CHAPTER I.

MICROSCOPES AND THEIR MANAGEMENT.

Powers that are most serviceable--Estimated by Focal length--Length of Body of Microscope and its Effects--Popular Errors about Great Magnification--Modes of Stating Magnifying Power--use of an "Erector"--Power of various Objectives with different Eye-pieces--Examination of Surface Markings--Methods of Illumination--Direct and Oblique Light--Stage Aperture--Dark-ground Illumination--Mode of Softening Light--Microscope Lamps--Care of the Eyes