xl CONTENTS. 



BOOK IV. -..- ... 



INDUCTIVE INVESTIGATION. 

 CHAPTER XVIII. 



OBSERVATION. 

 SECTION PAOF 



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 403 



7. Negative Arguments from Non-Observation 411 



CH AFTER XIX. 



KXTKKIMENT. 



1. Experiment 416 



2. Exclusion of Indifferent Circumstances 419 



3. Simplification of Experiments 422 



4. Failure in the Simplification of Experiments 424 



5. Removal of Usual Conditions 426 



6. Interference of Unsuspected Conditions 428 



7. Blind or Test Experiments 433 



8. Negative Results of Experiment 434 



9. Limits of Experiment . 437 



CHAPTER XX. 



METHOD OF 



1. Method of Variations . . ... . . : .''... . . . 439 



2. The Variable and the Variant . . . /- . . . . . . .440 



3. Measurement of the Variable . ; ; . - ; ',. .... 441 



I-. Maintenance of Similar Conditions ......... 443 



6. Collective Experiments ............. 445 



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



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



8. Principle of Forced Vibrations ........... 451 



9. Integrated Variations ...... .462 



