ROGER BACON. 83 



the most unlikely that he should have known as much about 

 the elements as all this, but the fact remains that the idea of 

 chemical evolution is implied in the words we have quoted. 

 The only explanation we can suggest to account for such a 

 pregnant idea is that, as the alchemists sought to effect 

 transformations of all kinds and often succeeded, Roger was 

 led to the conception that nature could transform everything, 

 and at the beginning of things had compounded various 

 elements out of one a wonderful conception ! Need we 

 mention that Francis was unable to appreciate chemistry and 

 its founders ? his knowledge in this respect stopped at 

 boiling sandstone soft ! a comical experiment which no 

 chemist in the world ever accomplished before or since. 



F. Roger was also a true PHYSICIST of high order too. 

 Before we see his more important work as such, we may note 

 in passing that he mentions a phenomenon which seems to 

 have been observed and recorded for the first time by him, 

 viz. the warm temperature of mines (a fact denied by Francis 

 Bacon), and the constancy of that warmth.* " In mineralium 

 vero locis invenitur calidas semper constans." We state 

 this detail for the mere purpose of showing the varied range 

 of his researches. It was in optics, however, that he proved 

 his competence. He treats of this branch in several works. In 

 >u Perspectives " he describes the eye and the sense of sight ; 

 explains the anatomy and physiology of the eye ; expounds 

 the laws of refraction and reflection ; and evidence is also 

 found in that work that he reconstructed the concentric 

 mirrors of Archimedes. In " M. irabili Potestate Artis et 

 Natures" he again treats of refraction of luminous rays, and 

 explains by it the mirage so frequent in the East. In Opus 

 Majus he deals (page 337) with magnifying glasses in a 

 superior manner. After describing concave and convex 

 glasses and the difference of their respective effects, he says : 

 " It is easy to conclude from the laws just spoken of that the 

 largest things may appear small, and vice verscl ; that remote 

 objects may appear quite close, and reciprocally ; for we can 

 cut glasses in such a manner, and adjust them in such a way 

 as regards our eyesight and exterior objects, that the beams 

 * Speculum Alchemiae, Cap. v. 



G fl 



