_Alchemy_ was treated in the _Opus Minus_ and in the _Compendium Philosophiae_. Bacon divides it into (1) Speculative alchemy, ‘the science of the generation of things from elements’; (2) Practical alchemy, ‘which teaches us how to make noble metals and colours,’ &c., and the art of prolonging life (_Opus Tertium_, cap. xii). Wood mentions a treatise of Bacon’s _De rerum generationibus_, of which he had seen two copies varying much. These may have been the versions in the _Opus Minus_[1356] and the _Compendium Philosophiae_[1357]. A number of works on alchemy and medicine ascribed to Bacon have been preserved, some of them are undoubtedly genuine, others apocryphal. _Epistolae fratris Rogerii Baconis de secretis operibus artis et naturae et de nullitate magiae_ [or, _De mirabili potestate artis et naturae_]. The work consists of a letter or collection of letters in ten or eleven chapters, the last five of which Charles considers doubtful, addressed perhaps to William of Auvergne (who died in 1248), or to John of London, whom Charles identifies with John of Basingstoke (d. 1252). _Inc. cap._ 1. ‘Vestrae petitioni respondeo diligenter. Nam licet.’ MS. Brit. Mus: Sloane 2156, p. 117. Printed at Paris 1542; at Oxford 1594; Hamburg 1613; in Zetzner’s _Theatrum Chemicum_, 1659; and by Brewer in _Rog. Bacon Opera Inedita_, App. I. The three following treatises were printed at Frankfurt in 1603, under the title, _Sanioris medicinae magistri D. Rogeri Baconis angli de arte chymiae scripta_, &c., and elsewhere. Summary of Avicenna’s _De anima_. _Inc._ ‘In illius nomine qui major est.’ MS. Bodl: Ashmole 1467 (sec. xvi). [Cf. Charles, _R. Bacon_, p. 59; _Opera Ined._ p. 39.] _Breve Breviarium_, or, _De naturis metallorum in ratione alkimica et artificiali transformatione_, or, _Coelestis alchymia_, or, _De naturis metallorum et ipsorum transmutatione_. Divided into two parts, speculative and practical alchemy; the work contains no doubt some of the ideas incorporated in the _Opus Minus_ and the _Comp. Philosophiae_. The date is uncertain. _Inc._ ‘Breve breviarium breviter abbreviatum.’ MSS. Brit. Mus: Sloane 276, f. 4 (sec. xv-xvi). Bodl.: Digby 119, fol. 64 (sec. xiv); and Bodl. E Musaeo 155, p. 513. Paris:--Bibl. Nat. new Latin collection, No. 1153. (Abbey of St. Germain). _Tractatus trium verborum_, or, _Epistolae tres ad Johannem Parisiensem_; namely: i. ‘De separatione ignis ab oleo,’ or, ‘De modo projectionis’; ii. ‘De modo miscendi’; iii. ‘De ponderibus.’ _Inc._ ‘Cum ego Rogerus rogatus a pluribus.’ MSS. British Museum: Cotton Julius D. V.; Harleian 3528, f. 174; Sloane 1754, ‘Mendacium primum, secundum, et tertium.’ Oxford:--Bodl: Digby 119, f. 82 (sec. xiv ineuntis); Ashmole 1448, pp. 1-25 (sec. xv); Corpus Christi Coll. 125, f. 84{b}; University Coll. 49. _Fragment on alchemy_, without title.