r\FrJTRN<^K r,V 'J'HK ItoM.W EMPfKK. 183 



inferior to the philosophically combining Theophrastes, while 

 the delicacy of his manner of dissecting, and the extent of his 

 physiological discoveries, place Galen, who extended his ob- 

 servations to various genera of animals, " very nearly as high 

 as Aristotle, and, in some respects, even above him." This 

 judgment embodies the views of Cuvier.* 



Besides Dioscorides and Galen, our attention is called to a 

 third and great name — that of Ptolemy. I do not mention 

 him here as an astronomical systematizer or as a geographer, 

 but as an experimental physicist, who measured refraction, 

 and who may, therefore, be regarded as the founder of an im- 

 portant branch of optical science, although his incontestable 

 claim to this title has been but recently admitted.! How- 

 ever important were the advances made in the sphere of or- 

 ganic life and in the general views of comparative zootomy, 

 our attention is yet more forcibly arrested by those physical 

 experiments on the passage of a ray of light, which, preceding 

 the period of the Arabs by an interval of five hundred years, 

 mark the first step in a newly-opened course, and the earliest 

 indication of a striving toward the establishment of mathe- 

 matical physics. 



The distinguished men whom we have already named as 

 shedding a scientific luster on the age of the imperial rulers 

 of Rome were all of Greek origin. The profound arithmeti- 

 cian and algebraist Diophantus (who was still unacquainted 

 with the use of symbols) belonged to a later period.:}: Amid 

 the difierent directions presented by intellectual cultivation in 

 the Roman empire, the palm of superiority remained with the 

 Hellenic races, as the older and more happily-organized peo- 



* Cuvier, Hist, des Sciences Naturetles, t. i., p. 312-328. 



t Liber Ptholemei de Opticis sive Aspectihis ; a rare manuscript of the 

 Royal Library at Paris (No. 7310), which I examined on the occasion of 

 discovering a remarkable passage on the refraction of rays in Sextus Em- 

 piricus {adversus Astrologos, lib. v., p. 351, Fabr.). The extracts which 

 I made from the Paris manuscript in 1811 (therefore before Delambre 

 and Venturi) will be found in the introduction to my Recueil d* Obser- 

 vations Astronomiques, t. i., p. Ixv.-lxx. The Greek original has not been 

 preserved to us, and we have only a Latin translation of two Arabic 

 manuscripts of Ptolemy's Optics. The name of the Latin translator 

 was Amiracus Eugenins, Siculus. Compare Venturi, Comment, scpra la 

 Storia e le Teorie delV Ottica, Bologna, 1814, p. 227 ; Delambre, Hist, 

 de V Astronomic Ancienne, 1817, t. i., p. 61, and t. ii., p. 410-432. 



t Letronne shows, from the occurrence of the fanatical murder of 

 the daughter of Theon of Alexandria, that the much-contested epoch of 

 Diophantus can not be placed later than the year 389 (Sur V Orisrinf 

 Qrecqiie des Zodiaqi/es prefendns Egyptiens, 1837, p. 26). 



