MS. Paris:--Bibl. Nat. 2598, f. 138 (sec. xv), ‘Explicit de subjecto transmutationis secundum Rogerum Bachonis.’ It perhaps occurs in one of his larger works. _Libellus Rogerii Baconi ... de retardandis senectutis accidentibus et de sensibus conservandis_ (11 chapters). This work is assigned by Charles to the year 1276. _Inc. prol._ ‘Domine mundi ex nobilissima stirpe originem assumpsistis.’ _Inc. cap._ 1. (De causis senectutis). ‘Senescente mundo senescunt homines.’ MSS. Brit. Museum: Sloane 2320, fol. 56. Bodl.: E Musaeo 155, pp. 591-637 (sec. xiv-xv); Canonic. Misc. 334, fol. 1 (sec. xv); and 480, fol. 1 (sec. xv). Printed at Oxford in 1596 (and in English, London 1683). _Antidotarius_, a second part of this work. _Inc._ ‘Post completum universalis sciencie medicacionis tractatum.’ MSS. Bodl.: Canonic. Miscell. 334 (fol. 21{b} to 25), and 480 (fol. 16); E Musaeo 155, p. 645. Cf. MS. Canon. Misc. 480, fol. 38{b}-47, below. _Liber Bacon de sermone rei admirabilis, sive de retardatione senectutis._ _Inc._ ‘Intendo componere sermonem rei admirabilis domino meo fratri E, cujus vitam deus prolonget.’ MSS. Bodl.: E Musaeo 155, pp. 655-666; Digby 183, fol. 45 (sec. xiv exeuntis); Canonic. Miscell. 334, fol. 25-31. _De universali regimine senum et seniorum._ _Inc._ ‘Summa regiminis senum universalis est hoc ut dicit Avicenna.’ MSS. Brit. Mus.: Sloane 2629, fol. 57. Bodl.: Canon. Miscell. 334, fol. 18{b}-21{b}; 480 (_explicit_ fol. 16); and E Musaeo 155, p. 638. _De graduacione medicinarum compositarum._ _Inc._ ‘Omnis forma inherens.’ MSS. Bodl. Canon. Misc. 334, fol. 32; 480; fol. 23{b} (the author’s name is obliterated in the MS.). _Tractatus de erroribus medicorum_[1358]. _Inc._ ‘Vulgus medicorum.’ MSS. Oxford: Bodl. Canon. Misc. 334, fol. 42; 480, fol. 30 (author’s name obliterated); E Musaeo 155, pp. 669-689. Corpus Ch. Coll. 127 (sec xv). _Canones practici de medicinis compositis componendis_, ‘Cap. i. Extractum de libro septimo Serapionis qui est antidotarium suum et est theoricum capitulum.’ (13 chapters.) _Inc._ ‘Necesse est illi qui vult componere medicinas.’ ‘Explicit tractatus de compositione medicinarum per fratrem rugerium bacon editus.’ MS. Bodl. Canon. Misc. 480, fol. 38{b}-47. _De leone viridi_ (on the manufacture of mercury); only the summary by Raymund Gaufredi is extant. _Inc._ ‘Verbum abbreviatum.’ MSS. Brit. Mus.:--Sloane 692, f. 46 (sec. xv). Oxford:--Corpus Chr. Coll. 277. Printed at Frankfurt, 1603 (_Sanioris medicinae_, p. 264), &c. A number of works on alchemy are attributed to Roger Bacon erroneously or without any probability. _De consideratione quintae essentiae_; 3 books. The author was a Franciscan who entered the Order at Toulouse[1359]. _Inc. opus._ ‘Dixit Salomon sapientie cap. vii. Deus dedit mihi.’