IN PRACTICAL ASTRONOMY, SPECTROSCOPICALLY EXAMINED. 83 
2. Judson’s GREEN—continued. 
After this, tried 1 to 4 of the usual green (yellow-green) glasses, but found them without 
any trace of a separate red band. Next tried Sol.=10, in bottle on landscape, and, lo! the 
grass-greens were red; as red, or brighter red, than any of the red bricks and tiles near at hand ! 
Stone colour and road colour remained much as before, Venetian shutters, painted green, were 
nearly black. The vermilion of grass came out best when Sun shone on it, and showed it, to 
the naked eye, most green and most distinct from red tile and red brick. Here seems at once 
a short cut to colour blindness; viz., an eye lens or fluid as di-chroic as this blue-green ! 
DIVISION IV.—BLUE MEDIA: 
1, COPPER AMMONTA-CHLORIDE, Water Solution. 
1 1 I 1 1 Eig deel pad 
Solution tried 335, do, go Fo Bo» and 7p. 

Solutions of below the strength of ~,, become milky, and may have to stand for a day or 
two to let some gray matter subside; that done, and the colours being noted by eye, by day- 
light transmitted through 1 inch thickness, 335 has only the faintest tinge of blue; 74,=light 
blue, #5 = blue, {45 = intense blue, ,4; = slightly violet blue; and 5 = also slightly violet 
blue. 

COAL-GAS LUMINOUS FLAME, as foundation. 



Intensity. | fin Brit Inch | Wavoneubon 
First red glare. : : , . : mo 24 86 29 087 | Ultra Rep 
First true red light . : : ; ih 25°18 33 102 | Crimson RED 
Slit, by sodium light, Ist side ; : 11 26°01 43 015 | Yellow 
x a 2dside , ? : TT 26°03 43 203 | Yellow 
Maximum Licut, YELLow . : 3 : 12 26:03 43 403 | YELLOW 
End of all light at violet . : : : 0 28°46 62 712 | Lavender 



Solution 33,5. Though the colour is of the Faanbest, it has a most remarkable effect in 
dulling the over-light yellow region of the spectrum; and doing it oy and 
smoothly, without any of the bands which cobalt-blue glass has. 



25°26 34 095 | Crimson RED 
25°36 35 436 | RED 
26:33 46 382 | CirRon 
26:90 51 653 | GLAUCOUS 
a leas; 58 173 | VIOLET 
28°42 62 500 | LAVENDER 
| First faint beginning , A h 
| Decided light ‘ C ‘ d 
Maximum Licut (in Green) ‘ ‘ 
| Green ends, blue begins 
Blue ends, violet begins 
Endall.. : ‘ 

onwnn NAN FO 


