On Dimorphism of Arsenic, Antimony and Zinc. 198 
s 
In another ydrogen gas was reduced 
2 © ee a | h 
in a bohemian glass combustion tube in the usual way, when 
tube having two branches each provided with a stop-cock with 
a hydrogen generator on the one hand and on the other with a 
gas bottle generating arseniuretted hydrogen. The last was 
provided with a safety tube by which the excess of gas not 
needed in the experiment might escape. Before heating the 
combustion tube it was filled with hydrogen from the generator by 
which a uniform current of gas through the tube was maintained 
during the process. A portion of the tube two or three inches 
long was next heated to a red heat and then by opening the 
stop-cock a very small amount of arseniuretted hydrogen was al- 
lowed to mix with the hydrogen current and the experiment con- 
tinued until a metallic mirror was formed on the glass beyond the 
heated portion of thetube. This mirror examined by the micro- 
Scope, was found to be studded with minute octahedral crystals, 
which were submitted to the same test as before and with the 
same results. 
vations were made on the ordinary regulus of antimony, which 
1s now known to have ccavaenal cleavages. After crystal- 
lizing arsenic in octahedron by the process last described the 
author succeeded in obtaining octahedral crystals of antimony 
with the same apparatus, using antimonuretted hydrogen in 
Se of arseniuretted hydrogen. The tube was heated with & 
and presented the same characteristic forms. T id angles 
of the octahedrons were very frequently observed modified 
the faces of the cube and in ‘one the edges were 
fications are of importance as ey remove all doubt in regard 
to the system of crystallization. The crystals being microscopic 
their interfacial angles could not of course be measured, but the 
