460 SPECIAL METHODS OF DISCOVERY. 



of the most distant nebulae might probably be resolved into 

 stars if our telescopes 'were sufficiently powerful. And, 

 third, in many cases we either do not know when to look, 

 where to look, or what to look for. 



Arising from these two fundamental principles of dis- 

 covery are two general modes of procedure, by means of 

 which the high priests of demonstrable truth unfold to 

 mankind the continuous revelation of nature, and advance 

 towards acquiring unknown truths, viz., by induction and 

 deduction. The inductive method consists in evolving, by 

 a process of inference, a knowledge of causes by means 

 of a previous knowledge of their effects, and is used for 

 discovering, detecting, and determining causes, and for 

 analysing phenomena and substances. The deductive one 

 consists in imagining effects from a previous acquaintance 

 with their causes, and then testing our suppositions by 

 experiment ; it is employed for ascertaining new effects, 

 and for synthetically discovering new compounds and phe- 

 nomena, 



In the investigation of compound substances by means 

 of chemical analysis, we work according to the inductive 

 method of division and exclusion, drawing new knowledge 

 in the form of observations, inferences, or conclusions, 

 and raising new hypotheses as we proceed. We first apply 

 group tests, and exclude one by one the various classes of 

 bodies to which the substance present does not belong. 

 Having at length found a group which contains the sub- 

 stance, we continue to divide and exclude by appropriate 

 tests all the various bodies belonging to that group until 

 we can divide and exclude no more, and then ascertain by 

 means of suitable tests what the individual substance is. 

 In the scientific investigation of complex phenomena and 

 their relations, we proceed in a similar analytic or inductive 

 manner, extracting new answers, and raising new questions 



