334 Dr. Darwin’s Experiments on the 
fpedlrum was yellow, being the reverfe fpedlrum of the violet 
paper, and the external one was violet, beingthediredlfpec- 
trum of the violet paper. 
c. When fix inches fquare of pink paper was viewed on a foot 
fquare of blue paper, the internal fpedlrum was blue, and the 
external fpedlrum was pink ; that is, the internal one was the 
diredl fpedlrum of the external objedl, and the external one was 
the diredl fpedlrum of the internal objedl, inftead of their being 
each the reverfe fpedlrum of the objedls they belonged to. 
, d . When fix inches fquare of blue paper were viewed on a 
foot fquare of yellow paper, the interior fpedlrum became a 
briiliant yellow, and the exterior one a brilliant blue. The 
vivacity of the fpedtra was owing to their being excited both by 
the ftimulus of the interior and exterior objedls ; fo that the 
interior yellow fpedlrum was both the reverfe fpedlrum of the 
blue paper, and the diredl one of the yellow paper; and the 
exterior blue fpedlrum was both the reverfe fpedlrum of the 
yellow paper, and the diredf one of the blue paper. 
e . When the internal area was only a fquare half-inch of 
red paper, laid on a fquare foot of dark violet paper, the in- 
ternal fpedlrum was green, with a reddifh-blue halo. When 
the red internal paper was two inches fquare, the internal 
fpedlrum was a deeper green, and the external one redder. 
When the internal paper was fix inches fquare, the fpedlrum 
of it became blue, and the fpedlrum of the external paper was 
red. 
f When a fquare half* inch of blue paper was laid on a fix- 
inch fquare of yellow paper, the fpedlrum of the central papef 
in the clofed eye was yellow, incircled with a blue halo. On 
looking long on the meridian fun , the difc fades into a pale blue 
furrourided with a whitilh halo. 
c Thefe 
f 
