46 
ROTTEN' STONE. 
(he moit, was the singular appearance of the glass in the win- 
Wiii'Jow glass dovv of a counting house attached to one of the works. The 
foirodcd, panes looked as if covered over with liquid starch, to answer 
the purpose of a blind, but, upon a nearer view, I found they 
had lost their polish, the surface exhibiting the appearance of 
gla.ss corroded by fluoric acid. Upon mentioning this circum- 
stance to a person residing near the spot, I was informed, that 
the same corroded appearance was to be observed in the win- 
dows of his own bouse, which was a quarter of a mile distant. 
Several substances have been applied to remove this misty ap- 
pearance ; wet red clay, rubbed on with the palm of the hand, 
has been found most successful j by lon^-continued friction 
with this substance, the rough surface is entirely removed, 
and the original polish restored. 
Tlie copper ores that are usually worked here are bronght 
from Cornwall. The fumes arising from roasting the ores, 
are copious and white, and continue a long time in the atmos- 
phere where they are dissipated. Their smell is sulphureous 
and excites coughing. 
' I beg to be informed, through the medium of your excellent 
Journal, what it is in the smoke that can occasion such a sin- 
gular appearance in the windows of the neighbouring houses. 
I remain, 
Sir, 
Your obedient Servant, 
VIATOR. 
Swansea, 
August 23d, 1813. 
VI. 
Cursory Remarks on the mineral Substance called, in Derbyshire, 
Rot leru Stone*. By H^ilUam Martin, F. L. S. fs’e. 
itetteu stone 
cunsiilereil as 
of volcanic 
M r. KIR wan, in his “ Elements of Mineralogy,” (vol. 
i. p. 203.) states, that Tripoli is often of pseudo-volca- 
origin. 
* Mauchc.'ter Memoirs, VIII, (or II N. J.) 
nle 
