CONTENTS. 



BOOK IV. 



INDUCTIVE INVESTIGATION. 

 CHAPTER XVIII. 



OBSERVATION. 



SKCTION P*GF 



1. Observation 399 



2. Distinction of Observation and Experiment . . . . 400 



3. Mental Conditions of Correct Observation 402 



4. Instrumental and Sensual Conditions of Correct Observation . 404 



5. External Conditions of Correct Observation 407 



6. Apparent Sequence of Events 40i) 



7. Negative Arguments from Non-Observation 411 



CHAPTER XIX. 

 BXHttUHXHT, 



1. Experiment 416 



2. Exclusion of Indifferent Circumstances ... .... 419 



422 

 424 

 426 

 428 

 433 



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 ... .... 434 



9. Limits of Experiment . 437 



CHAPTER XX. 

 METHOD OF 



1. Method of Variations . . ........... 439 



2. The Variable and tha Variant ........... 440 



3. Measurement of the Variable ........... 44] 



1. Maintenance of Similar Conditions ..... ; ... 443 



5. Collective Experiments ............. 445 



6. Periodic Variations ............. 447 



7. Combined Periodic Changes ....... .... 450 



8. Principle of Forced Vibrations .... 451 

 . Integrated Variations . . ..... 462 



