HYDROPHANE. 
411 
The younger Saussure has found an ingenious 
Way to render the hydrophane transparent by heat 
as well as moisture. This stone is evidently of a 
porous nature, and merely becomes transparent by 
having its pores filled with a fluid ; therefore Saus- 
sure plunged a specimen of the hydrophane into 
melted wax, and succeeded with his experiment. 
When the wax was cold and congealed, the stone 
was opaque : on the contrary, when the wax be- 
came fluid by heat, it was transparent. Among 
other experiments tried with this stone, it has been 
found that when plunged in hot water it becomes 
transparent much sooner, and that the same hap- 
pens when it is put into very dilute acid. As a 
proof of the porosity of the hydrophane, Patrin 
mentions one of an inch in diameter, which is en- 
tirely opaque, but acquires in water the transpa- 
rency and colour of a topaz of Saxony. When it 
is dry and opaque, it weighs 135 grains; but when 
it becomes transparent in water it is found to have 
acquired eight grains, as it then weighs 143. An- 
other of 126 grains when dry is found to increase 
in the same proportion after it has been for some 
time in water, where it becomes of an orange 
colour. 
Hydrophanes are found in the same situation as 
the chalcedony and the opal. The places which 
are particularly noticed for producing these stones, 
are Hubertsburg in Saxony, the Isle of Ferro, Tel- 
kobania in Hungary, Chatelaudren in France, and 
the mountain of Musinet, two leagues to the west 
