524 SPECIAL METHODS OF DISCOVERY. 



/. By assuming the existence of complete homologous 

 series. The assumption of the truth of Bode's law, and 

 of the necessity of another planet to fill the missing space 

 in the series, led, as we have already shown, 1 to the dis- 

 covery of all the asteroids. That of complete homologous 

 series in organic chemistry led to the discovery of a whole 

 multitude of compound substances, including cyanides, 

 ethers, alcohols, fatty acids, paraffins, compounds of monad, 

 dyad, triad, tetrad, and hexad compound radicals ; ben- 

 zene, napthalene, and anthracine compounds, and nume- 

 rous other substances ; and the number of compound 

 bodies which might be discovered in order to complete 

 homologous series, even by the union of one class of sub- 

 stances only, has been shown by Berthelot to be immense. 2 

 Wilde has recently, by means of the hypothesis of homo- 

 logous series, predicted the future discovery of a number 

 of new elementary substances. 3 



CHAPTER LV. 



DISCOVERY BY MEANS OF NEW EXPERIMENTS AND METHODS 

 OF WORKING. 



THIS method is also based upon the principle that new 

 substances and new combinations of causes and conditions 

 produce new effects. The method may be divided into 

 invention of inductive experiments to find the causes of 

 given effects, and of deductive ones to find the effects of 

 given causes. It may also be divided into several more 



1 See pp. 488-510. 2 See pp. 30, 31. 



8 See Proceedings of the Manchester Philosophical Society, April 30, 

 1878. 



