Electrotyped by SMITH & MCDOUGAL, 82 Beekman Street, New York.

PREFACE.

D

AVIES' Elements of Surveying, first published in 1830, was designed as a text-book for the pupils of the U. S. Military Academy, and in its preparation little regard was had to the supposed wants of other institutions.

The work was, however, received by the public with more favor than was anticipated, and soon became a leading text-book in Colleges, Academies, and the higher grade of Schools. For the purpose of adapting it more fully to the requirements of these institutions, the author made many changes in successive editions, and gave it his final revision in 1870.

In the present edition, while the admirable features which have hitherto commended the work so highly to institutions of learning and to practical surveyors have been retained, some of the topics have been abridged in treatment and some enlarged, others have been added, and the whole has been arranged in the order of progressive development.

It has been the intention to begin with the very elements of the subject and to combine those elements in the simplest manner, so as to render the higher branches of Plane Surveying comparatively easy. The necessary principles of logarithms and plane trigonometry are given, and their mode of application shown. All the instruments needed for plotting have been carefully described; and the uses of those required for the measurement of angles are fully explained.

In the section on Magnetic Declination or Variation of the Needle, papers of the U. S. Coast and Geodetic Survey have been largely used. From them have been taken :-tables of annual changes in declination, and for computing the declination at any epoch, at various places in the United States, which will be found

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