vitrified. They are kindled by the heat produced by the collision; but
their vivid light, and their fusion and vitrification are the effects of
a combustion continued in these particles during their passage through
the air. This opinion is confirmed by an experiment of Mr. Hawksbee, who
found that these sparks could not be produced in the exhausted receiver.
See Keir's Chemical Dict. art. Iron, and art. Earth vitrifiable.]

[_The pale Phosphor_. l. 232. See additionable notes, No. X.]


3. "YOU taught mysterious BACON to explore
Metallic veins, and part the dross from ore;
With sylvan coal in whirling mills combine
240 The crystal'd nitre, and the sulphurous mine;
Through wiry nets the black diffusion strain,
And close an airy ocean in a grain.--
Pent in dark chambers of cylindric brass
Slumbers in grim repose the sooty mass;
245 Lit by the brilliant spark, from grain to grain
Runs the quick fire along the kindling train;
On the pain'd ear-drum bursts the sudden crash,
Starts the red flame, and Death pursues the flash.--
Fear's feeble hand directs the fiery darts,
250 And Strength and Courage yield to chemic arts;
Guilt with pale brow the mimic thunder owns,
And Tyrants tremble on their blood-stain'd thrones.


[_And close an airy ocean_. l. 242. Gunpowder is plainly described in
the works of Roger Bacon before the year 1267. He describes it in a