Chapter Xii.--Optics and Electricity 174

Fresnel's Theory 174 Maxwell's Theory 175 The Mechanical Explanation of Physical Phenomena 177

CHAPTER XIII.--Electrodynamics 184 Ampère's Theory 184 Closed Currents 185 Action of a Closed Current on a Portion of Current 186 Continuous Rotations 187 Mutual Action of Two Open Currents 189 Induction 190 Theory of Helmholtz 191 Difficulties Raised by these Theories 193 Maxwell's Theory 193 Rowland's Experiment 194 The Theory of Lorentz 196

THE VALUE OF SCIENCE

Translator's Introduction 201 Does the Scientist Create Science? 201 The Mind Dispelling Optical Illusions 202 Euclid not Necessary 202 Without Hypotheses, no Science 203 What Outcome? 203 Introduction 205