xl CONTENTS. 



BOOK IV. 



INDUCTIVE INVESTIGATION. 

 CHAPTER XVIII. 



OBSERVATION. 

 SECTION PAGE 



1. Observation 399 



2. Distinction of Observation and Experiment 400 



3. Tilental 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 . . 40.-^ 



7. Negative Arguments from Non-Observation 411 



CHAPTER XIX. 



EXPEUIMENT. 



1. Experiment 416 



2. Exclusion of Indifferent Circumstances 419 



3. Simplification of Experiments 422 



4. Failure in the Simplification of Experiments 424 



5. Kemoval of Usual Conditions 42(3 



6. Interference of Unsusjiected Conditions 4"i8 



7. Blind or Test Experiments 433 



8. Negative Results of Experiment 434 



9. Liudts of Experiment '(37 



CHAPTER XX. 



METHOD OF VARIATIONS. 



1. Method of Variations 439 



2. The Variable and the Variant 440 



3. Measurement of th'^ Variable 441 



4. Maintenance of Similar Conditions 443 



.5. Collective Experiments 445 



6. Periodic Variations 447 



7. Combined Periodic Cliiiiigcs 4.50 



8. Principle of Forced Vibrations 4.'il 



9. Integrated Variations 452 



