THEORY OF 



LIGHT 



AND COLOURS. 



169 



Table of colori- 

 fic undulatiout 

 of the ether. 



Scholiwn. It was not till I had fatisfied myfelf reflecting Quotation from 

 all thei'e phenomena, that I found in Hooke's Micrographia, Robert Hooke 



r » exhibiting a fi- 



a paflage which might have led me earlier to a fimilar conclu- m ij ar doctrine, 

 lion. ff It is moll evident that the reflection from the under 

 or further fide of the body, is the principal caufe of the pro- 

 duction of thefe colours. — Let the ray fail obliquely on the 

 thin plate, part therefore is reflected back by the firft fuperfi- 

 cies, — part refracted to the iecond furface, — whence it is re- 

 flected and refracted again. — So that, after two refractions and 

 one reflection, there is propagated a kind of fainter ray—/' 

 and, '*. by reafonof the time fpent in palling and repafling, — - 

 this fainter pulfe comes behind the" former reflected " pulfe ; 

 fo that hereby , (the furfaces being fo near together that the 

 eye cannot difcriminate them from one,) this confufed or du- 

 plicated pulfe, whofe ftrongeft part precedes, and whofe 

 weake ft follows, does produce on the retina, the fenfation of a 

 yellow. If thele furfaces are further removed afunder, the 

 weaker pulfe may become coincident with the" reflection of 

 the fecond," or next following pulfe, from the firft furface, 

 " and lagg behind that alfo, and be coincident with the third, 

 fourth, fifth, fixth, feventh, or eighth — ; fo that, if there be 

 a thin tranfparent body, that from the greateft thinnefs requU 



fite, 



