238 WRIGHT—CRYSTALLOGRAPHIC PROPERTIES. [June 1, 
DOMEYKITE. 
Twelve domeykite crystals were measured, all of which indicated 
the holohedral division of the hexagonal system with the following 
observed forms : 
Letter : c b a z v p x 
Symbol Bravais........ QOOI 1010 1170 2023 I011 2021 Ti2Z2 
Goldschmidt.... 0 ome) 00 20 10 20 4 
Also two uncertain forms ? 1 0 (1016), which occurred only once 
6 ’ y 
of the light may be regulated. An ammeter may be used, but is hardly neces- 
sary, In the slits in the tube (/) two small colored (blue and green) pieces of 
glass are placed, which cut down the intensity of the light and impart to it a color 
restful to the eye. In case very bright light is needed one of the glass plates 
Fig. A. 
may be removed. The carbons are observed through a round piece of glass fitted 
in the cap (¢). The electric arc goniometer lamp is especially adapted for the 
measurement of etch figures and minute crystal faces, but serves equally well for 
ordinary measurements as the light intensity may be regulated and cut down at 
will. 
