_Opus Minus_, written in 1266-7, was mainly an abstract of the _Opus Majus_ with some additions on the state of scholasticism, on alchemy practical and speculative, and on astronomy. Charles gives the following description of it. It consisted of 6 parts: i. Introduction or dedicatory letter; ii. Practical alchemy; iii. Explanation of the _Opus Majus_; the order of the sciences inverted, i.e. they were arranged according to their dignity, moral philosophy first; iv. Treatise on the seven sins of Theology; v. Speculative alchemy, or, _De rerum generationibus_ (see below); vi. _De Coelestibus_. Of this work only the fragment edited by Brewer (_Opera Ined._ 311-390) from MS. Bodl. Digby 218, has been discovered. This includes a few pages of Part ii., all of iii., most of iv., and part of v. Wood quotes a passage from the _Opus Minus_ which does not occur in this fragment (_Opera Ined._ xciv. n. 1). From this it has been assumed that he had access to a MS. of the _Opus Minus_ now lost; but the passage is quoted by Leland, and probably copied from him by Wood. It may perhaps occur in some other work of Bacon’s; thus the passage quoted in _Op. Ined._ pp. xcvii-xcviii, from which Brewer argues that ‘Wood must have seen some other copy of the _Opus Minus_ not now discoverable,’ occurs in Brewer’s edition of the _Opus Tert._ pp. 272-3. Part of the blank on p. 375 is to be filled up from the _Opus Majus, Pars VI, Exemplum II_, where the passage ‘_Est autem--curabit et_’ occurs, word for word. How much of the _Opus Majus_ was here inserted is doubtful; probably to the end of _Exemplum II_. Thus MS. Bodl. Canonic. Miscell. 334, f. 53, begins with the words, ‘_Corpora vero Adae et Evae_,’ _Opus Minus_, p. 373, and leaves off with the words, ‘_et alibi multis modis_,’ which occur at the end of _Opus Majus, Pars VI, Exemp. II_. The last part of the _Opus Minus_ is wholly wanting in Brewer’s edition. The subject of this part may be gathered from Bacon’s words in _Opus Tert._, cap. xxvi (p. 96): ‘Nunc igitur tangam aliquas radices circa haec quas diligentius exposui in Secundo Opere, ubi de coelestibus egi’: and (p. 99) ‘Sed in Opere Minore ubi de coelestibus tractavi, exposui magis ista.’ In Digby MS. 76, fol. 36 seq. (sec. xiii) is a treatise on this subject, forming part of the _Physics_ in the great _Compendium Philosophiae_ (see below). It is not improbable, that, before being incorporated in this larger work, it formed part of the _Opus Minus_ sent to the Pope; on fol. 42 are the words: ‘et est nunc temporis scilicet anno domini 1266.’ _Opus Tertium_, written in 1267 (see _Opera Ined._ p. 277), 75 chapters. MSS. London:--Brit. Mus: Cotton Tiberius C. V. (sec. xiv); also Lambeth Palace Library, 200 (chapters 1-45). Oxford:--Bodl. E Musaeo 155 (sec. xv ineuntis); and Univ. Coll. 49 (A. D. 1617). Cambridge:--Trinity College, MS. Gale (transcript of the Cotton MS.).