GROOVED SURFACES OF METALLIC AND TRANSPARENT BODIES. 305 



Scarlet. 



Purple. 



Third limit of pink and blue . 



Blue. 



48 00 



Brilliant green. 

 Yellowish green. 

 Yellow. 

 Reddish .... 



10 00 



Such being the phenomena exhibited by the ordinary image formed by re- 

 flexion from the original spaces n, I now proceeded to examine the prismatic 

 images in the first specimen with 1000 grooves, and I observed the following 

 appearances. 



Let A B, Fig. 1 , be the reflected image 

 of the rectangular aperture from the spaces 

 n, and a b, a' b', a" b", a'" b'", the prismatic 

 images of it, v v, v' v', &c. being the violet 

 sides, and rr,r'r', &c. the red sides of these 

 spectra. Then in the 



1st spectrum ab, the violet rays are ob- 

 literated at m at an incidence of 74°, and 

 the red rays at n at an incidence of 66°, 

 the intermediate colours, blue green, being 

 obliterated at intermediate points between 

 m and «, and at angles of incidence inter- 

 mediate between 74° and 66°. In the 



2nd spectrum a! b', th,e violet rays are 

 obliterated at m! at an incidence of 66° 20', 

 and the red at n' at 55° 45'. In the 



3rd spectrum a" b", the violet rays are 

 obliterated at m" at 57°, and the red at n" 

 at 41° 35'. And in the 



4th spectrum a'" V", tlie violet rays are 

 obliterated at m'" at 48°, and the red rays at nl" at 23° 30'. 



Another similar succession of obliterated tints takes place on all the pris- 

 matic images at a lesser incidence, as shown at ^v, ^ »', the violet being obli- 

 terated at f/j, and the red at v, and the intermediate colours at intermediate 



MDCCCXXIX. 2 R 



