Surveying and Levelling Instruments, Theoretically and Practically Described. For construction, qualities, selection, preservation, adjustments, and uses; with other apparatus and appliances used by civil engineers and surveyors in the field.

CHAPTER II.

Chapter 232 wordsPublic domain

THE TELESCOPE AS A PART OF A SURVEYING INSTRUMENT:--General Description--Qualities--Optical Principles--Refraction of Glass--Limit of Refraction--Reflection--Prisms--Lenses, Convex and Concave--Aberration--Formation of Images--Dispersion-- Achromatism--Curvature of Lenses--Telescopes--Eye-pieces--Powers-- Dynameter--Construction of the Telescope--Diaphragm--Webs--Lines-- Points--Parallax--Examination and Adjustment 24