KF 8301 HARVARD Entered, according to the Act of Congress, in the year 1855, by WILLIAM MITCHELL GILLESPIE, District of New-York. PREFACE. LAND-SURVEYING is perhaps the oldest of the mathematical arts. Indeed, Geometry itself, as its name—“Land-measuring”-implies, is said to have arisen from the efforts of the Egyptian sages to recover and to fix the land-marks annually swept away by the inundations of the Nile. The art is also one of the most important at the present day, as determining the title to land, the foundation of the whole wealth of the world. It is besides one of the most useful as a study, from its striking exemplifications of the practical bearings of abstract mathematics. But, strangely enough, Surveying has never yet been reduced to a systematic and symmetric whole. To effect this, by basing the art on a few simple principles, and tracing them out into their complicated ramifications and varied applications (which extend from the measurement of “a mowing lot " to that of the Heavens), has been the earnest endeavor of thepresent writer. The work, in its inception, grew out of the author's own needs. Teaching Surveying, as preliminary to a course of Civil Engineering, he found none of the books in use (though very excellent in many respects) suited to his purpose. He was therefore compelled to teach the subject by a combination of familiar lectures on its principles and exemplifications of its practice. His notes continually swelling in bulk, gradually became systematized in nearly their present form, and in 1851 he printed a synopsis of them for the use of his classes. His system has thus been fully tested, and the present volume is the result. A double object has been kept in view in its preparation ; viz. to produce a very plain introduction to the subject, easy to be mastered by the young scholar or the practical man of little previous acquirement, the only pre-requisites being arithmetic and a little geometry; and at the same time to make the instruction of such a character as to lay a foundation broad enough and deep enough for the most complete superstructure which the professional student may subsequently wish to raise upon it For the convenience of those wishing to make a hasty examination of the book, a summary of some of its leading points and most peculiar features will here be given. I. All the operations of Surveying are deduced from only five simple principles. These principles are enunciated and illustrated in Chapter 1, of Part I. They will be at once recognized by the Geometer as familiar systems of " Co-ordinates;" but they were not here arbitrarily assumed in advance. They were arrived at most practically by analyzing all the numerous and incongruous methods and contrivances employed in Surveying, and rejecting, one after another, all extraneous and non-essential portions, thus reducing down the operations, one by one and step by step, to more and more general and comprehensive laws, till at last, by continual elimination, they were unexpectedly resolved into these few and simple principles; upon which it is here attempted to build up a symmetrical system. II. The three operations common to all kinds of Land-surveying, viz. Making the Measurements, Drawing the Maps, and Calculating the Contents, are fully examined in advance, in Part I, Chapters 2, 3, 4, so that when the various methods of Surveying are subsequently taken up, only the few new points which are peculiar to each, require to be explained. Each kind of Surveying, founded on one of the five fundamental prin. ciples, is then explained in its turn, in the successive Parts, and each carefully kept distinct from the rest. III. A complete system of Surveying with only a chain, a rope, or IV. The various Problems in Chapter 5, of Part II, will be found V. In Compass Surveying, Part III, the Field work, in Chapter 3, VI. The effects of the continual change in the Variation of the mag- VII. In Part IV, in Chapter 1, the Transit and Theodolite are VIII. In Part VII, will be found all the best methods of overcoming IX. Part XI contains a very complete and systematic collection of X. The Methods of Surveying the Public Lands of the United States, XI. The Tables comprise a Traverse Table, computed for this volume, XII. The great number of engraved illustrations, most of them orig- XIII. The practical details, and hints to the young Surveyor, have Should any important error, either of printer or author, be discovered The present volume will be followed by another on LEVELLING AND |