Dear Ian Kenyon,
 
I am not very knowledgeable about glass canes, but I did learn from a PhD
student in American Studies here at Boston University that canes/walking
sticks were considered spiritually potent in African-American culture; he
showed me an example of a wooden stick with a blue glass bead inset into
it, as well as many other fascinating examples of conjuring sticks, etc.
He is doing his dissertation on African-American decorative arts and
material culture.  If you are interested in contacting him (I realize his
research may be on a different tangent than yours), his name is Theodore
Landsmark; address: American and New England Studies Program, Boston
University, 226 Bay State Road, Boston, MA 02215.
 
What you have learned thus far about canes, glass, and folk beliefs is
fascinating.  I hope colleagues more informed than I can add more than my
tidbit!
 
Cheers,
Mary Beaudry
Archaeology
Boston University
 
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