by doubly refracting crystals. 
List of absorbing Crystals with Two axes. 
19 
Plane of the resultant 
axes in the plane of 
prim, polarisation. 
Plane of the resultant 
perpendicular to the ] 
of prim, polarisation. 
Topaz blue 
White 
Blue 
green 
White 
Green 
greyish blue 
Reddish grey 
Blue 
pink 
Pink 
White 
pink yellow 
Pink 
Yellow 
yellow 
Yellowish white 
Orange 
Sulphate of barytes 
yellowish 
purple 
Lemon yellow 
Purple 
yellow 
Lemon yellow 
Yellowish white 
orange 
yellow 
Gamboge yellow 
Yellowish white 
Kyainte 
White 
Blue 
Dichroite 
Blue 
Yellowish white 
Cymophane 
Yellowish white 
Yellowish 
Epidole olive green 
Brown 
Sap green 
whitish gr. 
Pink white 
Yellowish white 
Mica 
Reddish brown 
Reddish white 
The following table shows the characters of m and n in 
crystals with two axes, which I have not been able to exa- 
mine in every azimuth. 
Axis of prism in the 
plane of primitive 
polarisation. 
Blood red 
Blue 
Greenish white 
Bluish green 
Yellow 
Mica 
Acetate of copper 
Muriate of copper 
Olivine 
Sphene 
Axis of prism perpendicu- 
lar to the plane of primi- 
tive polarisation. 
Pale greenish yellow 
Greenish yellow 
Blue 
Greenish yellow 
Bluish 
* The tints are given in relation to the short diagonal of its rhOmboidal base. 
