Birmingham.
The error of Coleridge, alluded to by your correspondent ALPHAGE, is
certainly not a little singular, especially as the word, in the sense of
stone or marble, occurs in Ben Jonson, Drayton, and Sir John Harrington,
and there is a good article on the word in Nares's _Glossary_. I must,
however, altogether dissent from your correspondent's statement that the
reason for the name of Touchstone is, that a musical sound may be produced
by touching it sharply with a stick, and agree with Nares that it obtained
its name from being used as a test for gold. See a very interesting article
on Assay Marks by Mr. Octavius Morgan (_Archæological Journal_, ix. 127.),
from which it appears that, for the trial of gold, touch-needles were
applied to the touchstone.