Up: Glassmaking
Reminiscences
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into one without fracture of the glass; even the stroke of a mallet
sufficiently heavy to drive a nail has failed to break such glasses.
In a word, ordinary blows fail to produce an impression upon articles
of this kind. If, however, a piece of flint, cornelian, diamond, or
other hard stone, fall into one of these glasses, or be shaken therein
a few moments, the vessel will fly into a myriad of pieces.
Glass of the class called
Prince Rupert Drops exhibits another
striking property. Let the small point be broken, and the whole
flies with a shock into powder. Writers have endeavored to solve
the philosophy of this phenomenon; some by attributing to it percussion
putting in motion some subtle fluid with which the essential substance of
glass is permeated, and thus the attraction of cohesion being overcome.
Some denominate the fluid electricity, and assert that it exists in glass
in great quantities, and is capable of breaking glass when well annealed.
These writers do not appear to have formed any conclusion satisfactory
to themselves, and fail to afford any well-defined solution to the
mystery.
Another phenomenon in connection with glass tubes
is recorded in the
"Philosophical Transactions,"
No. 476:—
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