CHAPTER IX.--Hypotheses in Physics 127 The Rôle of Experiment and Generalization 127 The Unity of Nature 130 The Rôle of Hypothesis 133 Origin of Mathematical Physics 136
CHAPTER X.--The Theories of Modern Physics 140 Meaning of Physical Theories 140 Physics and Mechanism 144 Present State of the Science 148
CHAPTER XI.--The Calculus of Probabilities 155 Classification of the Problems of Probability 158 Probability in Mathematics 161 Probability in the Physical Sciences 164 Rouge et noir 167 The Probability of Causes 169 The Theory of Errors 170 Conclusions 172
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
