125 "Thus, cavern'd round in CRACOW'S mighty mines, With crystal walls a gorgeous city shines; Scoop'd in the briny rock long streets extend Their hoary course, and glittering domes ascend; Down the bright steeps, emerging into day, 130 Impetuous fountains burst their headlong way, O'er milk-white vales in ivory channels spread, And wondering seek their subterraneous bed. Form'd in pellucid salt with chissel nice, The pale lamp glimmering through the sculptured ice, 135 With wild reverted eyes fair LOTTA stands, And spreads to Heaven, in vain, her glassy hands; Cold dews condense upon her pearly breast, And the big tear rolls lucid down her vest. Far gleaming o'er the town transparent fanes 140 Rear their white towers, and wave their golden vanes; Long lines of lustres pour their trembling rays, And the bright vault returns the mingled blaze. 2. "HENCE orient NITRE owes it's sparkling birth, And with prismatic crystals gems the earth, 145 O'er tottering domes in filmy foliage crawls, Or frosts with branching plumes the mouldering walls. As woos Azotic Gas the virgin Air, And veils in crimson clouds the yielding Fair, Indignant Fire the treacherous courtship flies, 150 Waves his light wing, and mingles with the skies. [_Hence orient Nitre_. l. 143. Nitre is found in Bengal naturally crystallized, and is swept by brooms from earths and stones, and thence called sweepings of nitre. It has lately been found in large quantities in a natural bason of calcareous earth at Molfetta in Italy, both in thin strata between the calcareous beds, and in efflorescences of various beautiful leafy and hairy forms. An account of this nitre-bed is given by Mr. Zimmerman and abridged in Rozier's Journal de Physique Fevrier. 1790. This acid appears to be produced in all situations where animal and vegetable matters are compleatly decomposed, and which are exposed to the action of the air as on the walls of stables, and slaughter-houses; the crystals are prisms furrowed by longitudinal groves. Dr. Priestley discovered that nitrous air or gas which he obtained by dissolving metals in nitrous acid, would combine rapidly with vital air, and produce with it a true nitrous acid; forming red clouds during the combination; the two airs occupy only the space before occupied by one of them, and at the same time heat is given out from the new combination. This dimunition of the bulk of a mixture of nitrous gas and vital air, Dr. Priestley ingeniously used as a test of the purity of the latter; a discovery of the greatest importance in the analysis of airs. Mr. Cavendish has since demonstrated that two parts of vital air or oxygene, and one part of phlogistic air or azote, being long exposed to electric shocks, unite, and produce nitrous acid. Philos. Trans. Vols. LXXV. and LXXVIII.