THE SCIENCE OF MICROSCOrY. 329 



failures and errors of observation caused by imperfect instruments, 

 or unskilful use of them, and that the consideration of the 

 circumstances and causes of past failure has supplied both the 

 motive of interest and the suggestion of a more successful 

 procedure. Speaking generally the motive to re-observation and 

 reconsideration of our facts lies, not so much in doubting what we 

 see, as in the distrust of a number of contradictory explanations 

 which sends us back again to our starting point. Yet unless the 

 new search be guided by scientific rules, there seems little 

 prospect of a more correct result or any warrant of certainty in 

 substituting new impressions for old. The absence, addition, or 

 falsification of detail in the microscope image which no mere 

 looking at will discover or even bring under suspicion, will remain 

 undiscovered by every observer who is not guided by the 

 consideration that such things are not only possible, but have 

 been demonstrated by optical analysis of the image of the simplest 

 objects, and must occur in a far more illusive form in the images 

 of more complex objects. These very illusions moreover, when 

 brought under proper optical analysis prove more forcibly than 

 anything else the ahsolute precisioro and interpreting power of a real 

 science of microscopy , though the vivid clearness of their appearance 

 in the microscope image may confirm the observer in his erroneous 

 interpretation, who is not prepared to credit the existence of that 

 which he does ncc see, or to accept a theoretical explanation where 

 none seems to be required, because the image is so clearly seen. 



Nevertheless, the antagonism between theory and practice, seeing 

 and believing, is not one of principle but of relative knowledge. 

 And since every revelation of the microscope comes by mental 

 insight based on the warrant of optical science, it seems scarcely 

 reasonable to ignore the application of optical law of a higher order 

 when it leads to a more perfect revelation, because the observer 

 may not be prepared for it so long as he clings to his wonted 

 interpretation. With whatever grade of reasoning observation the 

 individual microscopist may profess himself satisfied, it is plainly 



