786 
PROFESSOR PIAZZI SMYTH ON COLOUR, 
Tea-infusion. 
Sulphate of Copper. 
Green glass, stained green. 
DI-CHROICS. 
Permanganate of Potassium. 
Oxalate of Chromium and Potash. 
Cobalt-blue glass. 
Litmus solution. 
Judson’s Peach-blossom dye. 
Cambridge blue. 
——— Oxford blue. 
—-~-—- Violet. 
Purple. 
— Mauve. 
Green. 
Green heavy flint glass, innately green from lead. 



POLY-CHROICS. 
Red-lilac glass. 
Blue-lilac glass. 
Judson’s Lavender dye. 
Plum-colour. 
and perhaps Didymium Nitrate. 

As the Di-chroic colours will chiefly occupy us in what is to come, we may 
as well tabulate here a further variety amongst them; viz., the tendency of 
some to become more red, and others blue, with increased thicknesses ; or 
thus :-— 
RED-WARD Di-chroics. 
Oxalate of Chrom. and Potass. slatey-blue. 
Litmus blue. 
Judson’s Green. 
—W Peach-blossom pink. 
——-— Violet. 
Purple. 
——— Ruby, and 
——— Mauve. 
4 

BLUE-WARD Di-chroics. 
Permanganate of Potassium pink. 
Cobalt-blue glass. 
Judson’s Cambridge blue. 
. -_— Oxford blue. 
