Chap, i.] [ 155 3 



BOOK III, 



CHAP. I. 



HISTORY OF DISCOVERIES CONCERNING 

 LIGHT, &c*. 



Opinions of the Platonics. -Of Arijiotle. Of Alhazen. Of Roger 

 Bacon. The Invention of Spectacles. Treatife ofMaurolycus on Vi- 

 Jton.Long and /hort Vijion. Reafon that the Sun's Image appears 

 round, though the Rays pafs through an angular Aperture. In<ven- 



- tion of the Camera Obfcura. Conjectures of Fletcher on the Rain- 

 borvu. Invention of the Telefcope Suppofed to be by Zacharias 

 Janfcn. Galileo. Kepler.' Invention of the Micrcfcope.'Tycho 

 Brake. Reformation cf diftorted Images.'-* Snellius and Hortenjiuf. 

 Defcartes, Scheiner. Velocity cf Light difcovered. Boyle's 

 Difcci>eries en Colours. Grimaldi. Gregory. Newton ; his Dif- 

 coveries on Cohan. On Refrangibility. Bolognian Stone. Bald- 

 nuin's Phojphgrus, &c. -Bradley.- Bouguer. Melville.^ T)ollanJ, 

 De la Motte.Dela<val. 



H E mod ancient hypothefis, which leads to the 

 JL true theory of light and colours, is that of the 

 Platonics, namely, that light, from whatever it pro- 

 ceeds, is propagated in right lines ; and that when it 

 is reflected from the furfaces of polifhed bodies, the 

 angle of reflexion is equal to the angle of incidence. 



To 



* The unfcientinc reader is earneftly requefted to give parti- 

 cular attention to the following fhort axioms and definitions, 

 which will enable him not only better to underftand this chapter* 

 but all the fuccecding ; and if in the coiufe of this book any diffi- 

 culty 



