806 PROFESSOR PIAZZI SMYTH ON COLOUR, 
RED-LILAC GLASS—continued. 










TWO RED-LILAC GLASSES INTERCEPT. 
Intensity, ; Wave-number | Colour Region by 
Max. =10. i in Brit. inch. | Wave-number. 
First black-red light appears at . ; 0-1 25130 | 34 014 | Crimson Red 
First strong red light : : ; 0-7 25°226 | 36 062 | Rep 
Maximum LIGHT : ; : < : 45 25625 | 40 650 | Amber 
Green shade begins . , ; : 5 4-2 25°758 | 42 123 | Amber 
Bright green ends : 2°0 26:040 | 45 208 | Crrron 
Last faint green light, gray Tight afterwards 20 26210 | 46 816 | CrTRON 
Middle of long darkest region . ; : 0:2 26800 | 51 733 | Glaucous 
First bluish violet . 2° 2. 1) “0% 1 27460) 56 657) Blue 
More decided violet . : ; : , 12 27:640 | 58 140 | VioLEr 
Maximum VIOLET . : ; E : 14 27950 | 60 496 | Lavender 
End of all light 4 5 z c . 0:0 28°300 | 63 452 | LAVENDER 



FOUR RED-LILAC GLASSES INTERCEPT. | 




First faint black-red light at . . .| 00 | 25030] 32 468 | Crimson Red 
First decided red light. : 2 : 0-4 25170 | 34 722 | Crimson Rep 
Maximum Licut : : , ; : 03 25:320 | 37 313 | Scarlet | 
Faint dark band . : : é ; 0-6 25°420 | 38 314 | Scarlet 
SECOND MAXIMUM. : : ; : 08 25560 | 40 000 | Amber 
Alllightends . i ; ; ; : 0:0 25°715 | 41 667 | Amber 


Six plates of this glass all but absolutely, and eight plates do absolutely, extinguish every 
trace of the lamp flame. This sort of glass, moreover, is more eminent as a darkener of all the 
spectrum than a transmitter of some portion in particular and a darkener of the rest. If, too, 
it does darken the yellow and green portions chiefly, it does so in a far more smooth and 
equable manner than cobalt-blue glass or blue-lilac glass. Hence Rep-Linac glass promises to 
be useful as sun-shades, and solar spectrum shades. 
RUBY-RED GLASS. 

COAL-GAS FLAME’S CONTINUOUS SPECTRUM (Repgarep). 



Intensity, Wave-number | Colour Region by 
Max. = 10. oe in Brit. inch. | Wave-number. 
False glare from internal reflections . ; 05 24642 | 26 596 | Ultra Red 
True but faint black-red light . ; 0:3 24965 | 30 864 | Crimson Red 
Strong red light, seen at. : ; 3:0 25145 | 34 305 | Crimson Red 
D slit, red side thereof 2 . : ; 9-0 25°823 | AZ 827 "| Amber 
»  yellowside . : 5 ; ; 9°3 25°873 | 43 384 | YELLOW 
Maximum LIGHT : 4 é : 9:5 25940 | 44 053 | YELLow 
Green light ends, blue begins at. , 9-0 26°220 | 46 948 | CrTRoN 
Blue light ends, violet light 1 ee ‘ ; 30 26670 | 58 140 | VioLEr 
All light ends at 3 : : 0:0 28430 | 64 516 | LAVENDER 







