154 THe Microscope. 
A PECULIAR DUST IN SNOW. 
ie February, 1884, a peculiar sediment was accidentally dis- 
covered in snow water at St. Joseph, Mo. Dr. H. Christo- 
pher needing some pure water for chemical purposes, melted 
some apparently clean snow, and called my attention to the 
above-mentioned deposit. Afterwards a fine, feathery snow 
fell upon a coating of sleet and ice,which covered the surround- 
ing country for hundreds of miles. Upon melting this surface 
snow, the water was found to contain the same unusual sedi- 
ment. As the entire adjacent country, and the sand bars of the 
Missouri river, were covered with ice, it seemed remarkable to 
find this substance in snow falling upon it. Accordingly this 
dust was treated with chloro-hydric acid, and heated on plati- 
num foil at a red heat to eliminate any carbon or accidental or- 
ganic matter. Upon washing it in a test tube, it was found to 
be so minute that portions of it required hours to settle to the 
bottom. Thinking it might possibly be of local origin, samples 
were gathered from different parts of the city, and from the 
country far from habitations. Some were treated as above, 
and some simply dried. 
Its behavior under chemical examination convinced us of 
its silicious nature. It was then submitted to microscopical ex- 
amination and found to consist of flat plates and sharp angled 
fragments, transparent vitreous pieces, some brownish semi- 
transparent particles, jet black sharp-pointed pieces, and needle- 
like spicules. However, every piece fragment or minute nee- 
dle, showed a clean-cut, sharply defined margin, and no rounded 
masses with worn sides were found. After a careful examina- 
tion it was considered volcanic dust. It was compared with 
sand from Coney Island, Lake Erie, the Mammoth Cave, and 
the Missouri River. These various sands were much coarser, 
appearing as rounded masses, destitute of the clean-cut edges 
of the snow sand. So great was the difference no one could 
confound the two. In order to guard against self-deception, 
thinking it might be ashes from anthracite fires, or dust from 
foundries and blast furnaces, they were obtained and found to 
present an altogether different appearance. 
