F222 BARCROCOLLEGE LIBRARY Education duplicats money ENTERED, according to Act of Congress, in the year 1870, BY D. APPLETON & COMPANY, In the Office of the Librarian of Congress, at Washington.. PREFACE. THIS volume, announced several years ago as bein preparation to follow the author's Land Surveying, wa at the time of his death unfinished. In preparing it fo press, the editor has endeavored to carry out, as far as sible, the plan already laid down. A considerable part volume has been given by the author, in the form of lec to the civil engineering classes in Union College, and been printed from the original manuscript. The best authors on the subjects treated have been sulted, in order to render the work as complete as pos The principal authorities are the following: Begat, Bo Breton, Chauvenet, Fenwick, Frome, Gurley, Guyot, Ja Lee, Narrien, Puissant, Salneuve, Simms, Smith, Stephe Wiesbach, Williams, and the papers of the United S Coast Survey. Wherever it has been necessary to refer to the eleme principles of surveying, reference has been made to Gille Land Surveying (designated as L. S. for brevity), and numbers of the articles referred to are enclosed in parent UNION COLLEGE, |