20 THE MICROSCOPE. Feb. 
We have found that a low temperature favors the for- 
mation of tubular crystals: a higher temperature the star- 
shaped crystals; but these groups show such different 
forms that it is necessary to seek other causes. Here is 
a broad field for investigation and study. 
Silicon Dioxide. 
By W. S. BEEKMAN. 
WEST MEDFORD, MASS. 
Among the grandest developments of a most subtle 
molecular aggregation, nothing issues from the Labora- 
tory of the Unseen Architect, possessing more interest- 
ing features, than Silicon Dioxide. 
An invisible gas, and‘a silvery metallic looking sub- 
stance. We must suppose, the mystic interposition of a 
Titian Alcahest, and then these two most peculiar sub- 
stances, amalgamate. 
Among the most intense degrees of exquisite gem lim- 
pidity; among the most gigantic examples of mathemat- 
ical refinement; among the most gorgeous displays of 
light interference; this blending of two such strange 
characters excels. 
Have you ever feasted upon the extreme magnificence 
presented by the combinations of crystal splendor, for 
which, from among all other things, quartz seems to be 
the most plentiful example. 
As among people, so among Rock Blossoms, are the 
peculiarities induced by each different locality. So faith- 
fully is it wronght into its substance, that a collector needs 
but see a specimen to almost locate it. 
The limpidity of Japanese quartz; the transparency of 
of the highest refinements of North Carolina quartz are one 
and the same thing; yet one soon detects which is which. 
The crystals from Hartz Mountains; and the crystals 
from Pike’s Peak ; they may be both pellncid solidifica- 
