The morning call. [volume] (San Francisco [Calif.]) 1878-1895, 1890-12-14
CHANGEABLE STONES.
Peculiar Actions of Paradoxical
Pebbles in the British Museum.

Among the thousands Of wonderful things
in the British Museum none is more deserv-
ing OF description than the three little
pebbles known to the geologist of that in
stitution as the 'changeable stones" The
largest of the three is about the size of
cherry stone and CT the same form, perhaps
little more ovate. Living in sthe little
glass case 1t appears to be perfectly opaque
and Of a yellowish color. Paradoxical as it
may seem, it will scratch glass if it is drawn
across it. but can itself be scratched with
common penknife. The various acids have
no effect whatever upon it, but strange to
relate, placed in water it soon becomes per-
1ectly transparent and of a beautiful amber
color.
The change begins almost Immediately
after the immersion at one end of the ovate
in the form of a minute shot or bead, being
In this way wholly unlike the two smaller
"changeable stones" in which the transpar-
ency begins around the edges and grad
ually envelopes the entire stone. In the
large one the little globe-lke spot increases
by degrees until the stone becomes uni
iorInly clear throughout. When removed
from the water the end first to become
transparent is the first to become opaque,
the dark colored globe gradually hiding the
transparency of the whole stone.
Bergman, Veltheim, Magellen and Buck
man, Voinmlnous writers upon the hydro
phanes and other changeable stones, tell us
that some Of the steatites exhibit changes
quite as astonishing as those shown by
the three pebbles in England's great
national curiosity shop. Buchanan and
Veltheim were the first to particularly in
qulre into the nature of steatite and stones
OF similar composition. Their report on
the remarkable changes wrought upon a
piece of steatite upon which they were ex-
perimenting may not be wholly uninterest-
ing 10 readers who have taste for the curl
GUS in its manifold forms.
Ii Is as follows: las soon as the stone
was placed in the water we noted peculiar
musty smell, also that several air-bUbbles
rose to the surface of the water. Soon the
hrst stone showed signs of becoming trans
parent, then several others were dropped
into the same vessel Some of them became
colorless as soon as they were thoroughly
dampened; others took on more or less deep
yellow color; some acquired beautiful ruby
hue, and others still the color of mother-Of-
pearl or OF blush opal. Whatever be the
color OF the liquid in which the hydrophane
Is Immersed, it gains only its usual degree
OF transparency. with the color peculiar to
1t. When we look at it in its moist state we
perceive luminous point, varying in its sit
uation as the position of the eye is altered"
The anclents also noticed the peculiar
little luminous spots in the Steatites and
other hydrophanes. which was the cause of
their calling such stones Oculus Mundi
they thinking the spot the image of the sun.
According to Buchanan, it il not the imme-
date picture of the sun, but reflection
refracted into the stone by the direct rays
OF old Sol, which may serve TO remind US
that The ancients knew a thing or two after
an.-St. Louis Republic.