Finally, it is the Author’s hope that, by the instrumentality of this volume, he may possibly assist in bringing the Microscope, and its valuable and delightful studies, before the general public in a more familiar, compendious, and economical form than he found it at the period of its publication, so that, in these days of a diffused taste for reading and the spread of cheap publications, he may thus supply further exercise for the intellectual faculties; contribute to the additional amusement and instruction of the family circle, and aid the student of nature in investigating the wonderful and exquisite works of the Almighty. If it shall be the good fortune for this work, which is now confided with great diffidence to the consideration of the public, to succeed, in however slight a degree, in furthering this design, the Author will feel fully repaid for the amount of time and labour expended. LONDON, _May_, 1854. CONTENTS. PART I. PAGE EARLY HISTORY OF THE MICROSCOPE 1 CHAPTER I. LIGHT--ITS PROPAGATION--REFRACTION--SPHERICAL AND CHROMATIC ABERRATION--HUMAN EYE--FORMATION OF IMAGES--VISUAL ANGLE--ABBÉ’S THEORY OF MICROSCOPIC VISION--DEFINITION OF APERTURE--NUMERICAL APERTURE--ABBÉ’S APERTOMETER--STEREOSCOPIC BINOCULAR VISION 12 CHAPTER II. SIMPLE AND COMPOUND MICROSCOPES--EVOLUTION OF THE MODERN ACHROMATIC MICROSCOPE--IMPROVEMENTS IN THE MODERN MICROSCOPE: THE ROSS-JACKSON, POWELL AND LEALAND, BECK’S, BAKER’S, PILLISCHER, ZEISS, LEITZ, WATSON’S, VAN HEURCK’S EDINBURGH STUDENTS’, SWIFT’S, AND BACTERIOLOGICAL 72 CHAPTER III. APPLIED OPTICS--EYE-PIECES--ACHROMATIC OBJECTIVES AND CONDENSERS--MAGNIFYING POWER OF EYE-PIECES AND OBJECTIVES--METHOD OF EMPLOYING THE CONDENSER--ITS ILLUMINATION MIRROR--ACCESSORIES OF THE MICROSCOPE--FINDERS--MICROMETERS--CAMERA-LUCIDA--MICROSCOPE IN POSITION FOR DRAWING--ABBÉ’S TEST-PLATE--MICRO-PHOTOGRAPHY--POLARISATION OF LIGHT--THE MICRO-SPECTROSCOPE 139 CHAPTER IV. PRACTICAL MICROSCOPY--MANIPULATION--MODE OF EMPLOYING THE MICROSCOPE--WORKING ACCESSORIES--METHODS OF PREPARING, HARDENING, STAINING, AND SECTION CUTTING--CUTTING HARD STRUCTURES--INJECTING APPARATUS, MATERIAL, ETC., EMPLOYED IN BACTERIOLOGICAL INVESTIGATIONS--WARM CHAMBERS AND INCUBATORS--PREPARING, MOUNTING, CEMENTING, AND COLLECTING OBJECTS 258 PART II. CHAPTER I.