212 A. W. Wright—Gases in Smoky Quartz. 
he rock when broken or crushed with a hammer exhales a 
fugitive but unmistakable odor of hydrogen sulphide, but the 
proportion of the gas was too small to be directly detected 
with the ordinary lead-paper even when directly applied as a 
cover to a diamond mortar in which a considerable quantity of 
the material had been powdered. But when a slip © the 
paper was introduced into a tube filled with the extracted 
gases, a slight but distinct coloration was produced. b 
same was true in a somewhat more marked degree with a paper 
moistened with mercurous nitrate, indicating sulphurons oxide. 
ence of sufficient water to moisten the paper slightly. The 
first underwent a slight discoloration, which after a time dis 
appeared, the second assumed a pinkish tint, while the thi 
was distinctly blackened, thus proving the presence of a trace 
of both the gases in question, a conclusion moreover which 
was verified by other and independent trials. 
As both hydrogen sulphide and sulphurous oxide are ab- 
sorbed by potassic hydrate it was important to ascertain 
gases were not present in any measurable quantity. 
oO 
out. 1e temperature of the freezing mixture was from eed 
to —20° C., so that the tension of the residual vapor was gir 
than one millimeter, which was confirmed by the reading © 
