CONTENTS. 



CHAPTEE VIII. Of the Four Methods of Experimental 



Inquiry. 



MM 

 1. Method of Agreement ..... 425 



2. Method of Difference . . . , .428 



3. Mutual relation of these two methods . . . 429 



4. Joint Method of Agreement and Difference . . 433 



5. Method of Residues 436 



6. Method of Concomitant Variations . . . 437 



7. Limitations of this last method .... 443 



CHAPTEE IX. Miscellaneous Examples of the Four Methods. 



1. Liebig's theory of metallic poisons . . . 449 



2. Theory of induced electricity . . . 453 



3. Dr. Wells' theory of dew . . . . .457 



4. Dr. Brown-Sequard's theory of cadaveric rigidity . 465 



5. Examples of the Method of Residues . . . 471 



6. Dr. Whewell's objections to the Four Methods . . 475 



CHAPTEB X. Of Plurality of Causes ; and of the Intermixture 

 of Effects. 



1. One effect may have several causes . . . 482 



2. which is the source of a characteristic imperfection of 



the Method of Agreement .' . . . 483 



3. Plurality of Causes, how ascertained . . . 487 



4. Concurrence of Causes which do not compound their effects 489 



5. Difficulties of the investigation, when causes compound 



their effects ...... 494 



6. Three modes of investigating the laws of complex effects 499 



7. The method of simple observation inapplicable . . 500 



8. The purely experimental method inapplicable . . 501 



CHAPTEE XI. Of the Deductive Method. 



1. First stage; ascertainment of the laws of the separate 



causes by direct induction .... 507 



2. Second stage ; ratiocination from the simple laws of the 



complex cases ...... 512 



3. Third stage ; verification by specific experience . . 514 



