PRIESTLEY, Joseph (1733-1804). Experiments and observations on different kinds of air. London: J. Johnson, 1774-1775. 2 (of 3) volumes. Half-title in vol. I, 4pp. errata and adverts at end of vol. I, 4pp. adverts at end of vol. II. 5 engraved plates, of which 2 folding. (Lacking vol. III, marginal paper flaw to I.I3, occasional light spotting.) Crook S/451-452; Norman 1750; Wellcome IV, p.436. [With:] -- Experiments and observations relating to various branches of natural philosophy; with a continuation of the Observations on air. Vol. I, London: J. Johnson, 1779; vol. II, Birmingham: Pearson and Rollason for J. Johnson, 1781. 2 (of 3) volumes [i.e. forming continuation volumes IV and V of Observations on different kinds of air]. 2 folding engraved frontispieces, vol. II with the two additional leaves pp.*395-*398 inserted after Cc5 and with 6pp. listing of Priestley's works not mentioned in Crook. (Occasional light spotting.) Crook S/465-466; Wellcome IV, p.436 [And:] -- Disquisitions relating to matter and spirit. London: J. Johnson, 1777. Engraved frontispiece. (Lacking half-title, occasional light spotting.) Crook PM/357 (incorrectly omitting gathering Aa4 at end with pp.349-356 and [Bb2] with 4pp. listing of Priestley's works); Wellcome IV, p.436 (2nd ed.). Together 5 volumes, 8° (206 x 122mm). Uniform in contemporary half calf (all neatly rebacked to style preserving original red morocco gilt labels, extremities lightly rubbed). Provenance: occasional neat contemporary ink annotation in a contemporary hand. FIRST EDITIONS of the first two volumes of Experiments and observations on different kinds of air and the first two continuation volumes of that work, together with his first publication on philosophical and metaphysical matters. Priestley's hundreds of experiments on different types of 'air' led to the discovery of oxygen and some of its properties.