14 CONTENTS, 



CHAPTER II. 



What is AuguJar Aperture . ..... 93 



Angular Aperture ... .... 93 



How Shall we Measure Angular Aperture ... 95 



Object Glasses . 97 



Something Further about Objectives .... 108 



Balsam Apertures 123 



Flatness of Field . , . . . . . . .126 



Mounting of Objectives . . . . . . . 129 



Nomenclature of Objectives 130 



Table of the Magnifying Power of Single Convex Lenses 134 



CHAPTER III. 



Objectives Continued . 137 



Objectives of Lower Balsam Angle 144 



Adjustable Objectives 148 



Eye-Pieces 156 



CHAPTER IV. 



Manipulations Wenham's Reflex Illuminator . . 157 



The Woodward Illuminator ...... 163 



Tolles' Traverse Lens 179 



