: . : ,;.:. >,;,-y : STANLEYS SURVEYING INSTRUMENTS * <^ SURVEYING AND LEVELLING INSTRUMENTS THEORETICALLY AND PRACTICALLY DESCRIBED FOR CONSTRUCTION, QUALITIES, SELECTION, PRESERVATION, ADJUSTMENTS, AND USES; WITH OTHER APPARATUS AND APPLIANCES USED BY CIVIL ENGINEERS AND SURVEYORS BY WILLIAM FORD STANLEY Optician, Manufacturer of Surveying and Drawing Instruments, Author of a Treatise on Drawing Instruments, Properties and Motions of Fluids, &c. LONDON: E. & F. N. SPON, 125 STRAND NEW YORK: 446 BROOME STREET AND OF THE AUTHOR, GREAT TURNSTILE, HOLBORN, LONDON, VV.C. 1890 PREFACE NOTES were taken for many years before the production of this work of queries that came before the author for reply relative to functional parts of surveying instru- ments. These bore most frequently reference to optical and magnetical subjects and to the qualities and action of spirit level tubes, also occasionally to graduation and the qualities of clamp and tangent motions. It was therefore thought that it would be useful to give notes upon these subjects in detail as far as possible in early chapters. As the work proceeded it was found that this plan saved much space, in avoiding the necessity for separate descriptions when complex instruments were afterwards described. To show the state of the art and render the work useful, it was necessary that the structure of surveying instruments should be given With sufficient detail to be worked out by the skilful manufacturer. Beyond this it was thought to be most important that the professional man, who must have limited experience of the qualities of workmanship, should be supplied with as many simple tests as possible for assuring the qualities of the instru- ments he might purchase or use, with details also of their adjustments. This matter is therefore carried into detail for one instrument at least of each class, as very little general information is to be found on the subject IV PREFACE. in our literature. In fact, large groups of instruments in extensive use, such as those for mining surveying, and subtense instruments, have remained heretofore nearly undescribed in our language. The technical principles followed in working out details in these pages are given by illustrations of such parts of important instruments as present any difficulty of observation from an exterior view of the engraving of the entire instrument. The plans of construction thought to be the best are selected for illustration. Certain constructions that are liable to failure are pointed out. Many recent improvements in instruments are recognized and some are suggested, but no attempt has been made to record the little differences of construction, often meritorious, which give only a certain amount of style to the work of each country and of each individual. Upon this point it must occur that the work done in any shop must vary from other work according to the skill and judgment of the master. It is intended, there- fore, that distinctly typical instruments only should be described, in a manner that details may be worked out therefrom. To make this matter as clear as possible, with few exceptions these pages were written in the presence of the instruments described, and the illus- trations, when not taken directly from the instruments, were taken from workshop drawings to a reduced scale. In practice it is found that instruments performing similar functions may be very much varied in construc- tion, bearing reference frequently to the conditions under which they are to be used. The same may be said of the functional parts of instruments. We may also PREFACE. V observe that English instruments differ in detail from foreign ones, and upon this point there is no doubt much may be learned by comparison of some details of English and foreign work, although our own is admitted to rank high. Comparisons are therefore freely made in the following pages, and suggestions offered after study abroad of foreign work and careful inspection of nearly the whole literature upon the subject, in which it is very observable that Continental books, treating of parts of the subject, are much in advance of our own. The surveying instruments described in these pages are nearly limited to those used in the field. Instru- ments for plan drawing and calculation of areas, which the surveyor uses in the office, have been described in the author's work on drawing instruments (sixth edition), to which this is intended to be the complement of the subject. To render the work as complete as possible it was thought to be necessary to give briefly the manner of using many instruments in practical surveying. This part of the subject, from the author's very limited ex- perience in the field, is largely taken from inspection of the best works on surveying. The author, however, is very pleased to acknowledge the kindness of many pro- fessional friends for assistance on this and many other points, and for historical notes. For the description of the 36 -inch theodolite, given in chapter VII., the author is indebted to the late Col. A. Strange, F.R.S., who gave every detail of his design and discussed many points. The author is also indebted to Mr. Thomas Gushing, F.R.A.S., Inspector of Scientific Instruments VI PREFACE. for India, who has given information and his opinions upon many subjects from his large practical experience. Also to Prof. George Fuller, C.E., who has kindly read proofs, examined formulae, and made some technical points to Mr. Inst. clearer. Also W. N. Bakewell, M. C. E. ; A. R.E. Major -General De Lisle, ; Right Hon. Lord Rayleigh, F.R.S., for assistance on several technical points. In this first edition, entirely from manuscript, there will no doubt be errors and omissions; therefore the author will feel obliged by the receipt of any notes that he may make use of for future corrections, should another edition be demanded. CONTENTS CHAPTER I. PAGE INTRODUCTION: Historical Sketch Classification of the Subject Purposes and Qualities of Instruments Workmanship Metals Framing Tools Axes of Instruments Soldering Finishing Bronzing Lacquering Graduating Engraving Glass - work Wood - work Lubrication Preservation of Instruments Packing ........ i CHAPTER II. THE TELESCOPE AS A PART OF A SURVEYING INSTRUMENT : General Description Qualities; Optical Principles Re- fraction of Glass Limit of Refraction Reflection Prisms Lenses, Convex and Concave Aberration Formation of Images Dispersion Achromatism Curvature of Lenses Telescopes Eye-pieces Powers Dynameter Construction of the Telescope, Diaphragm Webs Parallax Examination and Adjustment 24 CHAPTER III. THE MAGNETIC COMPASS AS A PART OF A SURVEYING INSTRU- MENT OR SEPARATELY: Broad and Edge -bar Needles Manufacture of the Needle Magnetization Suspension Dip and Adjustment Lifting Inclination Declination Variation Correction Compass-boxes Preservation of Magnetism Description of Compasses Ring Compasses Trough Compasses Prismatic Compasses Stand Survey- ing with Compass Pocket Compasses . '. 58 Vlll CONTENTS. CHAPTER IV. PAGE LEVELS : Methods of Ascertaining Level Tubes Manufacture Curvature Sensitiveness Testing Reading Surveyors' Levels Y-Level Parallel Plates Adjustments of Y-Levels Suggested Improvements Dumpy Level Tripod Stands Adjustment of Dumpy Collimator Improvements in Dumpy Level Tribrach Head Diaphragms Cushing's Level Cooke's Level Cheap Forms of Level ... 85 CHAPTER V. LEVELLING STAVES : Construction Various Readings Dis- cussed Sopwith's Field's --Strange's Stanley's New Metrical Simple Construction Mining Staff Papering Levelling Staves Preservation Packing Pads Staff Plate Staff Level Practice of Levelling Index of Bubble Lamp Curvature Corrections Station Pegs Refinement of Levelling Levelling Books Ink Bottle, etc. .139 CHAPTER VI. DIVISION OF THE CIRCLE AND METHODS EMPLOYED IN TAKING ANGLES : Dividing Engine Surfaces for Graduation Vernier Various Sections Reading Microscopes Shades Micrometers Clamp and Tangent Motions of Limbs of Axes Use and Wear Difference of Hypotenuse and Base 168 CHAPTER VII. THEODOLITES: 5-inch and 6-inch Transits Construction Additional Parts Plummet Striding Level Lamp Adjustment of Axis over a Point Burt's Solar Attachment 8-inch and Larger Instruments Everest's Tribrach Plain Theodolites French Instruments Everest's Theodo- lite Stanley's New Model Mechanical Tribrach Stage CONTENTS. IX PAGE Altazimuth Theodolite Great Indian Theodolite Simple Theodolite Mountain Theodolite Examination and Adjustments . 202 CHAPTER VIII. MINING SURVEY INSTRUMENTS : Circumferenters Plain Miner's Dial Sights Tripod Stand Adjustments Henderson's Dial Lean's Dial Adjustments Hedley's Dial Additional Telescope Improved Hedley Tribrach and Ball Adjust- ment Reflectors Continental Forms Theodolite Souterrain Tripod Tables Stanley's Mining Theodolite Pastorelli's, Hoffmann's, and Doering's Adjustable Tripod Heads Mining Transit Theodolites Stanley's Prismatic Mining Compass Hanging Dial Hanging Clinometer Semi- circumferenter Mining Lamps ...... 276 CHAPTER IX. INSTRUMENTS TO MEASURE SUBTENSE OR TANGENTIAL ANGLES TO ASCERTAIN DISTANCES : Historical Notes of the Method Principles Involved Stadia Measurements, Direct and by the Ordinary Telescope Corrections for Refraction of the Object-glass Anallatic Telescope of Porro The Cleps - Tacheometers Stadia Field-book Wagner - Fennel Tacheometer Co - ordinate Protractor Omnimeter Field - book Bakewell's Subtense Arrangement . 318 CHAPTER X. INSTRUMENTS OF REFLECTION : Octant or Quadrant Reflecting Circle Sextant Principle Parallax