the aim of the author has been to explain clearly the principles involved, and, as a general rule, to give only those methods for practice which he deems the best. By pursuing this course he has kept the volume within moderate limits, and has presented the subject in such a form as will, he trusts, meet the wants of teachers generally, as well as of very many practical surveyors.

The tables appended to this treatise have been prepared with much care. That of Latitudes and Departures will be found to be more concise than those usually given, and, being extended to four decimal places, will enable the calculator to give greater accuracy to his work. The table of Logarithms of Numberg has been carefully compared with those of Babbage, Hutton, and other standard authors. That of Sines and Tangents was taken from Hutton, and compared with other seven-decimal tables. Besides these, there is a table of Natural Sines and Cosines to every minute, and one of Chords to every five minutes, of the quadrant.