Sentence Examples with the word Black Cross

Then with an uniaxal plate perpendicular to the optic axis, the black cross is replaced by two lines, on crossing which the rings are discontinuous, expansion or contraction occurring in the quadrants that contain the axis of the quarter-wave plate, according as the crystal is positive or negative.

Such a section when examined in the polariscope shows an interference figure with a coloured centre, there being no black cross inside the innermost ring (this is not shown in very thin sections).

The Order of the Iron Cross, the badge of which is a black cross with gold borders, with a gold centre bearing a lion, was instituted by Leopold II.