MISCELLANEOUS. XIII. The Pocket-Sextant-Its Adjustments-Use in Surveying, Measuring Heights and Distances, XV. Marquois Scales and Triangle-Plotting Scale- Mathematical Instruments Of Scales-Geo- XVIII. Observations-Levelling with a Mason's Level- With Boning Staves-Description of a Spirit- Level-Levelling Staves-Method of Levelling with a Spirit-Level-Drawing Sections-Le- velling with a Theodolite-Tracing Contour Lines-French Water-Level-Reflecting-Level 167 XIX. Theory of Levelling-Terrestrial Refraction and Curvature-Levelling by the Mountain Baro- MISCELLANEOUS. XX.-Application of Trigonometry to measuring Heights and Distances-Reduction of Oblique Angles, taken with a Sextant, to the corresponding Horizontal Angles-Portable Trigonometry XXI.-Description and Use of the Large Sextant-Its Adjustments-Artificial Horizon-Method of PLATES. 1.-The Prismatic Compass Page. 1 2.-Method of Surveying a Road by the Compass, and Protracting in the Field 5 3.-Method of Sketching a portion of Ground with the aid of a Compass 9 4.-Finding your Place in a Survey or Sketch when 8.-Method of Surveying a Road with the Theodolite 9.-Form of Register or Field-Book 26 28 10.-Method of conducting a Survey with the Theodolite 45 11. Mr. Howlett's Protractor 57 12. Mr. Metcalf's Protractor 58 13.-Method of Shading Hills; with Ground Plan and Section 64 14.-Specimens of the Vertical and Horizontal Styles of Drawing Hills 66 15.-The Conventional Signs commonly used in Plan Drawing 71 16.-The Pocket-Box Sextant and Reflecting Semicircle 17.-Plan and Field-Book of a Survey with the Chain alone PREFAСЕ. HAVING served more than twenty years in the Royal Staff Corps,* after going through a course of education at the Military College, I venture to recommend the principles and practice of surveying and sketching that I have found most convenient and useful. The design of the following work is to pioneer the way, and enable young officers and students for the military profession to acquire a competent knowledge of the readiest methods of making maps and * A war corps, organized and armed as a body of infantry, but trained to the duties of Field-engineering. The officers were mounted, and expected to perform the services of the Quartermaster-General's Department-the Field-officers ranking as Assistants, and the Captains and Subalterns as Deputy-Assistants; receiving, when in the field, forage and other allowances according to their staff-rank. The qualification for an officer was a military education, and four-fifths of the soldiers were mechanics. This corps was not broken up until many years after the termination of the late war, its services having been made available in the colonies. plans, taking topographical sketches, &c. &c., unaided by an instructor: with this object, the plainest rules and examples are given, in order that no part of the Treatise should be found too difficult for a beginner of ordinary diligence and ability to understand and follow. My collection of memoranda on Military Surveying not having been originally designed as a classbook, but rather to smooth the way for young officers, and induce them to cultivate an acquirement not only useful to the service, but often highly advantageous to themselves, the arrangement of the subjects was not according to the method of instruction that I would recommend teachers to pursue. When subsequently the work was adopted by two of our military colleges, it became a question whether a material alteration ought not to be made; but, considering that no course which I could lay down would be implicitly followed by any instructor, and with the satisfaction of believing the former arrangement to have been useful, I have forborne to make any very important changes in the present edition. The order of instruction that I would recommend in military colleges and schools is as follows: |