I. For the purpose of study the subject of Elementary Survey ing may be divided into the following parts: (1) Coordinates of surveying, which are the magnitudes which serve to fix the position of a point, — ih space, on a surface, or on a line. (2) Surveying instruments, by means of which the magnitudes are measured. (3) Errors of measurement. (4) Methods of surveying, which deal with the practical application of systems of coordinates, either singly or in combination, through the use of various surveying instruments. (5) Computing and mapping, by which the measurements are combined and the results presented for convenient use.