IN PRACTICAL ASTRONOMY, SPECTROSCOPICALLY EXAMINED. 
BLUE-LILAC GLASS 

continued. 
813 


TWO BLUE-LILAC GLASSES INTERCEPT. 

Intensity, 
Max. =10. 

First black-red light . 
Strong red light 
Full red light 
Maximum Rep LIGHT 
Middle of dark band 
Maximum of ORANGE LIGHT 
Middle of a dark band 
Chief Maximum G'reen-yellow 
Green edge of a very broad darkish band 
Middle of said dark broad band 
Violet edge of said dark band 
Maximum of VIOLET LIGHT 
End of all light 


Wave-number 
in Brit. inch. 
Colour Region by 
Wave-number. 

0-1 
kal 
2°0 
3:3 
31 
39 
J3 
56 
33 
1:0 
vs 
2:3 

0-0 

24960 
25°100 
25°180 
25°330 
25°475 
25°670 
25°880 
26:060 
26°180 
26°820 
2'7°220 
27-910 
28°370 

FOUR BLUE-LILAC 
Light begins at 
Maximum Red light 
Middle of dark band . 
Maximum Orange light 
Middle of dark band . 
Maximum Green light 
Beginning of dark broad band 
End of light. ‘ i F 
Light begins again, violet in colour 
Maximum VIOLET Licut 
End of all light 

GLASSES INTERCEPT. 
0:0 
26 
er 
27 
16 
2-9 
0°6 
0:0 
Oa 
13 
0:0 


24:975 
25260 
25°480 
25660 
25°8350 
26015 
26°180 
26°400 
27°580 
28:060 
28°230 

31 
33 
34 
37 
39 
41 
43 
45 
46 
51 
54 
60 
64 
447 
557 
904 
313 
170 
186 
535 
393 
555 
840 
765 
168 
144 

Crimson RED 
Crimson RED 
Crimson RED 
SCARLET 
ORANGE 
AMBER 
YELLOW 
CITRON 
CITRON 
GLAUCOUS 
GLAUCOUS 
LAVENDER 
LAVENDER 


ol 
36 
39 
41 
42 
44 
46 
48 
57 
61 
62 
646 
311 
262 
085 
918 
984. 
555 
497 
637 
387 
854 

Crimson RED 
RED 
ORANGE 
AMBER 
AMBER 
YELLOW 
CITRON 
GREEN 
INDIGO 
LAVENDER 
LAVENDER 



Eight blue-lilac glasses show a mere ghost of a red band, with maximum in 34 360 
Wave-number. 
QUALITIES OF SIMPLE GLASSES. 
From the above notes we may deduce for each kind of glass tried, as follows :— 
Rep-Li1ac, is a general broad obscurer ; though obscuring most over the green and blue 
next the yellow and violet ; leaving the red near C, slightly in favour. 
Wherefore this glass may be useful in dulling sun-light in the middle of the spectrum, and 
promoting examination of all the red region of tt. 
BivE-LILAc, obscures broadly the green and blue, and admits broadly, though faintly, the 
violet, but tends to produce narrow bands in the red and yellow. In greater thicknesses it 
admits a faint band of red near little a (Solar), and a faint, broadish band of violet between G 
and H ; in fact, farther towards the violet end than any other known glass. 
Therefore this colour may be switable for observations at the violet end of the spectrum. 
VOL. XXVIII. PART III. 
10 D 
