CONTENTS. XV 



CHAPTER VII I. Of the Four Method* of Experimental 

 Inquiry. 



PAGE 



1. Method of Agreement . :*,' 450 



2. Method of Difference . . . . . . 454 



3. Mutual relation of these two methods . . . . 456 



4. Joint Method of Agreement and Difference . . 460 



5. Method of Residues . . . . 464 



6. Method of Concomitant Variations . . 466 



7. Limitations of this last method .... 473 



CHAPTER IX. Miscellaneous Examples of the Four Methods. 



1. Liebig*s theory of metallic poisons . . . . 480 



2. how far a perfect example .... 484 



3. Theory of induced electricity .... 485 



4. Dr. Wells' theory of dew . . ... . 490 



5. Examples of the Method of Residues . . . 501 



CHAPTER X. Of Plurality of Causes; and of the Intermix- 

 ture of Effects. 



1 . One effect may have several causes . . . 506 



2. which is the source of a characteristic imperfection of the 



Method of Agreement ..... 507 



3. Plurality of Causes, how ascertained . . .513 



4. Concurrence of causes which do not compound their effects 514 



5. Difficulties of the investigation, when causes compound 



their effects . . . . . .519 



6. Three modes of investigating the laws of complex effects . 524 



7. The method of simple observation inapplicable . . 526 



8. The purely experimental method inapplicable . . 528 



CHAPTER XI. Of the Deductive Method. 



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



causes by direct induction ..... 534 



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



complex cases . . . . . . 541 



3. Third stage ; verification by specific experience . . 543 



