362 



GREEK SCIENCE. 



three equidistant " sights," as they are technically called. A figure of 

 it is given in M. Halma's edition of the ' Almagest.' 



From what has been stated, then, it will be seen that the ancients 

 had but little that deserved the name of optical science ; that what 

 they possessed was confined almost entirely to catoptrics, and was, 

 even in reference to that department, extremely imperfect ; that their 

 instruments were chiefly catoptrical, some of which, however, they 

 carried to very high perfection ; and that we have no proof that their 

 dioptric instruments went beyond single lenses, prisms, and multiply- 

 ing glasses. In reference to refraction, the few researches which they 

 had instituted, seem to have been ingenious and partially successful. 



Thales. 

 B. c. 600. 



Theophras- 

 tus. 



B.C. 321. 



Pliny. 



A. C. 70. 



Solinus. 

 A.C. 218. 



VI. ELECTRICITY. 



In attempting to give a short abstract of the history of that branch 

 of Physics now universally termed Electricity, it will be perceived 

 that a single fact observed in the earliest ages, and as far as our in- 

 formation can reach, at first recorded by the Greek philosophers, has 

 by the subsequent addition of analogous phenomena, created and given 

 name to a separate and important science. 



Thales of Miletus, who flourished about 600 years before the 

 Christian era, is reported by subsequent writers to have described the 

 power developed in amber by friction, by which it was enabled to at- 

 tract bits of straw, and other light bodies ; and an attempted expla- 

 nation of this phenomenon is given as one of his philosophical dogmas. 

 In the treatise of Theophrastus upon stones, we have the earliest de- 

 scription extant of this property, " eirel Se KCU TO rjktKTpov XiOog, Kal 

 yap opvKTOv TO Trtpl AtyvffTiKijv Kal TOVTMV av r; TOV e\Keiv ^vvafjug 

 aKoXovddrj" (Theoph. ' de Lapid.' p. 134, Hill's edit.) Speaking 

 also of the ' Lyncurium,' he says, " 2Xm yap dffirep TO ijXeKTpov 61 

 3e tyaaiv 6v povov Kapfyr) Kal uAov, dXXa Kal ^a\Kor Kal crifirjpov, iav 

 TI XtTrroc <u(77rep Kal Aic/cX^e f'Xtyev." (p. 124.) 



It does not appear that Pliny's knowledge upon this subject ex- 

 tended beyond that of Theophrastus : he states of pieces of amber 

 that " attritu digitorum accept^, vi caloris attrahunt in se paleas et 

 folia arida, ut magnes lapis ferrum " (Plin. lib. xxxvii. cap. iii.) ; and 

 " nee folia autem aut stramenta in se rapere, sed seris aut ferri laminas." 

 Like Theophrastus, he also mentions the lapis Lyncurius as possessed 

 of the same property. In the same chapter he adds, " In Syria 

 quoque foeminas verticillos inde facere et vocare harpaga, quia folia, et 

 paleas, vestium fimbreas ad se rapiat." Similar quotations might 

 easily be adduced from the writings of Priscian and Solinus. Salma- 

 sius, in his commentary upon the latter author, asserts that karabe, the 

 word by which amber was known among the Arabs, is said by Avi- 

 cenna to be of Persian origin, and to signify the power of attracting 

 straws. (' Hyl. lat.') 



