CHAPTER II.

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