36 ESSAYS anp OBSERVATIONS 
a livid yellowifh caft: And yellow alone 
appears unaltered and extremely lumi- 
nous. Thefe experiments I made with dif- 
ferent forts of rich-coloured bodies, as 
filks, cloths, and paints. Polifhed copper, 
which has contracted from the air a high 
flaming colour, is reduced by the fame 
light into the appearance of yellow brafs ; 
the faces and hands of fpectators appear 
like thofe of a dead corpfe; and other 
mixed colours, which have red or green 
in their compofition, undergo like chan- 
ges. 
27. Havine placed a pafte-board with 
a circular hole in it between my eye and 
the flame of the fpirits, in order to dimi- 
nifh and circum{cribe my object, I exami- 
ned the conftitution of thefe different 
lights with a prifm, (holding the refract- 
ing angle upwards) and found, that, in 
the firft cafe [N° 25.], when fal ammon. 
alum, or potafh fell into the fpirits, all 
forts of rays were emitted, but not in e- 
qual quantities; the yellow being vaftly 
more copious than all the reft put toge- 
ther, 
