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 curious manner, mentioning the sulphur and nitre, but conceals the charcoal in an anagram. The words are, sed tamen salis petrae _lure mope can ubre_, et sulphuris; et sic facies tonitrum, et corruscationem, si scias, artificium. The words lure mope can ubre are an anagram of carbonum pulvere. Biograph. Britan. Vol. I. Bacon de Secretis Operibus, Cap. XI. He adds, that he thinks by an artifice of this kind Gideon defeated the Midianites with only three hundred men. Judges, Chap. VII. Chamb. Dict. art. Gunpowder. As Bacon does not claim this as his own invention, it is thought by many to have been of much more antient discovery. The permanently elastic fluid generated in the firing of gunpowder is calculated by Mr. Robins to be about 244 if the bulk of the powder be 1. And that the heat generated at the time of the explosion occasions the rarefied air thus produced to occupy about 1000 times the space of the gunpowder. This pressure may therefore be called equal to 1000 atmospheres or six tons upon a square inch. As the suddenness of this explosion must contribute much to its power, it would seem that the chamber of powder, to produce its greatest effect, should be lighted in the centre of it; which I believe is not attended to in the manufacture of muskets or pistols. From the cheapness with which a very powerful gunpowder is likely soon to be manufactured from aerated marine acid, or from a new method of forming nitrous acid by means of mangonese or other calciform ores, it may probably in time be applied to move machinery, and supersede the use of steam.