| 
| [gge d when either of the axes are incline 
O. N. Rood on Circular Polarization, 393 
From these observations it will be seen that the crosses remain 
waltered when viewed through the centres of regular polygons, 
as for example, the square, the octagon, and the circle, the latter 
ing considered a regular polygon with an infinite number of 
sides; the centres of such polygons are therefore uniaxial and cor- 
: respond to the basal plane of uniaxial crystals: the positions of 
these solids which I have marked 0 correspond with the pris- 
mane faces of uniaxial crystals; the portions marked with num- 
bers correspond in a certain sense with the planes of the quad- 
tatic pyramid. It is remarkable that we should have in portions 
of om plate a representation of the action of all the planes of a 
crysta 
The central portions of the ellipse and rectangle correspond 
to the basal plane of a crystal belonging to the rhombic system ; 
the rhombic plate of glass had not been cooled with sufficient 
regularity to base a conclusion on its action though indications 
- Were observed which would place it along with the ellipse—at 
all events the spots marked s acted like the rhombic shaped ba- 
= of a rhombic prism. 
¢ centre of the triangle corresponds in action to a plane of 
the quadratic pyramid. , 
2. Observations on Circular Polarization by means of Cooled Glasses. 
light by transmission through the corners of the square plate ; 
ta “eign as an easy method of producing circularly po- 
t. 
larized 
Thave found that when a beam of awe mere (see 
Apes eee ee 
jbonds to that of Dove’s cube. The polarization was right-— 
tion | e., to the plane of primitive polarization. The polariza- 
a / 
