nDichroscopeAn instrument for examining the dichroism of crystals.
Century Dictionary and Cyclopedia
ndichroscopeAn instrument for testing the dichroism of crystals, usually consisting of an achromatized double-imago prism of Iceland spar, fixed in a brass tube which has a small square hole at one end and a convex lens at the other, of such power as to give a sharp image of the square hole. On looking through the instrument the square hole appears double, the light which passes through being divided into two rays polarized in planes at right angles to each other; and if a dichroic crystal is placed in front of it, the two images, corresponding to the two sets of light-vibrations, will appear of different colors. A dichroscope may be combined with the polarizing apparatus of a microscope.
Chambers's Twentieth Century Dictionary
nDichroscopean instrument for testing the dichroism of crystals
Webster's Revised Unabridged Dictionary
Gr. di- = di`s- twice + color + to view
The use of a dichroscope would have saved them that error, for the stone is singly refracting.
"A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public" by Frank Bertram Wade