CRYSTAL PHONOPTICON 
317 
THE CRYSTAL PHONOPTICON IN ITS ADAPTATION TO 
ENABLE THE BLIND TO READ THE 
PRINTED PACE. 
F. C. BROWN. 
The crystal phonopticon is an arrangement of apparatus where- 
by illumination characteristics (e.g. such as come from a small 
portion of any printed page) of variable arrangement, intensity 
and sequence may be transformed into sound progressions of 
corresponding variable intensity, arrangement, duration and 
sequence. It is called the Crystal Phonopticon because by the use 
of recently discovered crystals of selenium^ light impressions 
are transformed into sound impressions,. The key to the suc- 
cessful production of such an apparatus lay in the high sensi- 
Pig. 20. — Diagrams showing characters of selenium crystals. 
bility of these isolated crystals to light. The sensibility is in- 
creased by the transmission of the light action along the crystaP 
much in the same way perhaps that a nervous impulse Is trans- 
mitted along a nerve, and yet further increased by mounting 
the crystal under pressure.^ The increased sensibility of a single 
crystal or a. small group of crystals has made possible the con- 
struction of a far more sensitive apparatus than was possible 
with the old selenium cells as suggested by Fournier D’Albe.^ 
It is not possible to use a selenium cell in the same way that I 
have used individual crystals, of selenium. 
The Selenmm Eye . — The essential part of the crystal phon- 
opticon is the selenium eye, which consists essentially of a row of 
. iPhys. Rev. N. S. 4, p. 85, 1914. 
2Brown and Sieg, Phil. Mag. S. 6, 28, p. 497. 
•*Loc. cit. 
^Proc. Roy. Soc. A, Vol, 90, p. 373, 1914. . 
