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THE following pages were written at the request of the Publisher, in consequence of the very numerous applications he had received for a book upon this subject. In doing this, it was suggested that, in addition to explaining the method of taking levels in the field, and afterwards transferring them to paper in the form of a section, I should add an example of their application to practical purposes: I have accordingly inserted an example of road-work, wherein the necessary calculations of earth-work are shown, and worked out in full, both by the Prismoidal Formula, and the shorter process by the use of the Tables of Mr. Macneill; * and, as in a manner connected with the subject, it was also suggested that I should add some particulars upon the choice of a line of direction through a country for a road or railroad, preparatory to taking levels. In conclusion, I have given an abstract of the late Mr. Telford's rules for making and repairing roads, as contained in full in the valuable work of "Sir Henry Parnell on Roads."
An Appendix is added, with permission, containing a description of Macneill's instrument for the purpose of ascertaining the comparative merits of roads, and the state of repair in which they are kept.
F. W. S.
*Now Sir John Macneill.
ADVERTISEMENT TO THE FOURTH EDITION.
THE previous editions being out of print, a fourth is now issued, with the addition of Mr. Law's method of setting out Railway Curves, together with a very valuable and concise work on Field. Practice, by Mr. Trautwine (a Civil Engineer of the United States), which, as an Appendix, will add much to the utility of the work. J. W.
August 25, 1855.