Enquire within upon everything by Robert Kemp Philp

353. Breaking Glass.

Easy method of breaking glass to any required Figure.--Make a small notch by means of a file on the edge of a piece of glass, then make the end of a tobacco-pipe, or of a rod of iron of the same size, red hot in the fire, apply the hot iron to the notch, and draw it slowly along the surface of the glass in any direction you please: a crack will follow the direction of the iron.