334 CREATIVE SCIENCE 



noon sunlight reflected from the windows of the Luxembourg Palace. 

 He observed a totally unexpected variation of the intensity of the 

 transmitted light with the orientation of the crystal held in his hand. 

 The role of chance here is enormous: for example, had the angle 

 Malus-window-sun been much different, there would have been no 

 effect for him to observe. On the other hand, in the happy circum- 

 stances which did exist this was a focal discovery: it manifested it- 

 self in the light to which Malus' eye was directed. 



Priestley prepared gases by heating strongly various materials 

 selected more or less at random. Given chemical thought of the time, 

 Priestley examined each gas specimen for certain "qualities"— of 

 which ability to support combustion was one. A great display of such 

 ability in one particular gas specimen ultimately led Priestley to the 

 discovery of oxygen. The original discovery was, as Priestley himself 

 regarded it, quite accidental. But, the quality concerned lying within 

 the purview of attention, it plainly was a focal discovery. 



Roentgen accidentally disco\^ered X-rays by the fluorescence they 

 produce. Though wholly unanticipated, the discovery was focal. 

 Roentgen was using a fluorescent screen as a radiation detector, and 

 what he noticed was that the screen fluoresced when no familiar 

 radiation was reaching it. Becquerel's discovery of radioactivity is 

 entirely similar. \\^hile using photographic plates to detect supposed 

 X-rays emitted by uranium compounds, Becquerel found one plate 

 very heavily blackened when he had not expected it to be so. Ray- 

 leigh finds the first clue to the discov^ery of an unthought-of element, 

 in a minute discrepancy in the densities of samples of "pure" nitro- 

 gen. But these densities were, of course, the direct focus of Ray- 

 leigh's attention. 



May it be that focal discoveries present no problem? After all, the 

 unexpected occurrence manifests itself as a surprising value of some 

 quality which is already under direct examination. How can one then 

 possibly fail to observe the phenomenon? So stated, the question de- 

 nies the problem. For the whole difficulty of accidental discovery is 

 just the recognition that a surprising manifestation is a phenomenon. 

 Examples of focal discoveries that were missed testify how very real 

 that difficultv is. 



Mitscherlich, skillful chemical crystallographer, examines racemic 

 acid with a \'iew to describing its crystal habit. The shape of these 

 crystals is the focus of his attention, but he saw nothing whatever 



