94 SCIENTIFIC INVESTIGATION 



But another man, who has devoted a great deal of time 

 and attention to the subject, and availed himself of the 

 most powerful telescopes and the results of the observa- 

 tions of others, declares that in his opinion it is probably 

 composed of materials very simitar to those of which 

 our own earth is made up : and that is also only an hy- 

 pothesis. But I need not tell you that there is an enor- 

 mous difference in the value of the two hypotheses. 

 That one which is based on sound scientific knowledge 

 is sure to have a corresponding value ; and that which 

 is a mere hasty random guess is likely to have but little 

 value. Every great step in our progress in discovering 

 causes has been made in exactly the same way as that 

 which I have detailed to you. A person observing the 

 occurrence of certain facts and phenomena asks, nat- 

 urally enough, what process, what kind of operation 

 known to occur in Nature applied to the particular 

 case, will unravel and explain the mystery ? Hence you 

 have the scientific hypothesis ; and its value will be pro- 

 portionate to the care and completeness with which its 

 basis had been tested and verified. It is in these matters 

 as in the commonest affairs of practical life : the guess of 

 the fool will be folly, while the guess of the wise man 

 will contain wisdom. In all cases, you see that the value 

 of the result depends on the patience and faithfulness 

 with which the investigator applies to his hypothesis 

 every possible kind of verification. 



