14 CONTENTS. 



CHAPTEE II. 



What is Augnlar 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 . . . . . 530 



Table of the Magnifying Power of Single Convex Lenses 134 ' 



CHAPTER III. 



Objectives Continued 137 



Objectives of Lower Balsam Angle . . . .144 



Adjustable Objectives . . , . . . 345 



Eye-Pieces 156 



CHAPTER IV. 



Manipulations Wenham's Reflex Illuminator . . 157 



The Woodward Illuminator ...... 163 



Tolles' Traverse Lens ... 179 



