A HISTORY OF SCIENCE 



in the form of spectacles, cannot be proven. Smith 

 has determined that as early as the opening years of 

 tne fourteenth century such lenses were in use, but 

 this proves nothing as regards Bacon's connection 

 with their invention. The knowledge of lenses seems to 

 be very ancient, if we may judge from the convex lens 

 of rock crystal found by Layard in his excavations 

 at Nimrud. There is nothing to show, however, that 

 the ancients ever thought of using them to correct 

 defects of vision. Neither, apparently, is it feasible to 

 determine whether the idea of such an application 

 originated with Bacon. 



Another mechanical discovery about which there 

 has been a great deal of discussion is Bacon's supposed 

 invention of gunpowder. It appears that in a certain 

 passage of his work he describes the process of making 

 a substance that is, in effect, ordinary gunpowder; 

 but it is more than doubtful whether he understood 

 the properties of the substance he describes. It is 

 fairly well established, however, that in Bacon's 

 time gunpowder was known to the Arabs, so that it 

 should not be surprising to find references made 

 to it in Bacon's work, since there is reason to be- 

 lieve that he constantly consulted Arabian writ- 

 ings. 



The great merit of Bacon's work, however, depends 

 on the principles taught as regards experiment and 

 the observation of nature, rather than on any single 

 invention. He had the all-important idea of breaking 

 with tradition. He championed unfettered inquiry in 

 every field of thought. He had the instinct of a 

 scientific worker a rare instinct indeed in that age. 



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