A HISTORY OF SCIENCE 



lieved in the alchemic theory that metals have " spirits" 

 and various other qualities that do not exist, it is not 

 surprising that he was credulous in the matter of 

 beliefs concerning peculiar phenomena exhibited by 

 them. Furthermore, he undoubtedly fell into the 

 error common to "specialists," or persons working for 

 long periods of time on one subject the error of over- 

 enthusiasm in his subject. He had discovered so many 

 remarkable qualities in the air that it is not surprising 

 to find that he attributed to it many more that he 

 could not demonstrate. 



Boyle's work upon colors, although probably of less 

 importance than his experiments and deductions upon 

 air, show that he was in the van as far as the science of 

 his day was concerned. As he points out, the schools 

 of his time generally taught that " color is a penetrat- 

 ing quality, reaching to the innermost part of the 

 substance," and, as an example of this, sealing-wax 

 was cited, which could be broken into minute bits, 

 each particle retaining the same color as its fellows 

 or the original mass. To refute this theory, and to 

 show instances to the contrary, Boyle, among other 

 things, shows that various colors blue, red, yellow- 

 may be produced upon tempered steel, and yet the 

 metal within u a hair's-breadth of its surface" have 

 none of these colors. Therefore, he was led to believe 

 that color, in opaque bodies at least, is superficial. 



" But before we descend to a more particular con- 

 sideration of our subject," he says, " 'tis proper to 

 observe that colors may be regarded either as a 

 quality residing in bodies to modify light after a 

 particular manner, or else as light itself so modified 



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