Messrs. Hughes and Co. at the Cockpit Glasshouse, opposite St.
Paul’s.
A Set of musical Glasses, such as Mr. Franklin had, of the
following Dimensions
The upright of the Sides to be in the smallest
¾ of an Inch, adding a ¼ of an Inch to every larger Size, so that
the upright of the largest will be 3½ Inches.
Mr. Barnes is desired to take Notice, that the
Glasses are not to be made hollowing up, like those Mr. Franklin
had last, but like those he had first with Bottoms nearly even.
To fix them I us’d a Frame like the Figure in
the Margin with an upright Iron Rod, on which was a Screw from End
to End; The Rod turn’d on it’s Point.
The Bottom Board had a Number of concentric
Circles.
I had a Number of Brass female Screws, about an
Inch long.
One of these was to be cemented in the Neck of
each Glass.
On the Board I plac’d a round bit of Card a
little bigger than the Neck of the Glass, then the female Screw
upon that, then turn’d the Glass down with its Edge upon the
Circles, then put the Screw Rod thro’ the Neck of the Glass and
enter’d the female Screw, and drew it up with the Card till it came
into the Neck of the Glass, the Card coming close to stop the Neck;
then having center’d the Glass, I pour’d in the Cement. When cold,
remov’d that Glass; and plac’d another. The Neck of the Glass
should be a little warm’d, and the Cement not too hot.
When the Glasses were all furnish’d with Screws
in their Necks; I put them on the Rod, a thin Piece of Cork between
their Necks to screw them hard upon, and prevent Jarring and make
each Screw water-tight.