OPTICS. 353 



assigned by biblical critics to Moses as the author, we have (xxxvii. 18) 

 in the address of Elihu to his afflicted friend, the inquiry : 



" Hast thou with him [God] spread out the heavens, 

 Polished as a molten-mirror?" 



Pliny assures us 1 that the pagan women, when attending the worship 

 of their deities, were ornamented with metallic mirrors ; and it seems 

 extremely probable, as Cyril, of Alexandria, has affirmed, 2 that the 

 Israelitish women borrowed this custom from the Egyptians, and 

 attempted to introduce it into their own worship. These early mirrors 

 were flat, and so they appear to have been, generally, down to the time 

 of Prasitelis, who lived in the reign of Pompey the Great. 



His mirrors chiefly consisted of hammered plates of pure silver, as Prasiteiis's 

 we learn from the words of Pliny : " Lamina duci et specula fieri mi " c j s ' 60 

 non nisi ex optimo (argento) posse creditum fuerat." But the silver 

 was sometimes mixed with other metals : " Id quaque jam fraude 

 corrumpitur." Pliny further informs us, that " Specula quoque ex eo 

 (stanno) laudatissima, Brandusii temperabuntur, donee argenteis uti 

 caspere et ancillse." Highly-praised mirrors were manufactured at 

 Brundusium, till the very maid-servants began to use silver ones. The 

 monster, Nero, who it seems was short-sighted, employed as a mirror 

 an emerald, reduced to a polished surface, on which he viewed by re- 

 flection, the combats of the gladiators. Here, however, is no optical 

 science. 



Aristotle is the earliest author whose writings on the subject of Aristotle, 

 optics have reached our times; but, unfortunately, he has not been B>c - 350 ' 

 more successful in this branch of research than he was in reference to 

 mechanics. His speculations on the nature of the rainbow, on the 

 manner in which we perceive objects, and on different optical pheno- 

 mena, are not merely crude, but generally erroneous; and in his 

 treatise, Hepl Xpo/zarw*', ' De Coloribus,' everything is so vague and 

 foreign from correctness of explication, that we should not hold our- 

 selves justified in presenting any detail. 



Soon after Aristotle, the celebrated geometer Euclid composed a Euclid, 

 book on this subject. It appears under the title, 'OTTTIKO. (neuter plural),. B * c> 300 ' 

 and has been sometimes ascribed to another author bearing the same 

 name. , We are of opinion, however, that it fairly belongs to the 

 geometrician, and that it is the ' Introduction' only which was written 

 by another hand. As the deductions of Euclid, though founded upon 

 a wrong hypothesis, are curious, considering the state of mixed mathe- 

 matics at the epoch in which they appeared, we shall present a 

 synopsis of them in this place. 



Light propagates itself in right lines, as is shown by the shadows of Propositions, 

 bodies, and by the passage of light through a door or window. 



If the luminous object be equal to the object illuminated, the sections 



1 Lib. xxxiii. c. 9 ; lib. xxxiv. c. 17. 



2 Lib. ii. De Adoratione in Spiritu. 



[G. E. P.] 2 A 



