UC-NRLF DEPARTMENT OF COMMERCE U. S. COAST AND GEODETIC SURVEY O. H. SUPERINTENDENT SURVEYING A PLANE TABLE MANUAL BY D. B. Assistant APPENDIX No. 7-REPORT FOR 1905 ( Reprint with corrections, January, 1915 ) WASHINGTON GOVERNMENT PRINTING OFFICE 1915 GIFT Of DEPARTMENT OF COMMERCE U. S. COAST AND GEODETIC SURVEY O. H. SUPERINTENDENT SURVEYING A PLANE TABLE MANUAL BY D. IB. Assistant APPENDIX NO. 7 REPORT FOR 1905 (Reprint with corrections, January, 1915) WASHINGTON GOVERNMENT PRINTING OFFICE 1915 1 /\ o ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 50 CENTS PER COPY CONTENTS. PRELIMINARY STATEMENT. Definitions: Page. Topographic map 295 Projection. , 295 Scale 295 Datum plane 295 Relief 295 Control 295 INSTRUMENTS. Plane table 296 Description 296 The board 296 Movements 296 Tripod 297 Mountain plane table 297 The alidade 297 Description " 297 Declinatoire 298 Metal clamps 298 Adjustments 298 Fiducial edge of rule 298 Levels attached to rule 298 Parallax 299 Axis of revolution 299 Vertical line of diaphragm 299 Middle horizontal line of diaphragm 299 Stadia rod 300 Description 300 Graduation 300 Inclined sights 301 Micrometer eyepiece .' 301 Plane-table sheet 302 Scale 302 Projections 303 Selecting limits 303 Polyconic projection 304 Method of constructing 304 Rectangular 305 Accessories 305 Weights 306 291 392 CONTENTS. FIELD WORK. Page. Organization of party 306 Preliminary reconnaissance 307 Signal poles 307 Graphic triangulation 307 Amount of control 309 Three-point problem 310 Lehman's method 311 Rule i 311 Rules 2 and 3 311 Procedure 311 Examples 312 Repetition 312 Orienting by estimation 313 Bessel's method by inscribed quadrilateral 313 Tracing cloth protractor 314 Two-point problem 314 Deflection of long lines 315 Distortion errors 316 Position by compromise 317 Application 317 Height of instrument 318 Relief 318 Hill shading 318 Contours 318 Profile 319 Advantages and disadvantages of contours and hill shading 319 Contour interval 319 Datum plane 320 Reference signal 320 Station routine 321 Number of elevations to be determined 321 Contour sketching 321 Typical contour groups , 321 Order of development of contours 322 Filling in 322 Traverse lines 322 Determinations for hydrography 323 High- water and storm-water line 324 Determination of inaccessible points 324 Large scale surveys 324 Rapid surveys 325 Military reconnaissance with plane table 325 With compass and notebook 326 Photogrammetry 326 Survey in advance of triangulation 327 Office work 328 Tables and formulae 330 ILLUSTRATIONS. Page. 1. Plane table and alidade 296 2. Plane table movement 296 3. Alidade 297 4. Stadia rods 300 5. Diagram, Construction of projection 30^ 6. Graphic triangulation 307 7. Three-point problem 3 10 8. Three-point and two-point problems 312 9. Bessels's solution of three-point problem 313 10. Diagram illustrating effect of distortion of plane table sheets 316 11. Hypsograph 318 12. Hypsograph, section and views 318 13. Diagram, Construction of profile from plan 319 14. Crest, face, and talus of a granite cliff 319 15. Elevation of a granite cliff 319 16. Typical contour groups 321 17. Conventional signs 342 18. Conventional signs 342 19. Conventional signs 342 20. Conventional signs 34 2 21. Conventional signs ' 342 22. Conventional signs 342 23. Conventional signs 34 2 24. Conventional signs 34 2 25. Conventional signs 34 2 26. Conventional signs 34 2 27. Conventional signs , 34 2 28. Conventional signs 34 2 29. Specimens of lettering 34 2 30. Sparsely settled town, salt marsh, pine woods, etc 342 31. Railroads, canals, iron bridges, etc 34 2 32. Eroded drift banks, with bowlders set free 342 33 . Blocking of cities, etc 34 2 34. Erosion of soft stratified rock 342 35. Scale of hill curves 34 2 36. Scale of shade 34 2 37. Diagram for reading elevations 34 2 2 93 APPENDIX 7. A PLANK TABLE MANUAL. By D. B. WAINWRIGHT, Assistant. PRELIMINARY STATEMENT.* A topographic map is the delineation upon a plane surface, by means of conven- tional signs, of the natural and artificial features of a locality. Every point of the drawing corresponds to some geographic position, according to some method adopted for representing the surface of the spheroid on a plane, which is called the projection. Since it is a representation in miniature, the distance between any two points on the map is a certain definite fraction of the distance between the same points in nature. This ratio is called the scale. Each point, besides being projected on a horizontal plane, has its elevation rela- tive to a level surface, in some way indicated. The level surface adopted for the map is called the datum plane, and the representation of the variations in the vertical ele- ment, the modeling of the country, is called the relief. CONTROL. All topographic surveys of importance are based upon a system of triangulation. A sufficient number of points, whose geographical positions have been determined by triangulation, properly distributed over the area to be surveyed, forms the frame- work for controlling the accurate location of the various details. * Advantage has been taken of the opportunity afforded by the preparation of a new edition of the Plane Table Manual to make a new arrangement of the "Three-point problem," with the intention of simplifying the description of the conditions found in practice and the several steps required for the graphic solution of the problem with the plane table according to Lehman's method. This method is the most rapid one, in the hands of an experienced topographer, but for those who may have only occasional use for a graphic solution Bessels's method or the tracing paper protractor method is recommended. 295 296 COAST AND GEODETIC SURVEY REPORT, 1905. INSTRUMENTS AND ADJUSTMENTS. THE PLANE TABLE. The principal instrument in use by the Coast and Geodetic Survey for mapping details is the plane table. For this purpose it is a universal instrument. All the neces- sary operations for producing a map are executed with it in the field directly from the country as a model. Other instruments are employed as auxiliaries to it under certain conditions, as will be seen later on under the head of " Field practice," but in general it fulfills all require- ments alone. Description (Illustration i). The plane table is composed of a well-seasoned draw- ing board* about 30 inches in length, 24 inches in width, and three-quarters of an inch thick, with beveled or rounded edges. It is commonly made of several pieces of white pine, tongued and grooved together, with the grain running in different directions to pre- vent warping. It is supported upon three strong brass arms, to which it is attached by screws passing through them and entering the underside of the board, the three holes for the reception of the screws being guarded by brass bushings and situated equidistant from each other and from the center of the table. By means of these screws the board can be removed at will. The movements (Illustrations i and 2) of the tables in use by the Coast and Geodetic Survey are made from several different models, but as the principal features are the same in all designs the description of one type will suffice for all. The arms to which the board is fastened rest upon the sloping upper face of a rather flat hollow cone of brass, to which they are permanently fixed. Upon its lower edge or periphery this cone is fashioned into a horizontally projecting rim, the inferior face of which is as nearly as possible a perfect plane, and this in its turn rests upon a corresponding rim of somewhat greater diameter projecting slightly beyond it. This second rim forms the upper and outer flange of a circular metal disk in the form of a very shallow cylinder. The inferior face or plane of the upper flange or rim has, at its contact with the superior face of the lower, a horizontal rotary movement about a common center which is also the center of the instrument, and the two are held together by means of a solid conical axis of brass extending upward from the center of the inner face of the lower disk. A socket of similar shape fits exactly over this axis, projecting downward from the inner side of the apex of the conical or upper disk. The two plates are held together by means of a screw with a milled head, capping the cone from the outside, and which can be loosened or removed at pleasure. A tangent screw and clamp fastened to the edge of the upper rim permit, when loose, the revolution of the table about its center, and, when clamped to the lower limb, hold the table firm while the tangent screw gives a more delicate movement. Three equidistant vertical projections of brass, grooved on the underside, and cast in one piece with the under face of the lower disk, extending from the periphery toward the center, rest upon the points of three large screws which come through a heavy wooden block below. This block, which is the top of the stand and is approximate in form to an equilateral triangle, is 2% inches thick when made- of wood. * It is contemplated having the board made of a special aluminum alloy. NO. 2. PLANE TABLE MOVEMENT. APPENDIX 7. A PLANE TABLE MANUAL. 297 The three screws last mentioned have large milled heads, are quite stout, and play through the block below by means of brass female screws let into it. They are the leveling screws of the instrument and are equidistant from its center. Upon the underside and center of the metal lower disk is a socket containing a ball with a brass arm, which projects through the center of the block from beneath. The lower end of the arm is threaded, and upon it plays a female screw with a large milled head, which can be relaxed or tightened at pleasure. The screw clamps the whole upper part of the instrument to the stand; it is loosened only before leveling and kept securely clamped at all other times. The block, made either of wood or brass,* is supported upon three legs, and with them forms the tripod or stand of the instrument, the legs being of such a length as to bring the table to a convenient height for working, and so arranged as to be taken off at will, or closed so that their brass-shod and pointed ends can be brought together or moved outward, as may be required. They are made on the open or skeleton pattern, and each is securely attached to a segment of the tripod head by a long brass bolt. MOUNTAIN PLANE TABLE. A small plane table, with a board measuring only 14 by 17 inches, is employed in reconnaissance, mountain work, or as an auxiliary to one of the standard size. All the various parts are reduced in size to correspond with the board, and the construction of the movement simplified. THE ALIDADE. The type of alidade in general use (Illustration 3) consists of a skeleton rule (12 inches long by 2^ inches wide) nickel-plated underneath, from and perpendicular to which rises a metal column (3 inches high), surmounted by Y's, receiving the trans- verse axis of the telescope, to one end of which axis is firmly attached a graduated arc of 30, each side of a central o, an accompanying vernier being attached to the Y support. The arc moves with the telescope as it is raised or depressed, and it is used in the measurement of vertical angles to determine heights. A clamp and a tangent screw placed on the other side of the telescope, opposite the arc, controls its vertical movement. The telescope is fitted accurately near its center of gravity within a closely fitting cylinder, to which is solidly attached the transverse axis. The telescope revolves within the cylinder 180, stops being fitted for that range. This affords an easy mode of adjusting the cross lines to the axis of revolution, and for correcting with a striding level the errors of level and collimation and revolution of the telescope. Upon the tube of the telescope are turned two shoulders, on which rest a striding spirit level, which can be readily reversed or removed at pleasure. The eyepiece carries the usual reticule with screws for the collimation adjustment, and to this is attached a glass diaphragm, having one vertical and three horizontal lines engraved upon it. One of the horizontal lines crosses the middle of the diaphragm, the other two are placed equidistant from it, one above and one below. The interval between them remains a constant chord for the measurement of distance upon a graduated staff or rod. * Now made of a special aluminum alloy. 298 COAST AND GEODETIC SURVEY REPORT, 1905. In some cases short auxiliary lines have been added dividing the interval into still smaller chords. Several of the alidades are furnished with a micrometer eyepiece so attached that the thread is horizontal, and has a vertical movement for measuring the angular distance of a fixed length on a rod which remains a constant chord. To the rule of the alidade are attached two spirit levels, one in the longitudinal direction of the rule and the other at right angles to it. A dedinatoire (shown in Illustration i ) accompanies the alidade and is carried in the same packing box. It consists of a rectangular brass box 7 inches long by 2 wide, with an arc at each end graduated to 15 on each side of the o. It contains a needle long enough to extend from arc to arc, and resting on a pivot midway the box. The sides running lengthwise the box are parallel to a line connecting the zero marks of the two arcs. The metal clamps, for holding the projection on the board, are of two kinds: U-shaped for the ends, and the side clamps, the latter being made of thin metal strips about 12 inches in length, with two or more springs attached to grip the underside of the board. Adjustments. From the nature of the service in some sections of the country the plane table is often necessarily subjected to rough usage, and there is a constant liability to a disturbance of the adjustments; still, in careful hands, a well-made instrument may be used under very unfavorable conditions for a long time without being perceptibly affected. One should not fail, however, to make occasional examinations, and while at work, if any difficulty be encountered which can not otherwise be accounted for, it should lead directly to an examination of the adjustments. 1. The fiducial edge of the rule. This should be a true straight edge. Place the rule upon a smooth surface and draw a line along the edge, marking also the lines at the ends of the rule. Reverse the rule and place the opposite ends upon the marked points and again draw the line. If the two lines coincide no adjustment is necessary; if not, the edge must be made true. There is one deviation from a straight line, which, by a very rare possibility, the edge of the ruler might assume, and yet not be shown by the above test; it is when a part is convex and a part similarly situated at the other end concave, in exactly the same degree and proportion. In this case, on reversal, a line drawn along the edge of the rule would be coincident with the other, though not a true right line; this can be tested by a true straight edge. 2. The levels attached to the rule. Place the instrument in the middle of the table and bring the bubble of either level to the center by means of the leveling screws of the table; draw lines along the edge and ends of the rule upon the board to show its exact position, then reverse 180. If the bubble remains central it is in adjustment; if not, correct it one-half by means of the leveling screws of the table, and the other half by the adjusting screws attached to the level. This should be repeated until the bubble keeps its central position whichever way the rule may be placed upon the table. This presupposes the plane of the board to be true. The other level should now be examined and adjusted in a like manner. APPENDIX 7. A PLANE TABLE MANUAL. Great care should be exercised in manipulation lest the table be disturbed. 3. Parallax. Move the eyeglass until the cross hairs are perfectly distinct, and then direct the telescope to some distant well-defined object. If the contact remains perfect when the position of the eye is changed in any way, there is no parallax; but if it does not, then the focus of the object glass must be changed until there is no dis- placement of the contact. When this is the case the cross hairs are in the common focus of the object and eyeglasses. It may occur that the true focus of the cross hairs is not obtained at first, in which case a readjustment is necessary, in order to see both them and the object with equal distinctness and without parallax. 4. Axis of revolution. Since the bearings of the pivots are fixed, the axis of revolution is assumed to remain parallel to the plane of the rule. 5. Vertical line of diaphragm. Point the intersection of the vertical and the middle horizontal lines of the diaphragm on some well-defined distant object; revolve the telescope in its collar 180 and again observe the object. If the intersection covers it, the adjustment is perfect; if not, one-half the error must be corrected by moving the diaphragm, by means of the adjusting screws, and the other half with the tangent screw of the table. This operation should be repeated until the adjustment is perfect. 6. Middle horizontal line of diaphragm. (i) Adjust the striding level by reversing it end for end and correcting its error half the difference by its own adjustment, half by the tangent screw of the telescope. (2) Point the telescope to a target, and note the reading, or make a mark where the wire points, when the bubble is in the middle. (3) Revolve the telescope in its collar 180, and note the reading or mark the place where the wire points, when the bubble is in the middle. (4) The mean of the two pointings is the true level line, upon which the wire is to be adjusted, which may be done in this way: Keep the bubble in the middle and by means of the adjusting screws bring the middle wire to bisect a point half way between the two readings or marks. The adjustment may be verified by revolving the telescope as in (2) and if the middle wire again bisects the point the adjustment is perfect. (5) If it is now desired to make the vernier read zero on the vertical arc, the table must be carefully leveled; and in order to do this more perfectly than can be done with the levels on the ruler, it may be done by observing the striding level; the telescope remaining clamped, the striding level should read the same in every position of the alidate when the table is perfectly level. (In general, this will be found too delicate a test, as the table is not sufficiently even for so sensitive a level to be employed. ) The table being leveled, move the telescope with the tangent screw until the bubble is in the middle, and then set the vernier to read zero; the screw holes in it are oblong, so that it admits of being pushed either way. (6) It is easy to have the adjustments near enough to serve for running curves of equal elevation, but in determining the heights of stations it is best to make the obser- vations complete, with reversals, both of level and of telescope, taking the mean of the observations, by which the errors of adjustment are eliminated. This, in fact, is always done with the theodolite, and should be done with the alidade when precision is required. ^00 COAST AND GEODETIC SURVEY REPORT, 1905. The following may serve as an example: TELESCOPE DIRECT. Reading of vernier, level direct with bubble in center 4- o ' i' Reading of vernier, level reversed with bubble in center o' Mean + o o'.$ Station, reading -f- 2 17' Angle of elevation (difference) 2 i6 / .5 TELESCOPE INVERTED. Reading of vernier, level direct with bubble in center o 2' Reading of vernier, level reversed with bubble in center - V Mean o i'.s Station . . + 2 12' Angle of elevation (difference) 2 13'. 5 Mean 2 15' It will be seen, from analyzing these observations, that the level was one-half minute out of adjustment, the horizontal wire one and one-half minutes, and that revolving the telescope in its collar 180 changed its relation to the index on the vernier by i'. The mean is free from all errors of adjustment. The stadia rod* (Illustration 3), used in the Coast and Geodetic Survey, is simply a scale of equal parts painted upon a wooden rod about 10 feet long, 4 inches wide, and i^ inches thick, so graduated that the number of divisions upon it, as seen between the upper and lower horizontal wires of the telescope when the rod is held at right angles to the line of sight, is equal to the number of units in the distance between the instrument and the rod. Graduation. In all cases the rod should be graduated for the particular instru- ment, and, if the best results are to be obtained, to suit the convenience of the observer. In practice the alidade is mounted on a stand, and its center is plumbed over one end of a hundred-meter base, measured on level ground. A line, representing the zero of the graduation, having been drawn about 5 inches from one end of the rod, the latter is held vertical at the other end of the base, zero mark upward. The observer at the alidade then makes the upper horizontal line of the diaphragm coincide with the zero and directs the rodsman by signals where to draw a line which coincides with the lower horizontal line. This intercepted space on the rod is subdivided to read meters and the graduation continued to within a short distance of the bottom. *For further details of the theory of stadia measurements see: Elemente der Vennessungs- Kunde, Bauernfeind, 1873, P- 3 22 ! Handbuch der Vermessungs-Kunde, Jordan, 1888, p. 554; Theory and Practice of Surveying, Johnson, 1898, p. 238; Gillespie's Higher Surveying, Staley, 1897, p. 311; Experimental Study of Field Methods, Smith, Bulletin of University of Wisconsin, Engineering series, Vol. I, No. 5. NO. 4. UAU u a 8 STADIA RODS. APPENDIX 7. A PLANE TABLE MANUAL. 3Ol This graduation is represented by the equation where K x 1 *l I i I ffe p*O \^ /r ^|<; 9 Cj V s ^ j ( i ^ 1 ^ 1 <5 ^ | , R 1 h 3 , "7 S "^x" ^ * r ^ o ^) t/ 3 "^ S't 2 r / / / 6 3 \l >'l i i 1 i *-t 1 !> q ^ ^ ___^ p -5 6 5 .5 I '-- e Fig.l p-**" Fig. 2 Fig. 3 d Fig. 4 BESSEL'S SOLUTION OF THREE-POINT PROBLEM. APPENDIX 7. A PLANE TABLE MANUAL. 313 and the position is determined. If a new triangle of error is formed, it indicates an erroneous estimate, and the operation must be repeated. Orienting by estimation. A small triangle of error is the result of a close orienta- tion, which the topographer endeavors to accomplish at the first trial by taking advan- tage of any range that may exist either of signals or other details already plotted on the sheet. It will serve the same purpose if they are near enough in line to estimate a direction on the sheet to the farthest object, and then to orient by it. The declinatoire may be used, but it is a slow and inaccurate method of orientation. It is employed for this purpose by placing the straight edge of the box containing the needle upon a magnetic meridian, previously traced upon the map, and revolving the table until the needle points to o, or north, on the graduated arc at the end of the box. The magnetic meridian is roughly determined at any well-determined station, when the table is properly oriented by the use of the declinatoire itself, the meridian line being drawn upon the sheet along the straight edge of the box when the needle points to o. Or the table may be oriented by making the straight edge of the box coincide with one of the meridians of the projection and then turning the board until the needle points to the right or left of the zero, according to the amount and direction of the magnetic deviation. BesseVs method by inscribed quadrilateral is the simplest method by construction. The objection to it arises from the fact that in practice the intersection of the construc- tion lines often falls beyond the limit of the board. By this method a quadrilateral is constructed with all the angles in the circumfer- ence of a circle, one diagonal of which passes through the middle one of the three fixed points and the point sought. On this line the alidade is set, the telescope directed to the middle point, and the table is in position. Resection upon the extreme points inter- sects in this line and determines the position of the point sought. Illustration 9, Figs, i, 2, 3, and 4. L,et a b c be the points on the sheet represent- ing the signals A B C on the ground. The table is set up at the point to be determined ( Pock whose existence is doubtfuL. S ZD NO. 26. HYDROGRAPHY, DANGERS, OBSTRUCTIONS CONTINUED Overfalls and Tide Rips Limiting Danger Line Whirlpools and Eddies Wreck Of any kind (or Submerged Derelict) Wreck or Derelict not submerged CaWe (with or without lettering) Current, not tidal, velocity 2 knots f Flood, 1'Aknots J*. * Ebb, 1 knot '** Tidal Currents Flood, 2d hour. \Ebb.3dhour ^^, or- HH-* No bottom at 50 Fathoms So So Depth Curves 1 Fathom or 6 Foot Line 2 Fathom or 12 Foot Line 5 Fathom or 18 Foot Line. 4 Fathom Line 4'A Fathom Line 5 Fathom Line 6 Fathom Line 10 Fathom Line 20 Fathom Line , 30 Fathom Line 40 Fathom Line SO Fathom Line. - NO. 27. HYDROGRAPHY. DANGERS. OBSTRUCTIONS CONTINUED 700 Fathom Line 200 Fathom Line. 300 Fathom Line 500 Fathom Line 1000 Fathom Line. _ _ _ 2000 Fathom Line 3000 Fathom Line Abbreviations relating to Bottoms M. mud, S. sand, G. gravel, Sh. shells, P. pebbles, Sp. specks, CI. clay, St. stones, Co. coral, Oz. ooze, bk. black, wh. white, rd red, yl. yellow, gy. gray, bu. blue, dk. dark, 11. light, gn. green, br. brown, hrd. hard, sft. soft, fne. fine, crs. coarse, rky. rocky, stk. sticky brk. broken, Irg. large, sml. small, stf. stiff, cat. calcareous, dec. decayed, rot. rotten, spk.speckled, fly. flinty, gty. gritty, grd. ground, str. streaky, vol. volcanic. AIDS TO NAVIGATION. ETC. Life-saving Station ^, iss ( T ) [(T) indicates telegraphic connection] Light of any kind (or Lighthouse). jj. Lighthouse, on small scale chart Light Vessel of any kind ^ Light Vessels showing number of masts -^ & sJi. Light with Wireless fi& , 'fyy Light Vessel with Wireless, _ () Light with Submarine Bell. w - Light Vessel with Submarine Bell 4" Light with Submarine Bell and Wireless __.(g) ^ Light Vessel with Submarine Bell and Wireless (T) NO. 28. AIDS TO NAVIGATION. ETC. CONTINUED (Lighted. * * Beacons J \Not lighted-.-. Bn*. 1 i I I I 1 Sectors, shown by dotted lines Abbreviations relating to Lights F. fixed, Fig. flashing, PI. flash, Fls. flashes, Sec. sector, Rev. revolv- ing, E. electric, W. white, R. red, V. varied by, Grp. group, Occ, occulting, Int. intermittent. Alt alternating, m. /n;/es, min. m/nutes, sec. seconds. / Buoy of any kind (or Red Buoy) - B/ac* Striped horizontally 4> Striped vertically Checkered - Buoys < Perch and Square Perc/J and Ball 5 J5 $ Whistling (oruse first four symbols : T : I wrt/i word " whistling ") 414. SeW ( or use first four symbols with jit! word "bell") ^ \Lighted * Spindle or Stake (add word " spindle': I if space allows) Abbreviations relating to Buoys C can, N. nun, S. spar, H. S. horizontal stripes, B. black, R. red, W. white, V. S. vertical stripes, C. green, Y. yellow, Ch. checkered. I Of any kind ( or for large vessels ) i Anchorage J \ For small vessels t- Mooring Buoy * Range or Track Line _ 1 S.JA//O rfcirc 'ANNELS O r WXYZ r WXYZ t^ 1 > 0. ^ o % r^ H^ C ENGRA\ DIVISIOl CAPITOL HARBOR ISLANDS RIVERS SOUNDINGS DIRECTIONS *oints POINTS in u u K O u (0 111 Z z < X o SIVOHS sjntn ^*t_^^ CT5 Q PH >PQRSTL ing *( CO O *o s O 1 1 OP 0) 13 CO -a ^^^^i ^^^^^ r^ ^ L * ^ "g 1 1 5 Jq U o ^^M ^^^^1 k^ | > Z ^N^^^fl ^'^^J ^ NGRA O HH HH HH APITOL ffj O ffl i LANDS VERS )UNDINGS RECTIONS [NTS P OINTS IEKS CREEKS VNELS CHANNELS LB SHOALS FGHIJ 1 H Q O as VJ t i ^-i w CO M Q ^H o m u 3 V m H fcq T M Q Q K O in in o in o tO o in f\4 ^^^ ^^^ H HVi riwcBiwrs'rj * _\s. 4 C- 1 V " L_--= Mocking of Cities. Large Buildings, Suburban Villas and Grounds, Fresh Marsh No. 34 Erosion of Soft fttrntififd Rock and Gulch (Santa Cruz, California) NO. 35. Hill Curves for every 20 feet difference of level. Scale TO; *Q V n O Slope Proportion of Length of Base Length of Base Length of Base CO tf "o cc ID CO O 00 < o NO. 37. 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 12,000(11/95) General Library LD 21 A-50m-l 2 60 University of California (B6221slO)476B Berkeley UNIVERSITY OF CALIFORNIA LIBRARY i -, .,