IN PRACTICAL ASTRONOMY, SPECTROSCOPICALLY EXAMINED. 799 
same colour, viz., green ; but on converting my eye into the di-chroic kind by 
holding the blue-green black bottle before it, behold I see the two objects as 
different as possible from each other in colour, one being green and the other 
red. 
Hence this reputed law requires decided correction or limitation ; for an 
artificially di-chroicised eye certainly, and for many a naturally di-chroicised One 
probably: while experiment on the latter class, might well repay some advanced 
physiologist to institute; especially if he should make it on so extensive a 
scale as to eliminate accidents and varieties of human eyes, as to their internal 
coloured humours, whose tints, dear to the poet and the lover, are legion. 
Meanwhile, however, in certain cases, depending more on physics than optics, a 
di-chroicised natural eye (as in the above grass and venetian blind case) may 
perceive not a less, but a greater, variation of tints than a tri-chroic eye; and 
therefore has a sensible advantage in some exact questions. 
“ But,” asks an esthetic friend, “though it may be useful occasionally in 
mere mechanical science,—can it ever be desirable in the beautiful, the exalted 
Fine-Arts to see anything with an eye that makes green grass red ?” 
Yes itis! Especially when you find that such an eye has a whole gamut 
of choice and various reds. So that if it preserves some of its richest red for a 
carpet of standard green grass, it has orange red for yellow green; lakey red 
for blue-green; and purple red, madder-brown red, and bronzed red for 
the duller greens of diverse plants at sundry seasons of the year. While many 
of the most exquisite dove-coloured, and other balancing tints, are either left 
untouched, or so decidedly re-inforced, as to make a more effective picture for 
light and shade on the whole, than the ordinary view. Contemplate the cases 
however carefully, practically, both by anxiously painting them out from 
Nature* and also by reading up Art-authors,—and you may presently be gifted 
to see, that the new Di-chroic spectroscopy has at last most effectively solved 
for man, that ultra difficult Art-problem which has puzzled Tri-chroic-eyed 
painters for centuries; viz., how to dispose of, or allowably substitute, with 
pictorial mellowness, “that crude colour green.” 
The best Dutch and Flemish landscape painters, strivimg in their day after 
noble ideals, rather than mere realistic transcripts, eschewed green altogether ; 
and employed, as their method of solving the problem (so far as they then 
dared), “warm brown” instead; aiming always for a grass lawn at the ex- 
quisitely melodious tint, the glorious colour, of “an old Cremona violin” ; and 
* J made several coloured sketches this last summer in Lisbon, first as seen direct or simply by my 
natural tri-chroic eye, and then as seen by looking through the dark-green di-chroic bottle : and if the 
trees at an old mill door, did stand up in this latter case like gigantic red corals, there were magnificent 
shades of dove-coloured gray behind, and pale sea-green sky above them to satisfy the most fastidious 
eye as to abstract theory, and splendour of effect, though not as to ordinary terrestrial experience. 
VOL. XXVIII. PART III. 9 Z 
