CONTENTS, 



BOOK IV. 



INDUCTIVE INVESTIGATION. 

 CHAPTEll XVIII. 



OBSERVATION. 



PAGE 

 CTION j 



1. Observation 



2. Distinction of Observation and Experiment . 



3. Mental Conditions of Correct Observation . 



4. Instrumental and Sensual Conditions of Correct Observation . 7 



5. External Conditions of Correct Observation . 



6. Apparent Sequence of Events . . 



7. Negative Arguments founded on the Non-Observation c 



Phenomena 



CHAPTEll XIX. 



EXPERIMENT. 



22 



1. Experiment . ~a 



2. Exclusion of Indifferent Circumstances 



3. Simplification of Experiments 



4. Failure in the Simplification of Experiments 



5. Removal of Usual Conditions 



6. Interference of Unsuspected Conditions 



7. Blind or Test Experiments 



8. Negative Results of Experiment . 



9. Limits of Experiment 



CHAPTER XX. 



METHOD OP VARIATIONS. 



50 



1. Method of Variations 51 



2. The Variable and the Variant 53 



3. Measurement of the Variable . 55 



4. Maintenance of Similar Conditions . 57 



5. Collective Experiments G1 



6. Periodic Variations . ^3 

 1. Combined Periodic Changes 65 



8. Principle of Forced Vibrations G7 



9. Integrated Variations 



