Self-Reading Rod Alfop 502-A Philadelphia Mining Rod Algor 504 Troy Rod Alimb 505 New York Rod Aljer 510 Architects Rod Alnew 511 Architects Rod Alond 513 Telemeter Rod Alrob 514 Telemeter Rod Alsay 514-B Stadia Rod Abaye 514-C Stadia Rod Abayr 514-D Stadia Rod Abayt PRIVATE CABLE CODE 319 Cat. No. Description Code Word 514-E Stadia Rod Abaza 515 Telescopic Rod Altic 510 Cross Section Rod Alubs 517 Slip-Jointed Rod Abbej 518-A Plain Rod Alvof 518-B Plain Rod Alwed 519-A Plain Rod Amand 519-B Plain Rod Ambin 520-A Plain Rod Amcus 520-B Plain Rod , Amdut 521-B Plain Rod Amfis 522-A Plain Rod Amgit 522-B Plain Rod Amhow 522-C Plain Rod Amild 524-A Plain Rod, 4 ply Amkoy 525-B Flexible or Pocket Leveling Rod Ampod 52G-A Flexible or Pocket Leveling Rod Amrid 52G-B Flexible or Pocket Leveling Rod Amsed 527 Flexible or Pocket Leveling Rod Am tad 528 Flexible or Pocket Leveling Rod Amudy 530 Combined Leveling Pole and Flagstaff Akhon 531 Combined Leveling Pole and Flagstaff Akkip 534 Wood Flagstaff Abazi 535 Wood Flagstaff Abazy 53G Wood Flagstaff Abbac 537-A Screw-Jointed Wood Flagstaff Abbaf 537-B Screw-Jointed Wood Flagstaff Abbal 537-C Screw- Jointed Wood Flagstaff Abbam 537-D Screw-Jointed Wood Flagstaff Abbap 538- A Screw-Jointed Wood Flagstaff Abbas 538-B Screw-Jointed Wood Flagstaff Abbaw 540-A Steel Ranging Pole Abbed 540-B Steel Ranging Pole Abbeh 541 Iron Tubnlar Ranging Pole Abbek 543 Iron Tubular Ranging Pole Abben 544 Iron Tubular Ranging Pole Abbet 550-R Gurley Precise Rod Abbig 551-R Molitor Precise Rod Abbif 552-R Tape Leveling Rod Abbic 545 Rod Level Amnez 546 Rod Level Amnit 547 Rod Level Amnor 548 Rod Level Abbev 570 Johnson Plane Table Movement Abbil 570-A Johnson Plane Table Movement Abbim 320 W. & L. E. GURLEY, TROY, NEW YORK Cat. No. Description Code Word 571 Johnson Plane Table Movement Abbip 573 Drawing Board Abbis 573-A Drawing Board Abbiy 573-B Drawing Board Abboh 573-T Drawing Board Abbot 573-X Drawing Board Abbok 574 Plumbing Arm and Plummet Abbon 575 Combined Compass and Levels Abbor 57G-B Plane Table Outfit Abboz 576-C Plane Table Outfit Abbud 584-B Telescopic Alidade Abnot 584-C Telescopic Alidade Abbuk 585 Box Compass Abome 586 Traverse Plane Table Outfit Ankud 587 Traverse Plane Table Movement and Drawing Board Anlic 588 Box Compass Anmid 589 Ruler Sight Alidade Anoby 590-A Pocket Sight Alidade Anpad 590-B Pocket Sight Alidade Anruk 592-C Explorers Alidade Abcag 592-D Explorers Plane Table Outfit Abcal 592-F Explorers Plane Table Outfit Abeam 592-H Explorers Plane Table Outfit Abcap 594 Army Sketching Case Abcas 596 Fiala Scout Sketching Case Abced 609 Electric Register for Current Meters Acrub 616 Current Meter Acvod 617 Current Meter Acwid 619 Time Recorder or Stop Watch Adaf t 621 Current Meter Adbel 623 Current Meter Adbot 628 Hook Gage Abcek 630 Printing Water Stage Register Anvel 632 Tape Reel Anwat 633 Graphic Water Stage Register Abcet 634 Graphic Water Stage Register Abcev 634-A Graphic Water Stage Register Abcic 636 Graphic Water Stage Register Abcif 637 Long Distance Register Abeik 638 Long Distance Sender Abeil 639 Long Distance Indicator Abein 639-A Indicating Gage Abeir 640 Monocular Hand Level Aklut 643 Locke Hand Level Akpow 646 Abney Hand Level Aksoy PRIVATE CABLE CODE 321 Cat. No. Description Code Word G46-A Abney Hand Level Abcil 647 Abney Hand Level Abcim 647-A Abney Hand Level Abcip 648 Abney Hand Level Abcuv 649 Stadia Hand Level Aktye 650 Iron Chain Abcis 631 Iron Chain Abciy 652 Iron Chain Abcod 653 Iron Chain Abcob 656 Steel Chain '. Abcok 658 Steel Chain Abcon 662 Steel Chain Abcox 670 Brazed Steel Chain Abpit 671 Brazed Steel Chain Abret 672 Brazed Steel Chain Absat 673 Brazed Steel Chain Abtoy 690 Vara Chain Abcur 691 Vara Chain About 694 Vara Chain Abcux 695 Vara Chain Abcyb 700 Vara Chain Abcyc 704 Vara Chain Abcyf 708 Vara Chain Abcyg 710 Vara Chain Abcyl 715 Meter Chain Acbul 719 Meter Chain Acfon 723 Meter Chain Acily 730 Meter Chain Acker 732 Meter Chain Aclar 740 Marking Pins Abcym 742 Marking Pins Abcys 743 Marking Pins Abdah 744 Marking Pins Abdan 748 Marking Pins Abdat 749 Marking Pin Carrying Ring Abdav 750 Timber Scribe Abdax 774 Steel Ribbon Chain Tape Abdaz 775 Steel Ribbon Chain Tape Abdeb 776 Steel Ribbon Chain Tape Abdec 777 Steel Ribbon Chain Tape Abdef 778 Steel Ribbon Chain Tape Abdeg 779 Steel Ribbon Chain Tape Abdep M-20 Metric Steel Ribbon Chain Tape Abdes M-25 Metric Steel Ribbon Chain Tape Anper M-30 Metric Steel Ribbon Chain Tape Anrot 322 W. & L. E. GURLEY, TROY, NEW YORK Cat. No. Description Code Word M-50 Metric Steel Ribbon Chain Tape An sub M-100 Metric Steel Ribbon Chain Tape Antic V-20 Vara Steel Ribbon Chain Tape Abdew V-30 Vara Steel Ribbon Chain Tape Abdid V-50 Vara Steel Ribbon Chain Tape Abdik V-100 Vara Steel Ribbon Chain Tape Abdin 780 Metallic Tape Abdir 782 Metallic Tape Abdit 783 Metallic Tape Abdix 786 Metallic Tape Abdob 790 Metallic Tape without Case Abdoc 791 Metallic Tape without Case , Abdof 792 Metallic Tape without Case ^. . . . . . Abdog 794 Metallic Tape without Case Abdol 795 Reliable Steel Tape Abdom 796 Reliable Steel Tape Abdop 797 Reliable Steel Tape Abdos 798 Reliable Steel Tape Abduc 799 Reliable Steel Tape Abduf 800 Reliable Junior Steel Tape Abdug 801 Reliable Junior Steel Tape Abdul 808 Rival Steel Tape Abdum 809 Rival Steel Tape Abdup 810 Rival Steel Tape Abdus 811 Rival Steel Tape Abduy 812 Rival Steel Tape Abdye 813 Rival Steel Tape Abdyk 814 Wolverine Steel Tape Abdyr 815 "Wolverine Steel Tape Abdyt 816 Wolverine Steel Tape Abdyu 817 Wolverine Steel Tape Abead 820 Engineers Steel Tape Abeah 821 Engineers Steel Tape Abeaj 822 Engineers Steel Tape Abeak 823 Engineers Steel Tape Abean 824 Engineers Steel Tape Abear 831 Engineers Steel Tape Abeat 832 Engineers Steel Tape Abeax 833 Engineers Steel Tape Abebe 834 Engineers Steel Tape Abebo 835 Engineers Steel Tape Abebu 841 Steel Tape Handles Abech 842 Steel Tape Handles Abeco 844 Spring Balance for Tapes Abect 846 Steel Tape Clamp Handles Abeda PRIVATE CABLE CODE 323 Cat. No. Description Code Word 849 String Level Abeds 850 Extra Wide Steel Tape Abedy 851 Extra Wide Steel Tape Abeeb 852 Extra Wide Steel Tape Abeec 853 Extra Wide Steel Tape Abdiz 854-A Extra Wide Steel Tape Abeef 854-B Extra Wide Steel Tape Abeeg 860 Pocket Steel Tape Abeel 863 Pocket Steel Tape Abeem 866 Pocket Steel Tape Abeep 870 Pocket Steel Tape Abees 873 Pocket Steel Tape Abefa 875 Pocket Steel Tape Abefi 877 Pocket Steel Tape Abefs 879 Pocket Steel Tape Abefy 885 Punch and Riveter Abega 886 Extra Eyelets Abegi 887 Eureka Tape Outfit Abegs 3153 Wood Box Pocket Compass Abegy 3154 Wood Box Pocket Compass Abehe 3155 Wood Box Pocket Compass Abeho 3215 Brunton Pocket Transit . Abeht 324 RENSSELAER POLYTECHNIC INSTITUTE RENSSELAER POLYTECHNIC INSTITUTE TROY, NEW YORK A School of Engineering and Science RECORD. Founded in 1824, the Institute is the oldest school of Science and Engineering, having a con- tinuous existence, to be established in any English speaking country. Students have come to it from all the States and Territories of the Union and from more than thirty foreign countries. Its graduates have be- come distinguished in the practice of their profession all over the civilized world. UNDERGRADUATE COURSES Courses in Civil, Mechan- ical, Electrical and Chemical Engineering and in General Science, each four years in duration, leading to the degrees Civil Engineer (C. E.), Mechanical Engineer (M. E.), Electrical Engineer (E. E.), Chemical Engin- eer (Ch. E.), and Bachelor of Science (B. S.) are now given, as well as special courses in Chemistry, Water Analysis, Drawing, Surveying Theory and Practice, Railroad Engineering Theory and Practice, Joinery and Pattern Making, Machine Shop Practice, and in various branches of Theoretical and Applied Engineering, in- cluding work in the Chemical, Physical, Mechanical, Electrical and Materials Testing Laboratories. GRADUATE COURSES Graduate courses leading to Masters' degrees in the five subdivisions given as under- graduate courses are also provided. These are each one RENSSELAER POLYTECHNIC INSTITUTE 325 year in duration and lead to the degrees M. C. E., M. M. E., M. E. E., M. Ch. E., and M. S. Graduate courses in various branches of science and engineering, each three years in duration, leading to the degrees Doctor of Philosophy, Ph. D., Doctor of Science, Sc. D., and Doctor of Engineering, D. Eng., are also given. BUILDINGS Most of the buildings of the Institute are situated on a plot of ground, containing about twenty-three and one-half acres, extending from Eighth Street eighteen hundred feet easterly to Fifteenth Street. The Carnegie Building, Proudfit Laboratory, Walker Laboratory, Russell Sage Laboratory, Pittsburgh Admin- istration Building and Library, '87 Gymnasium, White Dormitory, Hunt Dormitory, Campus Dormitory, Rus- sell Sage Dining Hall, Central Heating and Power Plant, and Rensselaer Union Club House are situated upon it. The Machine Shop and old Gymnasium are situated upon adjacent plots. The Athletic Field is beside the Club House on the main plot. APPARATUS The chemical, physical, electrical, me- chanical and testing laboratories are completely equipped with the most modern machines and apparatus. These include many forms of steam engines and turbines, gas and oil engines, pumps, water wheels and turbines, elec- trical generators and motors, powerful machines for testing the strength of metals, wood, stone, brick, etc., as well as full collections of apparatus for work in all the laboratories and a complete assortment of surveying instruments for field work. 326 RENSSELAER POLYTECHNIC INSTITUTE INSTRUCTION Instruction is given in the design and construction of roads, railroads, bridges, arches, roofs, water works, sewers, canals, river improvements, tunnels, foundations, boilers, steam engines, steam turbines, gas engines, ships, pumps, water wheels, heating and refrig- erating apparatus, electric machinery, dynamos and telephone and electric lighting systems. Instruction is also given in chemical analysis, electro-chemistry, assay- ing, metallurgy, mineralogy and geology. PHYSICAL CULTURE Lectures on hygiene are given and a large modern gymnasium and an athletic field, with a competent corps of instructors, provide oppor- tunity for athletic exercise necessary for the health of the students. OTHER STUDENT ACTIVITIES Quarters for the Band, Glee Club, and other Musical Clubs, publications and other student activities are provided in the Club House, controlled by a Student Committee. EXPENSES The tuition for undergraduate courses is either $250 or $260 a year, depending upon the course taken, and that for graduate courses is $150 a year. Board and furnished lodgings, either in the Institute Dining Hall and Dormitories or in private houses, may be obtained at a cost, for both, of from about $7 to $10 a week. . / , OTHER INFORMATION For Catalogues and other pamphlets giving full information apply to the Director of Rensselaer Polytechnic Institute, Troy, N. Y. TABLE OF CONTENTS 327 TABLE OF CONTENTS Page Abney Level and Clinometer 203-204 Acoustic Current Meters 276, 277, 278 Adjustable Stadia Wires 29 Adjusting or Striding Level 122, 123, 124 Adjustment of Architects Level 188, 189 Engineers Y Level 181-187, 189-195 Line of Collimation 77-79, 190-191, 256 Objective Slide 80-81 Solar Attachment , 114-122, 139-144 Surveyors Compass 154-157 Telescopic Alidades 255, 256 Telescopic Sight 163-165 Transits 76-83 Alidades for Plane Tables 246-250, 259 Aluminum Instruments and Accessories 85, 177-179 Arc, Vertical, for Transits 88 Architects Levels 188, 189 Army Sketching Cases 260-263 Astronomical Terms 107-113 Attachments and Extras for Compasses 157-163 Levels 185 Transits 83-106 Ball Spindle 151, 157 Battery for Current Meters 282 Beaman Stadia Arc 29, 40, 74, 84, 90-96, 119, 248-249 Boxes and Cases for Instruments 307, 308, 309 Branch Sales Office 313 Balance, Precision 302, 303 Cable Code 315-323 Cases for Instruments 58, 59, 307, 308, 309 Centers of Transits 32 Centers of Levels 187 Center Pin , 156, 157 Chains 268-271 Metric and Vara 268, 271 Chain Tapes 268, 269 Circle, Vertical, for Transits 85-87 Clamp and Tangent 31, 32, 41 Clinometers 203, 204 Collimation, Adjustment of Line of 77-79, 190, 191, 256 Compass Attachments for Levels 185 Compass Circle and Compass Box of Transits 33, 34 328 W. & L. E. GURLEY, TROY, NEW YORK Page Compasses, Surveyors, Attachments and Extras 145-180 Compass Attachments for Levels 185 Dial 176-179 Geologists 170-172 Miners Dip Needle 173-175 Plain 146 Pocket 168-180 Pocket Vernier 180-A, 180-B Telescope 166, 167 Use of, Adjustments and Repairs 152-157 Vernier 146, 152 Wood Box 179, 180 Constant for Stadia Wires 70-75 Cross Wires 28, 29 Cross Wire Reflectors 102, 103 Meters 274-282 Declination Arc 114-140 of Magnetic Needle 34, 35, 146 of the Sun 108, 132, 134 Tables 127-134 Detachable Telescopes for Transits 101, 102 Diagonal Prism for Eyepiece of Telescopes 103, 104 Dial Compasses 176-179 Dip Needle Compasses 173-175 Disappearing Stadia Wires 29 Diurnal Variation 149 Dust Guard for Objective Slide of Telescope 26, 184 Electric Current Meters 276, 278-280 Register 281, 282 Electricity 153 Engineers Levels 181-187 Ephemeris, Solar 126-314 Explorers Alidades 249, 250 Levels 196, 197 Transits, Precise 56, 57 Extras for Compasses 157-163 for Levels 185 for Transits .-. 83-106 Exchanging Old Instruments 313 Eyepiece for Transit Telescopes 26, 27 Field Bags See No. 498 in Price List. Figuring of Horizontal Limbs 35-38 Fixed Stadia Wires 28, 29 Flagstaffs or Ranging Poles 230-232 TABLE OF CONTENTS 329 Page Foreign Shipments 309, 310 Forest Service Compass 170-172 Gage, Metal Hook '. 283-285 General Information 305-314 Geologists Compass 170-172 Grades, Attachment for establishing 99,100 Gradienter 96-100 Graduations of Limb and Vertical Circle 35-38 Guard, Aluminum or Bronze 85-87 Guarantee 305 Hand Levels 202-205 Hell Gate Bridge, Erection of 46-48 Hook Gage, Metal 283-285 Hour Circle and Hour Arc 114, 124, 141, 179 Hydraulic Engineering Instruments 274-301 Illustrations, List of 15-20 Index (Table of Contents) , 327-336 Information, General , 305-314 Instructions for Using Transits . . . , , 68, 69 Instruments, Selection of 311-313 Exchanging Old 313 Inverting Eyepiece 26, 27 Invitation to Visit Factory 43, 313 Johnson Plane Table Movement 244-250 Jointed Leveling and Stadia Rods and Sight Rods 217-219, 221, 231, 232 Latitude Arc 115, 116 Level 105 Leather Cases and Pouches 59 Level Attachments for Transits 35, 89, 90 Striding 123, 124 on Telescope 89, 90 Vials and Spirit Levels 35, 66, 76, 77, 149, 154, 186, 191, 192 Leveling Adopter 157, 158 Head 42, 52, 157, 159, 187 Head, 3 screw , 52 Instruments, Architects 188, 189 Instruments, Engineers Y 181-187 Instruments, Explorers 196, 197 Poles 231, 232 Rods and Poles 206-232 Screws 42 330 W. & L. E. GURLEY, TROY, NEW YORK Page Levels, Adjustment of 189-201 Attachments for 185 Hand 202-205 Use of 198-201 Light Mountain Transits 54, 55 Limbs of Compasses 169 of Transits 32, 35-38 Line of Collimation 77-79, 190, 191, 256 List of Illustrations 15-20 Literature 314 Locke Hand Level 202 Magnetic Declination 146-148 Needle 34, 35, 146 Magnifiers 49, 106 Magnifying Power of Telescope 27 Marking Pins 271 Metallic Tapes 269 Meter Chains 268 Meters, Current 275-282 Miners Dip Needle Compasses , , 173-175 Mining Transits 44, 55, 57, 102 Monocular Hand Level 204, 205 Mountain Transits 54, 55 Needles 34, 66, 146-149, 154, 155 Objective of Telescopes 23 Slide of Telescopes 66, 185, 186, 194, 195 Offset Standard 161, 162 One Piece Truss Standard 30 Optical Axis 25, 161 Principle of Telescope 23-25 Ordering 307 Outkeeper 149 Packing and Delivery 307-309 Parts of Instruments liable to injury, Prices of See Price List. Payment, Terms of 308 Pins, Marking . . . .' 271 Plain Compasses 146 Compasses, Pocket 168, 169 Plane Tables 243-259 and Alidades, Use and Adjustment of 250-256 Traverse 257-259 Plates of Transits 32, 33 TABLE OF CONTENTS 331 Page Platinum Cross Wires 28,29 Stadia Wires 28, 29, 69-75 Plumbing Arm 243 Plummet Cord See Price List. Lamp 104 Plummets 272, 273 Pocket Compasses 168, 169 Leveling Rods 206-232 Polar Axis 122 Poles, Jointed and Ranging 231, 232 Power of Telescopes 27 Price List See pocket inside of back cover. Prismatic Eye Piece for Transits and Telescopic Alidades 103, 104 Railroad Compasses, Pocket 168, 169 Ranging Poles , 231, 232 Reconnoissance Transits 60, 61 Reflectors for Cross Wires and Limb of Transits 40, 102, 103 Refractions 125, 126 Table of 127, 131 Remittance 308 Rensselaer Polytechnic Institute 324-326 Repairs to Instruments 67, 83, 310, 311 Riding or Top Telescopes 101, 102 Rod Levels 233-236 Rods and Poles, Leveling, Stadia and Sight 206-232 Rods, Flexible or Pocket 229 Metric 230 Precise 224-228 Repairs to 237 Tape , 225, 226 Selection of Instruments 311-313 Shifting Center for Leveling Head of Transits 42 Short Focus 184, 185 Side Telescope 101, 102 Sketching Cases, Army - 260-263 Sketching Case, Fiala Scout 264-267 Smith Army Sketching Case : : . . . 260-263 Sockets of Levels .-.- 187 of Transits 41, 42 Solar Attachment for Transits 114-144 Ephemeris 126, 314 Screen 106 Transits 119, 138 332 W. & L. E. GURLEY, TROY, NEW YORK Page Spirit Levels and Level Vials 35, 66, 76, 77, 149, 154, 186, 191, 192 Stadia Arc, Beaman 90-96 Constant 70-75 Stadia Rods 218-220 Surveying 69-75 Wires, Platinum 28, 29, 69-75 Staff Mountings 151 Standards 30, 31 Steel Tapes 269, 270 Stop Watch or Time Recorder for Current Meters See Price List. Striding Level 123, 124 Surveyors Chains 268 Tables. Declination _ 127-134 Plane . , 243-259 Tangent Scale on Sight Vanes 150 Tape Lines, Metallic 269 Lines, Steel 269, 270 Targets, Special, for Leveling Rods 237 Telegraph Codes , 315-323 Telescope, How composed 23-29 for Vertical Sighting, Detachable or Extra 101, 102 Telescopic Sight Attachment 158-165 Sight, Adjustments of 163-165 Solar Attachment 136, 137 Terms of Payment .'. . - 308-310 Three Screw Leveling Head 52 Top or Riding Telescope 101, 102 Transit Instruments, General Description 23-75 Transits, Adjustment of 76-144 Care of 62-67 Use of 68-75 Attachments for 83-144 Distinctive Features of 44 Selection of 45 Explorers Precise 56-59 Hell Gate 49 Light Mountain and Mining 54, 55 Precise -. , 44-53 Reconnoissance 60, 61 Solar 119-138 Solar Attachment for 114-144 Transportation 307, 308 Traverse Plane Table Board and Tripod 257-259 Trial of Instruments . 306 TABLE OF CONTENTS 333 Page Tripod Cases 242 Tripods 43, 238-242 Truss Standard, Patented, One Piece 30 Use of Current Meters 275, 276 Compasses 152, 153 Hook Gages 284,285 Levels 198 Transits 68-75 Vara Chains and Tape Lines ; 268, 271 Variation Arc of Transits 32-34 of the Magnetic Needle 34, 35, 146-148 Vernier Compasses 146-152 The Use of 146 Verniers 38-40, 81 Vertical Arc and Vertical Circle 81, 85, 86, 87, 88 Wading Rods for Current Meters 277 Warranty 305, 306 Water Stage Registers 286-301 Weights of Levels See Price List. Transits See Price List. Weights and Measures Equipment 302-304 Wye Levels 181-187 Wyes 186 Y Levels 181-187 Ys of Leveling Instruments 186 RETURN TO the circulation desk of any University of California Library or to the NORTHERN REGIONAL LIBRARY FACILITY Bldg. 400, Richmond Field Station University of California Richmond, CA 94804-4698 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 2-month loans may be renewed by calling (510)642-6753 1 -year loans may be recharged by bringing books to NRLF Renewals and recharges may be made 4 days prior to due date DUE AS STAMPED BELOW SENT ON ILL OCT 23 2003 U. C. BERKELEY DD20 15M 4-02 Price List GURLEY MANUAL Forty-Eighth Edition TROY, N. Y., U. S. A. APRIL, 1921 All prices in this list are in U. S. Currency. State which Edition of Manual when ordering, and give Catalogue number. This Price List supersedes all previous Editions. TRANSITS Price Precise Transits, Engineers Size, with one Piece Truss Standard, 6.25 in. limb, 3Y a in. needle, 11 in. telescope, mahogany box and split leg tripod. No. G-A with clamp and tangent to telescope axis $299.00 No. 7-A with level on telescope and clamp and tangent to telescope axis 318.00 No. 8-A with 6 in. vertical circle, level on telescope and clamp and tangent to telescope axis 346.00 No. 9-A with vertical arc 3 in. radius, level on telescope and clamp and tangent to telescope axis 346.00 No. 10-A with vertical arc 3 in. radius, level on telescope and Gradienter combined with clamp and tan- gent to telescope axis (see page 47) 364.00 No. 10-A-3 like No. 10-A, but with three-screw leveling head (see page 53) No. 18-A Precise Transit, Hell Gate Model, 6.7 in. limb, 3% in. needle, 11 in. telescope, level on tele- scope, clamp and tangent to telescope axis, two vernier vertical circle 5 in. diameter and level on guard; mahogany box and split leg tripod (see page 49) 575.00 Precise Transits, Explorers Size, with One Piece Truss Standard, 4 in. limb, 2.13 in. needle, 6.5 in. telescope, leather covered mahogany box and jointed extension leg tripod. No. 20-A with 4 in. vertical circle, level on telescope and clamp and tangent to telescope axis (see page 57) 315.00 No. 21-A with vertical arc 2 in. radius, level on telescope and clamp and tangent to telescope axis 315.00 No, 22-A with vertical arc 2 in. radius, level on telescope and Gradienter combined with clamp and tan- gent to telescope axis 333.00 No. 23- A like No. 21-A, but with Burt Solar Attachment. . 411.00 No. 24-A like No. 20-A, but with a two vernier vertical circle baying a level attached to the guard... 363.00 &. '.-..W. fr. L, E. GURLEY, TROY, NEW YORK -"- **=< " . -'* Price Precise Transits, Light Mountain Size, with One Piece Truss Standard, 5.65 in. limb, 3 in. needle, 8 in. telescope, mahogany box and ex- tension leg tripod. No. 25 -A with clamp and tangent to telescope axis $293.00 No. 26-A with level on telescope and clamp and tangent to telescope axis 312.00 No. 27-A with 4% in. vertical circle, level on telescope, clamp and tangent to telescope axis (see page 44) :. .. : 340.00 No. 28- A with vertical arc 2.5 in. radius, level on telescope and clamp and tangent to telescope axis 340.00 No. 29-A with vertical arc 2.5 in. radius, level on telescope and Gradienter combined with clamp and tan- gent to telescope axis 358.00 No. 30-A like No. 28-A, but with Burt Solar Attachment (see page 119) 436.00 No. 32-A like No. 27-A, but with Telescopic Solar Attach- ment (see page 138) 515.00 The horizontal limbs of Transits Nos. 6-A to 18-A and Nos. 25-A to 32-A are figured in two rows to 360 each way, reading in opposite directions and known as Limb 4, (see page 37). Light Mountain Transits, 5.65 in. limb, 4 in. needle, 8 in. telescope, mahogany box and ex- tension leg tripod. No. 25 with clamp and tangent to telescope axis 268.00 No, 26 with level on telescope and clamp and tangent to telescope axis 287.00 No. 27 with 4% in. vertical circle, level on telescope and clamp and tangent to telescope axis 315.00 No. 28 with vertical arc 2.5 in. radius, level on telescope and clamp and tangent to telescope axis 315.00 No. 29 with vertical arc 2.5 in. radius, level on teles- cope and Gradienter combined with clamp and tangent to telescope axis No. 30 like No. 28, but with Burt Solar Attachment.... 411.00 Reconnaissance Transits, 5 in. limb, 3% in- needle, 9 in. telescope, mahogany box and exten- sion leg tripod. No. 102 with 4V& in. vertical circle, level on telescope and clamp and tangent to telescope axis (see page 61) 235.00 No. 103 with vertical arc 2.5 in. radius, level on telescope clamp and tangent to telescope axis 244.00 The horizontal limbs of Transits Nos. 20-A to 24-A, Nos. 25 to 30, and Nos. 102 and 103, are figured to 90 each way, inner row, and to 360, outer row, known as Limb 1, (see page 36). W. & L. E. GURLEY, TROY, NEW YORK 3 ATTACHMENTS AND EXTRAS FOR GURLEY TRANSITS The following prices are for attachments only when furnished with a new instrument. When fitted to a completed instrument, the cost of alterations must he added to the price of the new parts. Price No. 131 Variation Arc added to Transits when sent for repairs $25.00 No. 135-B Vertical Circle, 4 in. diameter, with vernier reading to 1 minute 18,00 No. 136 Vertical Circle, 4.5 in. diameter, with vernier reading to 1 minute (see page 85) 18.00 No. 137 Vertical Circle, 5 in. diameter, with vernier reading to 1 minute 22.00 No. 138 Vertical Circle, 5 in. diameter, with two oppo- site double verniers, reading to 1 minute, and with guard (see page 86) 50.00 No. 139 Vertical Circle, 4.5 in. diameter, with gradua- tions on edge or rim, protected by a metal guard. Circle graduated to 30 minutes, with vernier reading to 1 minute (see page 87) . . 45.00 No. 139-A Vertical Arc, 2 in. radius, with vernier reading to 1 minute, movable by tangent screw 28.00 No. 139-B Vertical Arc, 2.5 in. radius, with vernier read- ing to 1 minute, movable by tangent screw. . 28.00 No. 140 Vertical Arc, 3 in. radius, with vernier reading to 1 minute, movable by tangent screw (see page 88) 28.00 No. 141 Detachable Aluminum Guard for Vertical Circle (see page 88) 9.00 No. 145 Level on Telescope, with ground and graduated vial (see page 89) 19.00 No. 146 Level on Telescope, with Reversion Vial (see page 89) 27.00 No. 148 Clamp and Tangent to Telescope Axis (see page 89) 9.00 No. 149 Beaman Stadia Arc, for Transit having a one- vernier vertical circle or vertical arc (see page 40) 22.00 No. 149-A Beaman Stadia Arc, for Transit having a two- vernier vertical circle No. 138 50.00 No. 149-B Beaman Stadia Arc, for Telescopic Alidades Nos. 592 and 592-A 20.00 No. 149-C Beaman Stadia Arc with edge graduations, for Telescopic Alidade No. 584-B 45.00 No. 150 Gradienter, combined with Clamp and Tangent (sea page 96) 27.00 No. 151 Platinum Stadia Wires, adjustable, and dia- phragm 8.00 No. 152 Platinum Stadia Wires, fixed, and diaphragm 10.00 No. 154 Dust Guard to objective slide (see page 26) ... 7.00 No. 155 Pinion movement to eyepiece slide 8.00 No. 157 Sights on Telescope, with folding joints 12.00 No. 158 Sights on Standards, at right angles with teles- cope 12.00 No, 160 Detachable Side Telescope and Counterpoise, for vertical sighting (see page 101) 40.00 No. 161 Detachable Riding Telescope, for vertical sight- ing (see page 101) 40.00 4 W. & L. E. GUBLEY. TROY. NEW YORK Price No. 165 Reflector for illuminating cross wires (see page 103) $12.00 No. 166 Reflector for illuminating cross wires of large Wye Level (see page 103) 15.00 The elliptical reflecting pieces on Reflectors Nos. 165 and 166 are of sterling silver. No. 167 Elbow Eyepiece, in addition to regular eyepiece, and interchangeable 50.00 No. 168 Diagonal Prism for eyepiece of telescope (see page 103) 12.00 No. 169 Eyepiece Cap with darkener glass in shutter, for direct solar observations 3.00 No. 170 Plummet Lamp for mine surveying (see page 104) 15.00 No. 180 Attached Magnifier, with three universal joints, to read verniers (see page 106) each 8.00 No. 181 Attached Microscopes to read verniers of hori- zontal limb, as shown with No. 18-A Transit (see page 106) per pair 30.00 No. 182 Attached Microscopes to read verniers of No. 138 vertical limb, as shown with No. 18-A Transit (see page 106) per pair 30.00 No. 185 Graduation of horizontal limb to read to 20 or 30 seconds, extra 15.00 No. 186 Graduation of horizontal limb to read to 10 seconds, extra 35.00 No. 187 Graduation of 4.5 or 5 in. Vertical Circle to read to 20 or 30 seconds, extra 10.00 No. 188 Graduation of No. 138 Vertical Circle to read to 20 or 30 seconds, extra 15.00 No. 189 Graduation of No. 138 Vertical Circle to read to 10 seconds 35.00 No. 190 Burt Solar Attachment, with declination arc, hour circle, polar axis, patent latitude level, adjusting level and adjusting bar (see page 115) 96.00 No. 192 Solar Screen, to fit eyepiece of telescope (see page 106) 12.00 No. 193 Patent Latitude Level, for use with Burt Solar Transit 9.00 No. 196 Striding or Adjusting Level 8.00 No. 197 Adjusting Bar for Solar Attachment of Transit 2.25 For prices of Parts of Instruments Liable to Loss or Injury, see pages 21 to 25. SURVEYORS COMPASSES Vernier Compass Price Postage No. 226 5 in. needle, brass cover, outkeeper, mahog- any box and Jacob staff mountings (see page 150) $65.00 Attachments and Extras for No. 226 Compass No. 241 Leveling Adopter (see page 158) 10.00 .40 No. 242 Leveling Head, with four leveling screws and clamp and tangent fitted to use with Tripods Nos. 415, 420 and 425 (for Tripods see page 238) 25.00 W. & L. E. GURLEY, TROY, NEW YORK Price Postage No, 262 Achromatic Telescope, 9 in., aperture of objective 0.69 in., power about 20 diam., with platinum cross wires and stadia wires, level, clamp and tangent and 3 in. vertical circle, reading by vernier to 6 min., (see page 160) $63.00 .60 No, 268 Offset Standard with counterpoise, to bring the telescope over the line of zeros (see page 162) 10.00 Pocket Compass with Limb No. 286 6 in. limb, with one vernier reading to one minute, 3% in. needle, folding sights, two levels, mahogany box, Jacob staff mount- ings and tripod (see page 168) 76.00 Or with Extension leg tripod 80.00 Compass with Limb and Telescope No. 294 4 in. limb, with one vernier reading to one minute, 4% in. needle, 6.6 in. telescope, level on telescope, clamp and tangent to telescope axis, 4 in. vertical circle with vernier to one minute, leveling head, ma- hogany box and solid round leg tripod (see page 167) 150.00 Or with Extension leg tripod 166.00 Pocket Vernier Compass No. 300 3% in. needle, folding sights, two levels, mahogany box and Jacob staff mountings (see page 180-A) 28.00 .70 No. 305 4y a in. needle, folding sights, two levels, mahogany box and Jacob staff mountings (see page 180-A) 33.00 1.00 No. 491 Leather Pouch for No. 300 5.75 .20 No. 492 Leather Pouch for No. 305 7.00 .26 ATTACHMENTS AND EXTRAS FOR POCKET COMPASSES No. 325 Clamp and Tangent to ball spindle of Com- passes Nos. 285, 300 and 305 6.00 No. 326 Rack and Pinion to variation arc of Com- passes Nos. 300 and 305 6.00 No. 327 Leveling Adopter for Compasses Nos. 285, 300 and 305 7.50 .26 Geologists Compass (Aluminum) No. 335 United States Forest Service pattern, 2% in. needle, graduated movable sighting circle, graduated base, variation arc, fold- ing sights, two levels, clinometer, mahog- any box and Jacob staff mountings (see page 171) 36.00 .85 No. 490 Leather Pouch for No. 336 6.00 .20 6 W. & L. E. GURLEY, TROY, NEW YOEK Miners Compasses or Dip Needles For prospecting for magnetic iron ore Price Postage No, 341 3 in. needle with stop, glass on both sides and brass covers (see page 174) $20.00 .35 No. 341-A 3 in. needle with stop, glass on both sides, brass covers and attached level 23.00 .35 No. 490 Sole Leather Pouch with belt loop for Nos. 341 and 341-A 5.00 .20 Dial Compass (Aluminum) No. 350 2% in. needle with hour circle graduated for any latitude between 20 and 50 de- grees, as ordered; graduated base, grad- uated movable sighting circle, variation arc, one folding sight, one removable sight, two levels, clinometer, mahogany box and Jacob staff mountings 40.00 .45 Special Sight for latitude above 50 degrees 12.00 Extra Hour Circles graduated for any lati- tude between 20 and 50 degrees to fit Dial Compass, each 6,00 .14 No. 490 Sole Leather Pouch (see page 176) 5.00 .20 Wood Box Pocket Compasses No. 3153 Mahogany case, 3% in. square by 1% in. deep, needle circle graduated on raised ring to whole degrees, figured to 90 each way, needle 2 in. long with jeweled center and automatic stop, hinged cover with clasp, weight 4 oz 4.00 .15 No. 3154 Like No. 3153, but with needle circle figured to 360 (see page 180) 4.00 .15 No. 3155 Like No. 3153, but 3% in. square by 1% in. deep, needle 2% in. long, needle circle figured to 90 each way, weight 5 oz. 5.00 .20 Piano Hinge, full width of cover, instead of two small hinges on Nos. 3153, 3154 or 3155, extra 1.00 Township Diagram on inside of cover of Nos. 3153, 3154 or 3155, extra 1.00 LEVELING INSTRUMENTS Engineers Wye Levels No. 375 22 in. telescope, power 42 diam 225.00 No. 377 18 in. telescope, power 32 diam 215.00 No. 378 15 in. telescope, power 26 diam 205.00 All of the above Levels are equipped with mahogany box and split leg tripod. W. & L. E. GTTRLEY, TROY, NEW YORK 7 Attachments and Modifications for Engineers Wye Levels Not. 375, 377 and 378, when ordered with the instruments can be supplied as follows: Price Stadia Wires of platinum, adjustable, disappearing or fixed No extra charge Morocco Finish, on telescope and level tube No extra charge Level Vial, extra sensitive, value ten seconds to one-tenth of an inch (instead of regular vial), extra $10.00 Pinion Movement to objective slide, for Level No. 378, extra 8.00 Dust Guard to objective slide, for Level No. 378, extra... 8.00 Horizontal Limb, full circle, 3.5 in. diameter, graduated to degrees, reading by vernier to 5 minutes, as shown on page 185, extra 25.00 Compass, with needle circle graduated to degrees, needle 3 in. long, with stop. Attached on top of telescope and secured with two clamp screws, as shown on page 185, extra 25.00 Mirror, for observing level bubble from eyepiece end of instrument, as shown on page 185, extra 15.00 Reflector No. 166, for illuminating cross wires. Similar to No. 165, (see page 103) 15.00 Waterproof Hood, extra 1.25 Extension Leg Tripod No. 440, instad of split leg tripod, extra 3.00 Sole Leather Carrying Case, to enclose mahogany box, 22.00 to 26.00 Sole Leather Case, for extension tripod, extra 25.00 Canvas Case with leather mountings, for extension tripod, extra 15.00 Special Outside Packing Box with hinged cover and lock, lined inside with rubber cushions, for convenience in reshipping, extra 8.00 Architects Wye Level No. 381 12 in. telescope, mahogany box and solid round leg tripod 125.00 Attachments and Extras for No. 381 Level When Ordered with the Instrument Stadia wires of Platinum, adjustable, disappearing or fixed No extra charge Pinion Movement to eyepiece 8.00 Dust Guard to objective slide 8.00 Compass, with full needle circle graduated to whole degrees, figured to 90 each way, needle 3 in. long, with stop. Attached on top of telescope and secured with two clamp screws 25. 00 W. & L. E. CKTRLEY, TROY. Price Waterproof Hood ........................................ $1.25 Split Leg Tripod No. 436, instead of solid round leg tripod 3.00 Extension Leg Tripod No. 441, instead of solid round leg tripod ............................................... 8.00 Explorers Level No. 384 6.5 in. telescope, leather covered mahogany box and jointed extension leg tripod (see page 197) 120.00 HAND LEVELS No. 643 Locke Level, Gurley make (see page 202) ...... 9.25 Or Locke Level, Taylor make .................. 7.50 No. 646 Abney Level (see page 203) .................. 15.50 No. 640 Monocular Level (see page 204) ............... 20.00 TRIPODS Instructions for Ordering Tripods The majority of the Nos. 400 to 443 include more than one size tripod. For instance, No. 400 covers two sizes; one size for Transits Nos. 6-A to 18-A. and another size for Transits Nos. 25-A to 32-A and Nos. 25 to 30. Therefore, when ordering a separate tripod, the customer should always specify the catalogue number of the instrument for which it is intended; also give the inside diameter of the bottom plate of the leveling head. If the instrument is very old, it will be necessary to send us the bottom plate of the leveling head. Transit Tripods No. 400 Solid Round Leg Tripod, for Transits Nos. 6-A to 32-A (except Nos. 20-A to 24-A) ......... $15.00 No. 401 Solid Round Leg Tripod, for Transits Nos. 20-A to 24-A and Nos. 102 and 103.. ............. 12.00 No. 405 Split Leg Tripod, for Transits Nos. 6-A to 32-A (except Nos. 20-A to 24-A) ................. 20.00 No. 406 Split Leg Tripod, for Transits Nos. 20-A to 24-A and Nos. 102 and 103 ....................... 15.00 No. 410 Extension Leg Tripod, for Transits Nos. 6-A to 32-A (except Nos. 20-A to 24-A) ............ 23.00 No. 411 Extension Leg Tripod, for Transits Nos. 20-A to 24-A and Nos. 102 and 103 .................. 20.00 No. 412 Jointed Extension Leg Tripod, with canvas case, for Transits Nos. 20-A to 24-A ............. 25.00 Compass Tripods No. 415 Solid Round Leg Tripod, for Compass No. 226.. 10.00 No. 416 Solid Round Leg Tripod, for Compasses Nos. 285, 294. 300, 305, 335 and 350 ............ 9.00 No. 420 Split Leg Tripod, for Compass No. 226 ......... 15.00 No. 421 Split Leg Tripod, for Compasses Nos. 285, 294, 300, 305, 335 and 350 ........................ 12.00 No. 425 Extension Leg Tripod, for Compass No. 226... 20.00 No. 426 Extension Leg Tripod, for Compasses Nos. 285, 294, 300, 305, 335 and 350 .................. 15.00 W. & L. E. GURLEY, TROY, NEW YORK Level Tripods No. 430 Solid Round Leg Tripod, for Levels Nos. 375 to 378 ..................................... No. 431 Solid Round Leg Tripod, for Level No. 381... No. 435 Split Leg Tripod, for Levels Nos. 375 to 378. . No. 436 Split Leg Tripod, for Level No. 381 .......... No. 440 Extension Leg Tripod, for Levels Nos. 375 to 378 No. 441 Extension Leg Tripod, for Level No. 381 ...... No. 443 Jointed Extension Leg Tripod, with canvas case, for Level No. 384... Price $15.00 12.00 15.00 23.00 20.00 25.00 No. 494 No. 496 No. 497 Carrying Cases for Tripods To protect the tripod in transportation, a carrying case can be furnished. One style of case is substantially made of heavy canvas, with leather trimmings. Another form is made of sole leather, with cap and carrying handle. Leather Case, with cap and carrying handle, for extension tripod Canvas Case, with leather trimmings, for solid round leg, or split leg tripod Canvas Case, with leather trimmings, for ex- tension tripod 25.00 18.00 15.00 PLUMMETS Brass Plummets Plain No. 450 Plummet, screw head, steel point, 6 oz. No. 452 Plummet, screw head, steel point, 10 oz. No. 454 Plummet, screw head, steel point, 16 oz. No. 456 Plummet, screw head, steel point, 24 oz. No. 458 Plummet, screw head, steel point, 32 oz. No. 460 Plummet, screw head, steel point, long neck 12 oz Price Postage $1.50 .15 2.00 .20 3.00 .25 3.50 .35 4.00 .45 2.50 .25 Brass Plummets Adjustable This Plummet has a concealed reel, R, around which the string is wound by turning the milled head, K, on top. The friction upon the reel will hold the Plummet at any desired point of the line. No. 465 Adjustable Plummet, 10 oz 5.00 .20 Spads, Stake Tacks, Plummet Cord No. 471 Iron Spads, for suspending plummets in mines, per 100 2.00 .15 No. 472 Stake Tacks, galvanized, 2 oz, box .10 .04 No. 473 Stake Tacks, galvanized, 1 Ib. box 55 .20 No. 474 Plummet Cord, braided linen, per 25 yards .38 .04 10 W. & L. E. GTTRLEY, TROY, NEW YORK LEATHER CASES AND POUCHES Sole Leather Cases, with Shoulder Straps to fit outside the wooden box, Price Postage No. 475 Case for Precise Transits Nos. 6-A to 18-A. . $25.00 No. 476 Case for Light Mountain and Reconnoissance Transits Nos. 25-A to 30; 102 and 103.. 22.00 No. 476-A Leather covered mahogany box for Explorers Precise Transits Nos. 20-A to 24-A 20.00 No. 478 Case for Compass No. 226 17.50 No. 479 Case for Engineers Wye Levels; No. 375. No. 377. No. 378. No. 480 Case for Architects Wye Level No. 381. 26.00 24.00 14.50 No. 481 Case for Telescopic Alidades Nos. 584-B or 584-C 24.00 No. 482 Leather covered mahogany box for Explorers Telescopic Alidade No. 592-C 20.00 No. 485 Case for Compasses Nos. 335 and 850 6.00 .22 No. 486 Case for Compass No. 300 6.50 .32 No. 487 Case for Compasses Nos. 285 and 305 7.50 .50 Sole Leather Pouches, with Shoulder Straps Fitted to receive Pocket Compasses with- out wooden box. No. 490 Pouch for Compasses Nos. 335, 341, 341-A and 350 5.00 .18 No. 491 Pouch for Compass No. 300 5.75 .28 No. 492 Pouch for Compass No. 305 7.00 .38 Tripod Cases No. 494 Leather Case with cap and carrying handle for extension leg tripod 25.00 No. 496 Canvas Case with leather trimmings for solid round leg or split leg tripod 18.00 No. 497 Canvas Case with leather trimmings for extension leg tripod 15.00 Engineers Leather Field Bag No. 498 Heavy sole leather with two extra pockets, with shoulder strap, inside measure 9 in. long, 7 in. high, 2% in. wide 8.00 .35 LEVELING RODS, STADIA RODS AND SIGHT RODS No. 500 Philadelphia Rod, 2 ply, 7-3/10 ft. closed, sliding to 13 ft., graduated to feet, lOths and lOOths, with verniers reading to lOOOths, and with Micrometer target (see page 210) 22.50 No. 500- A Philadelphia Rod, 2 ply, 6-8/10 ft. closed, sliding to 12 ft., graduated to feet, lOths and lOOths, with verniers reading to lOOOths, and with Micrometer target... 22.50 Either of the above Rods with Plain target (no micrometer) 20.00 W. & L. E. GURLEY, TROY, NEW YORK 11 Price No. 500-R Service Rod, self -reading, 2 ply, 7-3/10 ft. closed, sliding to 13 ft., graduated to feet, 10th and lOOths, with verniers reading to lOOOths and with oval target (see page 211) $15.00 No. 500-B Philadelphia Rod, 2 ply, 7-3/10 ft. closed, sliding to 13 ft., graduated to feet, lOths and half lOths, with both target and rod reading to natural scales to lOOths; the lOths figures are 0.06 ft. high (see page 212) 20.00 No. 501 Philadelphia Rod, 3 ply, 5-3/10 ft., closed, sliding to 13 ft., graduated to feet, lOths and lOOths, with verniers reading to lOOOths (see page 213) 27.50 Nos. 500-B and 501 have plain targets. If with Micrometer target, add 2.50 If with Angle target, add 2.60 If with Micrometer Angle target, add 3.50 No. 501-B Special Self-reading Rod, 3 ply, 7-6/10 ft. closed, sliding to 20 ft., graduated on four faces to feet and lOths, and on back of the front section to feet, lOths and lOOths; also reading by two scales to half- hundredths. With aluminum target and canvas case (see page 214) 31.25 No. 502-A Philadelphia Mining Rod, 2 ply, 3-3/10 ft. closed, sliding to 5 ft., graduated to feet, lOthg and lOOths, with vernier reading to lOOOths 18.00 Canvas Cases for Rods Nos. 500, 500-A, 500-R, 500-B and 501 4.50 No. 505 New York Rod, 2 ply, 6-8/10 ft. closed, sliding to 12 ft., graduated to feet, lOths and lOOths, with vernier reading to lOOOths (see page 215) 20.00 No. 510 Architects Rod, 2 ply, 5% ft. closed, slid- ing to 10 ft., graduated to feet, inches and 16ths (see page 216) 10.00 No. 511 Architects Rod, 2 ply, 5% ft. closed, slid- ing to 10 ft., graduated to feet, lOths and lOOths, with verniers reading to lOOOths 10.00 No. 513 Telemeter or Stadia Rod, without target, hinge joint, 6 ft. folded, unfolding to 12 ft., graduated to feet, lOths and lOOths (see page 220) 15.00 No. 514 Telemeter or Stadia Rod, without target, hinge joint, 7 ft. folded, unfolding to 14 ft., graduated to feet, lOths and lOOths. . 16.00 No. 514-B Stadia Rod, one piece, without target, 10 ft. long, 4 in. wide, with brass ends, graduated on recessed face of 3% in. width to feet, lOths and 2/100ths (see page 218) 12.50 No. 514-C Stadia Rod, similar to No. 514-B, but 12 ft. long 15.00 12 W. & L. E. GTTRLEY, TROY, NEW YORK The graduations of Nos. 514-B and 514-C begin at the base and end at the top of the rods. The illustration on page 218 does not show completed graduations. No. 514-D Stadia Rod, one piece, without target, 10 ft. long, 3 l / s in. wide, with brass ends, graduated on flat face to feet, lOths and 2/100ths (see page 218) No. 514-E Stadia Rod, similar to No. 514-D, but 12 feet long Hinge Joint for Stadia Rods Nos, 514-B, 514-C, 514-D or 514-E, to permit folding, extra Rods Nos. 513 to 514-E can be furnished in any length up to 16 ft. Prices on appli- cation. No. 515 Telescopic Rod, 3 ply, without target, 5 ft. closed, sliding to 14 ft., graduated to feet, lOths and lOOths No. 516 Cross Section Rod, one piece, without target, 10 ft. long, with level at each end, grad- uated to feet, lOths and lOOths (see page 221) No. 517 Slip- Jointed Leveling or Stadia Rod, 12 ft. long, two inch graduated, recessed face, three sections (two slip joints), graduated in feet, lOths and lOOths. The joints are secured and released by spring catches. (See page 217). With canvas carrying case No. 518-A Plain Rod, one piece, without target, 10 ft. long, graduated to feet, lOths and lOOths (see page 221) No. 518-B Plain Rod, without target, hinge joint, 5 ft. folded, unfolding to 10 ft., graduated to feet, lOths and lOOths No. 519-A Plain Rod, one piece, without target, 12 ft. long, graduated to feet, lOths and lOOths No. 519-B Plain Rod, without target, with hinge joint, 6 ft. folded, unfolding to 12 ft., grad- uated to feet, lOths and lOOths No. 520-A Plain Rod, one piece, without target, 14 ft. long, graduated to feet, lOths and lOOths No. 520-B Plain Rod, without target, with hinge joint, 7 ft. folded, unfolding to 14 ft., grad- uated to feet, lOths and lOOths No. 521-B Plain Rod, without target, with hinge joint, 8 ft. folded, unfolding to 16 ft., grad- uated to feet, lOths and lOOths No. 522-A Plain Rod, 2 ply, without target, 5-3/10 ft. long, sliding to 10 ft., graduated to feet, lOths and lOOths No. 522-B Plain Rod, 2 ply, without target, 6-3/10 ft. long, sliding to 12 ft., graduated to feet, lOths and lOOths No. 522-C Plain Rod, 2 ply, without target, 7-3/10 ft. long, sliding to 14 ft., graduated to feet, lOths and lOOths... Price 10.50 5.00 25.00 17.50 17.00 7.50 11.25 8.75 13.75 10.00 15.00 16.25 11.25 12.50 13.75 W. & L. E. GURLEY, TROY, NEW YORK 13 Price Postage No. 524-A Plain Rod, 4 ply, without target, 3-3/10 ft. long, sliding to 11-2/10 ft., graduated to feet, lOths and lOOths (see page 223)... $17.50 Canvas Case for No. 524-A 3.00 No. 525-B Pocket Rod, 10 ft. long, graduated to feet, lOths and lOOtlis (see page 229) 4.50 .25 No. 526-A Pocket Rod, 12 ft. long, graduated to feet, lOths and lOOths 5.50 .28 No. 526-B Pocket Rod, 12 ft. long, graduated to feet, inches and 8th 5.50 .28 No. 527 Pocket Rod, 14 ft. long, graduated to feet, lOths and lOOths 7.00 .30 No. 528 Pocket Rod, 3% meters long, graduated to centimeters 5.50 .30 No. 530 Wooden Leveling Pole and Flagstaff, 7 ft. long 6.25 No. 531 Wooden Leveling Pole and Flagstaff, 9 ft. long 7.50 No. 534 Wooden Flagstaff, octagonal, 6 ft. long... 3.50 No. 535 Wooden Flagstaff, octagonal, 8 ft, long 1 . . . 4.25 No. 536 Wooden Flagstaff, octagonal, 10 ft. long... 5.25 (see page 230). No. 537-A Jointed Wooden Flagstaff, round, 6 ft. long, in 2 sections 5.50 No. 537-B Jointed Wooden Flagstaff, round, 6 ft. long, in 2 sections and with canvas case 8.75 No. 537-C Jointed Wooden Flagstaff, round, 6 ft. long, in 3 sections 8.75 No. 537-D Jointed Wooden Flagstaff, round, 6 ft. long, in 3 sections and with canvas case 12.00 No. 538-A Jointed Wooden Flagstaff, round, 9 ft. long, in 3 sections 9.50 No. 538-B Jointed Wooden Flagstaff, round, 9 ft. long, in 3 sections and with canvas case 13.00 (see page 232). No. 540-A Steel Ranging Pole, solid, hexagonal, 6 ft. long, y a in. diameter 4.00 No. 540-B Steel Ranging Pole, solid, hexagonal, 8 ft. long, % in. diameter 4.76 No. 541 Iron Tubular Ranging Pole, 6 ft. long, 13/16 in. diameter 3.75 No. 543 Iron Tubular Ranging Pole, 8 ft. long, 13/16 in. diameter 4.50 No. 544 Iron Tubular Ranging Pole, 10 ft. long, 13/16 in. diameter 5.00 (see page 231). No. 550-R Gurley Precise Leveling Rod, cross-shape section, graduated on three faces to yards, lOths and lOOths, reading to 3y a yards, with silver-faced plugs at each half yard. Fitted with wooden handle, thermometer, fixed circular rod level, canvas case, turning point and plate. Packed in a special pine box with hinged cover, han- dles and lock (see page 227) 110.00 14 W. & L. E. GTJRLEY, TEOY, NEW YOEK Price No. 551-R Molitor Precise Leveling Rod, T-shape sec- tion, 12 ft. long, graduated to feet, lOths and lOOths, or to millimeters if pre- ferred, and with circular level, two wooden handles, plumbing attachment and plum- met, enclosed thermometer, canvas case, and turning point. Packed in special pine box with hinged cover, handles and lock (see page 224) $85.00 No. 552-R Self -Reading Tape Leveling Rod; rod made of pine, 10 ft. B l / z in. long, and graduated on one edge to feet and lOths. The steel ribbon graduated to feet, lOths and half-lOths; all graduations on rod and tape are painted (see page 225) 47.50 Canvas Case for above rod 5.00 ROD LEVELS No. 545 (See page 233) 5.00 No. 546 (See page 234) 6.00 No. 547 (See* page 235) 10.00 No. 548 (See page 236) 13.00 PLANE TABLES Plane Tables, Equipment and Parts (See pages 243 to 259) No. 570 Johnson Plane Table Movement and split leg tripod , 45.00 No. 570-A Johnson Plane Table Movement and exten- sion leg tripod 57.00 No. 571 Johnson Plane Table Movement, special light weight model, with special light weight extension leg tripod 50.00 Canvas Case, leather trimmed, for No. 571 9.00 No. 573 Drawing Board, 31 x 24 in., with brass screw plate fitted, and with eight clamp screws and sockets for paper 9.00 Canvas-covered Wooden Case for No. 573.. 8.00 Flexible Canvas Case with shoulder strap, for No. 573 4.75 Eggshell Drawing paper, single mounted, 31 x 24 in., per sheet 1.25 Eggshell Drawing Paper, double mounted (muslin between), so that drawings can be made on both sides, 31 x 24 in., per sheet 2.50 No. 573-A Drawing Board, 18 x 24 in., with brass screw plate fitted, and eight clamp screws and sockets for paper 8.00 Canvas-covered Wooden Case for No. 573-A 6.25 Flexible Canvas Case with shoulder strap, for No. 573-A 3.00 Eggshell Drawing paper, single mounted, 18 x 24 in., per sheet 85 W. & L. E. GTTRLEY, TROYJEW YORK 16 Price Eggshell Drawing Paper, double mounted (muslin between), so that drawings can be made on both sides, 18 x 24 in., per sheet $1.60 Note: If desired, we can supply a Drawing Board, 20 x 20 in., together with Cases and Paper, for the same prices as listed under No. 573-A. No. 573-B Drawing Board, 15 x 15 in., with brass screw plate fitted and four clamp screws and sockets for paper 6.00 Flexible Canvas Case with shoulder strap, for No. 573-B 2.50 Eggshell Drawing paper, single mounted, 15 x 15 in., per sheet 50 Eggshell Drawing Paper, double mounted (muslin between), so that drawings can be made on both sides, 15 x 15 in., per sheet 1.10 No. 573-X Drawing Board, 31 x 24 in., with brass screw plate fitted, and with eight clamp screws and sockets for paper. Especially constructed for use in tropical climates, of heavy stock and with expansion cleats 11.00 Flexible Canvas Case with shoulder strap, for No. 573-X 8.25 No. 574 Plumbing Arm and 10 oz. plummet 6.25 No. 575 Combined Compass with levels and square base - . 25.00 For Nos. 570, 570- A or 571 Leather Hood to protect Johnson Tripod Head 3.00 Tipper or Lower Wing Nut Clamp Screw, A or B, each 1.60 Keeper Screw, C, each .20 Bolt with Wing Nut and Washer, for tripod head, each 1.10 Wing Nut for tripod bolt, each 45 Extra Board Plate, each 3.30 Clamp Screw and Socket for paper, complete, each. . . .40 Clamp Screw only, each .20 Socket only, each 20 Cap for Johnson Tripods Nos. 570, 570-A or 571 1.25 Split Tripod Legs for No. 570, each 3.30 Extension Tripod Legs for No. 570, each 7.50 Extension Tripod Legs, special light weight model, for No. 571, each... 6.25 16 W. & L. E. GITRLEY, TEOY, NEW YORK Plane Table Outfits U, S. Geological Survey Standard No. 576-C Plane Table Outfit, consisting of Johnson Movement No. 570, with split leg tripod; Drawing Board No. 573, 31 x 24 in., with brass screw plate fitted, and with eight clamp screws and sockets for paper $54.00 Flexible Canvas Case with shoulder strap, for No. 573 Drawing Board 4.75 Plumbing Arm and Plummet, No. 574 6.25 Alidade No. 584-C, with 11 in. telescope, inverting eyepiece with diagonal prism, power about 22 diameters, enlarged object- ive, 1.38 in. aperture, platinum cross wires and stadia wires; detachable striding level with revolving shield; edge graduated vertical arc reading to 1 min., combined with Beaman Stadia Arc; clamp and tangent to telescope axis; blade 18 x 3 in., with left hand edge beveled; circular level, and box compass with 4 in. needle, mounted on blade. In mahogany carrying case. See illustration on page 246 200.00 Complete, as shown on page 244 265.00 No. 576-B Plane Table 'Outfit, like Outfit No. 576-C, but with Alidade No. 584-B substituted for Alidade No. 584-C 265.00 ALIDADES, Telescopic No. 584-C Telescopic Alidade, as described above, in Outfit No. 576-C, and as shown on page 246 200.00 No. 584-B Telescopic Alidade, similar to Alidade No. 584-C, but equipped with an erecting eye- piece, power about 26 diameters, objective 1.19 inches aperture 200.00 A Gradienter can be combined with the clamp and tangent movement on Alidades Nos. 584-C or 584-B, at an extra cost of $18.00. If Alidade No. 584-C or No. 584-B is desired without the Beaman Stadia Arc attach- ment, deduct $45.00. Parts (or Alidades Nos. 584-C and 584-B No. 585 Box Compass, rectangular metal case, 4 in. needle, for Alidades Nos. 684-B or 584-C 12.50 Striding Level, complete 20. 00 Extra Glass Vial only, for Striding Level... 2.25 Circular Level, complete 6.50 Extra Glass Vial only, for Circular Level.. 4.50 Quarter interval wire, midway between upper stadia wire and horizontal cross wire. . . 2.75 W. & L. E. GTJRLEY. TROY, NEW^ YOBK 17 Explorers Alidade, Telescopic Price No. 592-C 11 in. blade, one edge beveled and grad- uated to 1/50 in., box compass with 4 in. needle, circular level, 8 in. telescope, aperture 1 in., power about 13 diameters, platinum cross wires and stadia wires, spiral movement to eyepiece, pinion move- ment to objective slide, Gradienter, com- bined with clamp and tangent to telescope axis, detachable striding level, sensitive- ness about 90 seconds, vertical arc reading by vernier to one minute, vernier movable by tangent screw, Beaman Stadia Arc, combined with the vertical arc, mahogany carrying case. Weight 3.25 Ibs., with case 5 Ibs. (see page 249) $154.00 Extras for No. 592-C Alidade Striding Level Vial, sensitiveness 60" or 40" No extra charge If the Beaman Stadia Arc is omitted, deduct 22.00 If the Gradienter is omitted, deduct 9.00 Special Graduations on Blade, extra 6.50 Striding Level, complete 16.50 Extra Glass Vial only, for Striding Level. . 1.65 Circular Level, complete 5.50 Extra Glass Vial only, for Circular Level.. 3.85 Quarter interval wire, midway between the upper stadia wire and horizontal cross wire 2.75 Leather covered mahogany box instead of plain box 10.00 Explorers Plane Table Outfits No. 592-D Explorers Plane Table Outfit, consisting of Johnson Movement No. 570, with split leg tripod; Drawing Board No. 573-A, 18 x 24 in., with brass screw plate fitted, and eight clamp screws and sockets for paper. Flexible Canvas Case with shoulder strap, for No. 573-A Drawing Board. Explorers Alidade No. 592-C, with Gradien- ter and Beaman Stadia Arc. Complete 210.00 No. 592-F Explorers Plane Table Outfit, consisting of Johnson Movement No. 571, special light weight model, with special light weight extension leg tripod; Drawing Board No. 573-A, 18 x 24 in., with brass screw plate fitted, and eight clamp screws and sockets for paper. Flexible Canvas Case with shoulder strap, for No. 573-A Drawing Board. Explorers Alidade No. 592-C, with Gradien- ter and Beaman Stadia Arc. Complete, as shown on page 249 215.00 18 W. & L. E. GITRLEY, TEOY, NEW YORK Price No. 592-H Explorers Plane Table Outfit, consisting of Johnson Movement No. 571, special light weight model, with special light weight extension leg tripod; Drawing Board No. 573 -B, 15 x 15 in., with brass screw plate fitted, and four clamp screws and sockets for paper. Flexible Canvas Case with shoulder strap, for No. 573-B Drawing Board. Explorers Alidade No. 592-C, with Gradien- ter and Seaman Stadia Arc, complete as specified on page 249 $212.50 Paper for Drawing Boards Nos. 573-A and 573-B For No. 573-A For No. 678-B 18 z 24 in. 15 z 15 in. Eggshell Drawing Paper, single mounted, per sheet $0.85 $0.50 Eggshell Drawing Paper, double mounted (muslin between), so that drawings can be made on both sides, per sheet 1.50 1.10 Traverse Plane Table Outfit No. 686 Consisting of Traverse Movement No. 587, with solid round tripod legs; No. 573-T Drawing Board, 15 x 15 in., with spring board plate, Box Compass No. 588 in- serted in one edge, and four clamp screws and sockets for paper; Ruler Sight Alidade No. 589, with graduated edge, folding sights and leather pouch; com- plete as shown on page 257 38.50 Extras for Traverse Plane Table Extension Leg Tripod, instead of Solid Round Leg Tripod, extra 6.50 Jointed Extension Leg Tripod, closing to 23 in., with canvas case, instead of Solid Round Leg Tripod, extra 16.00 Flexible Canvas Case with shoulder strap, for Drawing Board No. 573-T, extra 2.50 Eggshell Drawing Paper, single mounted, 15 x 15 in., per sheet 50 Eggshell Drawing Paper, double mounted (muslin be- tween), so that drawings can be made on both sides, 15 z 15 in., per sheet 1.10 No. 587 Traverse Plane Table Movement, with solid round leg tripod; Drawing Board, 15 x 15 inches, with spring board plate, and four clamp screws and sockets for paper. ... 16.50 No. 573-T Drawing Board, 15 x 15 in., with spring plate fitted, and with four clamp screws and sockets for paper 6.00 W. & L. E. GURLEY, TROY, NEW YORK 19 Price No. 588 Box Compass, rectangular metal case, 4 in. needle $10.00 No. 589 Ruler Sight Alidade, 10 in. long, with grad- uated edge, folding sights and leather pouch 15.00 Spring Plate for Drawing Board, each 2.50 Center Plunger Clamp Screw, complete, each 3.00 Clamp Screw and Socket for paper, complete, each... .40 Solid Round Tripod Legs, each 1.75 Extension Tripod Legs, each 4.00 Bolt, with wing nut and washer, for tripod head, each 1.00 Wing Nut for tripod bolt, each 45 Pocket Sight Alidade No. 590- A Pocket Alidade, 6 in. long, with graduated edge and folding sights, and with leather case having pencil pockets (see page 259) 9.50 No. 590-B Extra Folding Sights, for Alidade No. 590-A, per pair 4.00 SKETCHING CASES No. 594 Army Sketching Case, Glenn S. Smith Model, with one Protractor card, as selected (see page 261) 25.00 Extras for the Above Extra Protractor Cards, each 1.00 Distance between each circle Scale A, 1 inch to 1 mile 132 ft., or 1/40 mile 'Scale B, 2 inches to 1 mile 66ft., or 1/80 mile Scale C, 3 inches to 1 mile 52.8 ft., or 1/100 mile Scale D, 1 to 24,000 1/100 mile and and 1 to 48,000 1/50 mile Scale F, 1 to 100,000 Metric 100 meters (10 to 1 kilo) *Scale B is also suitable for a map scale, 1 inch to 400 feet, each circle representing 10 feet distance. Flexible Canvas Pouch, with leather shoulder strap... 2.25 Sole Leather Pouch, with shoulder strap 7.50 Tripod, with solid round legs 4.50 Staff, 2 ft. long, with metal shoe 1.25 Vellum Tracing Paper, in rolls, 8 x 36 in., per roll... ,10 Translucent Celluloid, in rolls, 8% x 50 in., per roll... .75 Celluloid is more durable than paper and not affected by moisture. No. 596 Fiala Scout Sketching Case 7.50 Architects Drawing Paper, in rolls 5% x 36 in., per roll, postpaid .05 20 W. & L. E. GTJTILEY^ TROY. NEW YORK CURRENT METERS Acoustic Current Meter No. 616 Acoustic Current Meter, indicating each 10th revolution, equipped with rubber tube, ear piece and connection; also two lengths of sleeve jointed wading rod, graduated to measure 4 ft. from plane of bucket wheel. Wooden case with lock and strap and including accessories of oil can, wrench, screw driver and pivot bearing (see page 277) $66.00 Accessories (or No. 616 Wading Rod, sleeve-jointed and graduated, per 2 ft. length 3.50 Canvas Case for two, three or four lengths of Rod 4.50 Time Recorder, or Stop Watch, No. 619, open face, nickel case, stem winder, with fly-back attachment for starting and stopping. Registering minutes, seconds and fifths of seconds 10.00 Electric Current Meters No. 623 Electric Current Meter with two inter- changeable commutator boxes, one indi- cating each revolution and the other indicating each fifth revolution of the bucket wheel, Covert Yoke, telephone sounder, dry battery, 20 ft. of cable, 10 Ib. lead weight and weight hanger. All packed in wooden box with lock, hooks and strap and including accessories of oil can, wrench, screw driver, extra pivot bearing, binding screws and nipple (see page 280) 110.00 No. 617 Electric Current Meter. This is like No. 623, except that it has only one com- mutator box indicating each revolution of the bucket wheel 93.50 No. 621 Electric Current Meter. This is like No. 623, except that it has only one com- mutator box indicating each fifth revolu- tion of the bucket wheel 93.50 Accessories for Current Meters Nos. 617, 621 and 623 Extra Cable, per foot .15 Extra Dry Cell Battery .35 Extra Lead Weight, 10 Ibs 5.00 Extra Lead Weight, 15 Ibs 6.25 Time Recorder, or Stop Watch, No. 619, as described above under Meter No. 616 10.00 W. & L. E. QURLEY. TROY, NEW YORK 81 Price Postage Wading Rods, sleeve-jointed and graduated, per 2 ft. length $3.50 Wading Rods, flush-jointed and graduated, for use with double-end Hanger, per 2 ft. length 3.50 Wading Rods, flush- jointed, 4 sections, graduated to measure 8 feet from plane of bucket wheel, at $3.25 per section 14.00 Double-end Hanger, for use with flush-jointed Rods.. 4.00 Base, for use with Rod 2.75 Leather Case for rods, base and hanger 13.00 Canvas Case for rods, base and hanger 4.50 Electric Register, No, 609, as described on page 281... 30.00 ELECTRIC REGISTER No. 609 (See page 281) 30.00 HOOK GAGE No. 628 (See page 283) 25.00 WATER STAGE REGISTERS No. 630 Printing Register (see page 290) 385.00 No. 632 Tape Reel for use with No. 630 Register. . 27.50 No. 633 Graphic Register with spring driven clock (see page 293) 145.00 No. 636 Graphic Register, with weight driven clock 145.00 No. 634 Graphic Register, with spring driven clock, range to 1 ft., time scale 7 days 95.00 No. 634-A Graphic Register, range to 2 ft., time scale 7 days 110.00 LONG DISTANCE WATER STAGE REGISTER No. 637 Long Distance Register (see page 296) 275.00 No. 638 Long Distance Sender (see page 299) 110.00 No. 639 Long Distance Indicator (see page 300) .... 155.00 No. 639-A Indicating Gage (see page 301) 55.00 PRECISION BALANCE No. 9570 (See page 303) 450.00 Miscellaneous Instrument Parts and Supplies Prices of Parts for Gurley Instruments, Liable to Loss or Injury Solid Round Tripod Legs only, for Engineers Transit or Level, per set 7.50 Split Tripod Legs only, for Engineers Transit or Level, per set 12.50 Extension Tripod Legs only, for Engineers Transit or Level, per set 16.00 Clamp Screw and Band for extension tripod leg, each 1.25 .05 Tripod Head only, with bolts and nuts, for Engineers Transit or Level 7.50 .50 Cap for tripod head, each 1.25 .12 22 W. & L. E. GURLEY, TROY, NEW YORK Price Postage Brass Bolt and Nut to fit tripod head, each $1.00 .05 Metal Point or Shoe for tripod leg, each 65 .05 Shawl Strap (superior), for extension tripod 1.25 .10 Steel Screw Driver with wooden handle, each .35 .05 Steel Adjusting Pins, each 08 .01 Steel Adjusting Pins, with eye, for attaching to key ring, each .20 .02 Rubber Tips, for bottom of instrument box, per set... .80 .08 Leather Strap and Buckle for transit box 1.00 .10 Leather Strap and Buckle for level box 1.25 .10 Lock and Key for instrument box 1.00 .03 Reading Glass for transit, each 1.25 .02 Brass Plummet with screw cap, for transit or level, each 2.00 .20 Waterproof Hood, for transit or level, each 1.25 .06 Clamp with Clamp Screw, for New York Rod 3.25 .15 Clamp with Scale and Clamp Screw, for Philadelphia Rod 4.00 .15 Target with Clamp Screw and Spring, for New York or Philadelphia Rod 4.00 to 8.50 .35 Chain Handle, with staple and nuts, each 1.00 .08 Chain Tallies, per set of 9 .65 .06 Instrument Oil, finest grade, small bottle 45 .05 Camel Hair Brush 1.25 .02 Parts for Gurley Transits Needle with jeweled center and center pin 5.00 .12 Center Pin only .75 .01 Ground Glass Level Vials, for plate t each 1.25 .02 Ground Glass Level Vials, brass mounted complete, for plate, each 3.00 .14 Ground Glass Level Vial, for telescope, unmounted, 2.75 to 3.50 .14 Cap for eyepiece or object glass, each 1.00 .03 Shade for object glass 1.00 .03 Clamp Screws for horizontal limb, each 1.00 .02 Tangent Screw for leveling head 1.00 to 2.00 .13 Claim* Screw for leveling head 1.00 .03 Leveling Screw for leveling head, each 1.25 to 2.00 .14 Eyepiece complete, including lenses and settings, and omitting cap 8.00 .14 Object Glass complete 8.00 .14 Platinum Cross Wires and Diaphragm 4.50 .15 Platinum Stadia Wires, adjustable, and diaphragm... 8.00 .15 Platinum Stadia Wires, fixed, and diaphragm 10.00 .15 Platinum Cross Wires only fitted to old diaphragm... 3.50 Platinum Cross Wires and adjustable Stadia Wires fitted to old diaphragm 6.00 Platinum Cross Wires and fixed Stadia Wires fitted to old diaphragm 8.00 Brass packing box for mailing any of the above diaphragms .50 *Mahogany Box with lock and strap, and fitted inside, according to size $12.00 to 15.00 *When ordering, specify length of telescope, length of compass needle, height of the instru- ment from bottom plate of the leveling head to the tops of the standards, and also state whether W. & L. E. GTTRLEY. TEOY, NEW YORK 88 Price Postage it has a vertical arc or a full vertical circle. Unless the Transit is sent to us, the new box will be furnished with the packing pieces or blocks not fitted in position. Plummet Screw and Chain for bottom of leveling head. $0.45 .04 Adjusting Pins, each 08 .01 Adjusting Pins, with eye for attaching to key ring, each 20 .02 Screw driver, small size .35 .04 Screw driver, large size 65 .08 Waterproof Hood 1.25 .10 Instrument Oil, finest grade, small bottle 45 .05 Parts for Gurley Wye Levels Ground Glass Level Vial, unmounted, graduated and figured, for 22-inch Wye Level 5.00 .25 Ground Glass Level Vial, unmounted, not graduated or figured, for 22-inch Wye Level 4.50 .25 Ground Glass Level Vial, unmounted, graduated and figured, for 15-inch, 18-inch or 20-inch Wye Level 4.50 .20 Ground Glass Level Vial, unmounted, not graduated or figured, for 15-inch, 18-inch or 20-inch Wye Level 4.00 .20 Ground Glass Level Vial, unmounted, extra sensitive (value of each graduation 10 seconds), graduated and figured, for 18-inch, 20-inch or 22-inch Wye Level 10.00 .25 Ground Glass Level Vial, unmounted, extra sensitive (value of each graduation 10 seconds), not grad- uated or figured, for 18-inch, 20-inch or 22-inch Wye Level 9.50 .25 Ground Glass Level Vial, unmounted, for Architects Level 2.25 .05 Note: Whenever possible the metal case or tube should be sent us so that the vial can be properly set. The extra cost is 75 cents. Cap for eyepiece or object glass, each 1.00 .03 Clamp Screw for leveling head 1.00 .03 Tangent Screw for leveling head 1.50 to 2.00 .13 Leveling Screw for leveling head, each 1.50 to 2.75 .14 Eyepiece complete, including lenses and settings, and omitting cap 8.00 .14 Object Glass, complete 10.00 .14 Platinum Cross Wires and Diaphragm 4.50 .15 Platinum Adjustable Stadia Wires, Cross Wires, and Diaphragm 8.00 .15 Platinum Fixed Stadia Wires, Cross Wires, and Dia- phragm 10.00 .15 "Mahogany Box with lock and strap, and fitted inside, according to size $7.50 to 15.00 *Note: When ordering, specify the exact length of the telescope when both the eyepiece and the objective slides are not extended; also state the height of the instrument from the bottom plate of the leveling head to the top of the wyes and mention the diameter of the bottom plate of the leveling head. Unless the Level is sent 24 W. & L. E. GTTRLEY, TROY. NEW YORK Price Postage to us, the new box will be furnished with the packing pieces or blocks not fitted in position. Adjusting Pins, each $0.08 .01 Adjusting Fins, with eye for attaching to key ring, each 20 .02 Parts for Surveyors Compasses with 4 in., 5 in. or 6 in. needle, like model No. 226 Needle with jeweled center and center pin 5,00 .12 Center pin only 75 .01 Ground glass level vials, each 60 .02 Ground glass level vials, brass, mounted, complete, each 2.50 .14 Brass cover for compass of our make 1.25 .25 Outkeeper 1.25 .13 Glass circle, unmounted, old style flat glass, for com- pass face 35 .15 Glass circle, unmounted, new style, beveled edge plate glass, for compass face 2.00 .15 Wrench for center pin .15 .01 Staff mountings, brass head and clamp, without spindle 2.50 .25 Staff mountings, steel point 65 .18 Cap only for staff socket or tripod head 1.00 .12 Ball spindle fitted to new or old socket 4.00 .30 Sight vanes only, each 3.00 .20 Clamp screw for spindle or sight vane .65 .03 Socket complete, including clamp screw, spring catch, needle lifting screw and lifter 10.00 .50 Needle lifter 50 .05 Needle lifting screw 65 .05 Spring catch 65 .05 Bolt with nut and washer for tripod head .85 .05 Nut and washer for tripod bolt 40 .04 Mahogany box with lock and strap 7.50 Parts for Compasses Nos. 285 and 294 Needle with jeweled center and center pin 5.00 .12 Center pin only .75 .02 Glass Circle, unmounted, beveled edge plate glass for No. 285 2.00 .15 Glass circle, unmounted, for No. 294 ,35 .15 Plate level vials only for No. 285, each 1.25 .05 Plate level vials with case and adjusting screws for No. 285, each 3.00 .14 Plate level vials only for No. 294, each 50 .04 Plate level vials with case and adjusting screws for No. 294, each 1.50 .10 Telescope level vial only for No. 294 3.00 .14 Telescope level complete for No. 294 7.50 .25 Folding sights for No. 285, each 6.00 .15 Tangent screw and nut for any movement 1.50 .12 Opposing spring plunger and case for tangent screw. . 1.25 .05 Clamp screw for telescope axis .65 .05 Clamp screw for limb or leveling head 1.00 .05 Leveling screw for No. 294 1.25 .05 Dust cap for leveling screw 50 .03 W. & L. E, GITRLEY, TROY, NEW YORK 26 Price Postage Dust cap or sunshade for objective, each $1.00 .05 Eyepiece cap 1.00 .05 Spindle and socket, clamp screw and cap for Jacob staff socket or tripod for No. 285 4.00 .20 Spindle and socket and clamp screw, without cap for No. 285 3.25 .17 Jacob staff socket and cap for No. 285 1.50 .15 Cap only for Jacob staff socket or tripod for No. 285 .75 .08 Shoe for Jacob staff or tripod leg .65 .05 Bolt with nut and washer for tripod head 85 .05 Nut and washer for tripod bolt .40 .04 Mahogany box for No. 285 5.00 .30 Mahogany box for No. 294 , 12.00 .60 Parts for Pocket Compasses Nos. 300, 305, 335 and 350 Needle with jeweled center and center pin 5.00 .12 Center pin only 75 .02 Level vials only, each .50 .04 Level vials with case and adjusting screws, each 1.50 .10 Glass circle 35 .15 Folding sights for No. 305, each 4.00 .17 Folding sights for Nos. 300, 335, and 350, each 3.50 .17 Removable sight for No. 350 2.00 .12 Needle lifting screw 35 .02 Clamp nut for variation arc 25 .02 Clamp nut for spindle .35 .02 Spindle and socket, clamp screw and Jacob staff socket with cap, for Nos. 300, 335 and 350 3.00 .15 Spindle and socket, clamp screw and Jacob staff socket with cap for No. 305 4.50 .20 Jacob staff socket and cap for Nos. 300, 335 and 350.. 1.00 .15 Jacob staff socket and cap for No. 305 1.50 .15 Cap only for staff socket or tripod for Nos. 300, 335 and 350 50 .06 Cap only for staff socket or tripod for No. 305 .75 .08 Shoe for Jacob staff or tripod leg 65 .05 Bolt with nut and washer for tripod head ,85 .05 Nut and washer for tripod bolt 40 .04 Mahogany box for No. 300, 335 and 350 3.00 .20 Mahogany box for No. 305 3.50 .25 CHAINS Made by W. & L. E. Gurley Brazed Steel Chains No. 670 33 ft., 50 links, No. 12 tempered steel wire, brazed links and rings 5.75 .45 No. 671 50 ft., 50 links, No. 12 tempered steel wire, brazed links and rings 7.00 .55 No. 672 66 ft., 100 links, No. 12 tempered steel wire, brazed links and rings 10.50 .70 No. 673 100 ft., 100 links, No. 12 tempered steel wire, brazed links and rings 11.501.00 Steel Snaps to make full chains into half chains, without extra charge, if ordered with the chain. W. & L. E. GURLEY, TROY, NEW YORK No. 708 No. 710 No. 730 No. 732 No. 740 No. 743 No. 749 No. 774 No. 776 V - 20 V - 30 No. 782 No. 786 Vara Chains (1 vara 33.333 inches) Price Postage 10 varas, 50 links, oval rings, No. 12 tem- pered steel wire, brazed links and rings $5.75 .35 20 varas, 100 links, oval rings, No. 12 tem- pered steel wire, brazed links and rings 10.50 .65 Meter Chains (1 meter 39.371 inches) 10 meters, 50 links, oval rings, No. 12 tem- pered steel wire, brazed links and rings 5.75 .45 20 meters, 100 links, oval rings, No. 12 tem- pered steel wire, brazed links and rings 10.50 .70 Marking Pins Set of 11 Pins, No. 4 iron wire, nickel- plated, 14 in. long 1.45 .50 Set of 11 Pins, 3/16 steel wire, 14 in. long, japanned red and white, alternating each inch. Quickly located in brush or grass 2.00 .40 Spring Steel Carrying Ring for marking pins .30 TAPES Steel Ribbon Chain Tapes One-quarter inch wide, heavy steel ribbon, deeply etched graduations, large detach- able handles and wooden reel with nickel- ed trimmings. Steel Ribbon, 66 ft., graduated to 100 links 7.00 .40 Steel Ribbon, 100 ft., graduated each foot 8.50 .50 The 66 foot tape has the first and last links in lOths. The 100 foot tape has the first and last feet in lOths. Metric Measure Only Steel Ribbon, 20 meters, graduated to deci- meters 6.00 Steel Ribbon, 30 meters, graduated to deci- meters 9.25 These tapes have the first meter in centi- meters with the first decimeter in milli- meters. Vara Measure Only Steel Ribbon, 20 varas, graduated to tenths of a vara 8.50 Steel Ribbon, 30 varas, graduated to tenths of a vara 10.50 .40 .50 .40 .45 Metallic Tapes Metallic Tape, 50 ft., in lOths or 12ths, and links 4.25 Metallic Tape, 100 ft., in lOths or 12ths, and links . 7.00 .30 W. & L. E. GURLEY, TROY, NEW YORK Metallic Tapes without Cases Price Postage These tapes can be put into the leather cases when the original tape line is worn out. No. 791 Metallic Tape, 50 ft., in lOths or IZths, and links $2.50 .16 No. 794 Metallic Tape, 100 ft., in lOths or 12ths, and links 5.00 .20 We can furnish Metallic Tapes Nos. 791 and 794, with metric or vara measure on reverse side, instead of links at an extra cost of two cents per foot. Reliable Steel Tapes (Best Quality) Instantaneous Readings Three-eighths inch wide, in leather case with nickeled trimmings and double folding flush handle opened by pressing on op- posite side. No. 798 Steel Tape, 100 ft., in lOths or 12ths, and links 14.75 .30 Tape No. 798 can be furnished with metric or vara measure on reverse side, instead of links, at an extra cost of two cents per foot. Reliable Junior Steel Tapes, Instantaneous Readings One-quarter inch wide, in leather case with nickeled trimmings and double folding flush handle opened by pressing on op- posite side. A convenient vest pocket tape, being an exact counterpart of the "Reliable," and not much over one-half its size and weight. No. 800 Steel Tape, 25 ft., in lOths or 12ths 4.75 .15 No. 801 Steel Tape, 50 ft., in lOths or 12ths 7.25 .20 Tapes Nos. 800 and 801 supplied with vara, metric measure, or links on reverse side, at an extra cost of two cents per foot. Wolverine Steel Tapes, Instantaneous Readings One-quarter inch wide, with open metal reel having folding handle and leather strap on reverse side, by which the tape can be firmly held when winding. No. 817 Steel Tape, 100 ft., in lOths or 12ths, and links 18.00 .35 Tape No. 817 supplied with vara or metric measure on reverse side, instead of links, without extra charge. 28 W. & L. E. GITRLEY, TROY, NEW YORK Engineers Pattern Steel Tapes (Best Quality) Instantaneous Readings Price Postage One-quarter inch wide, in cases with fold- ing flush handles, opened by pressing pin on opposite side. Nickel-plated trimmings. No. 824 Steel Tape, 100 ft., in lOths or 12th s, and links $14.50 .85 In metal lined hard leather case. No. 835 Steel Tape, 100 ft., in lOths or 12ths, and links 13.50 .35 In black enameled steel case. Tapes Nos. 824 and 835 are detachable from their cases and are furnished with an extra handle, No. 841, and can be used as a chain tape. They are graduated to feet, tenths and hundredths of feet, or to feet, inches and eighths of inches, as desired, on one side, and to links and poles, vara or metric, as desired, on the reverse side. Tape Repair Outfits No. 885 Punch and Eiveter, with two packages of eyelets 4.50 .30 This Punch cuts a clean hole in steel tapes of the usual thickness, and the eyelet is then inserted and quickly 'and neatly riveted. The punch is 7% inches long. For the repair of all tapes except heavy ribbon chain tapes. No. 887 Eureka Tape Repair Sleeves. One dozen sleeves 60 .05 Half -Dozen sleeves 40 .05 These sleeves of thin sheet metal are coated with a combination of solder and flux so sensitive that they make a per- fect adhesion with the tape by the heat of a lighted match. The repair can be made in the field in one minute. Com- plete directions accompany each set. When ordering, be sure to specify width of tape and if heavy or light ribbon. YB 24058 W. &L 800336 UNIVERSITY OF CALIFORNIA LIBRARY