lect the leaves
of the Sibyl than the titles of the works written by Roger Bacon; and
though the labour has been somewhat lightened by the publications of Brewer
and Charles, referred to below, it is no easy matter even now to form an
accurate idea of his actual productions. An enormous number of MSS. are
known to exist in British and French libraries, and probably not all have
yet been discovered. Many are transcripts of works or portions of works
already published and, therefore, require no notice.[2]

The works hitherto printed (neglecting reprints) are the following:--(1)
_Speculum Alchimiae_ (1541)--translated into English (1597); French, A
Poisson (1890); (2) _De Mirabili Potestate Artis et Naturae_
(1542)--English translation (1659); (3) _Libellus de Retardandis Senectutis
Accidentibus_ (1590)--translated as the "Cure of Old Age," by Richard Brown
(London, 1683); (4) _Sanioris Medicinae Magistri D. Rogeri Baconis Anglici
de Arte Chymiae Scripta_ (Frankfort, 1603)--a collection of small tracts
containing _Excerpta de Libra Avicennae de Anima_, _Breve Breviarium_,
_Verbum Abbreviatum,_[3] _Secretum Secretorum_, _Tractatus Trium Verborum_,
and _Speculum Secretorum_; (5) _Perspectiva_ (1614), which is the fifth
part of the _Opus Majus_; (6) _Specula Mathematica_, which is the fourth
part of the same; (7) _Opus Majus ad Clementem IV._, edited by S. Jebb
(1733) and J. H. Bridges (London, 1897); (8) _Opera hactenus Inedita_, by
J. S. Brewer (1859), containing the _Opus Tertium_, _Opus Minus_,
_Compendium Studii Philosophiae_ and the _De Secretis Operibus Naturae_;
(9) _De Morali Philosophia_ (Dublin, 1860, see below); (10) _The Greek
Grammar of R. Bacon and a Fragment of his Hebrew Grammar_, edited with
introduction and notes by E. S. Nolan and S. A. Hirsch (1902); (11)
_Metaphysica Fratris Rogeri_, edited by R. Steele, with a preface (1905);
(12) _Opera hactenus inedita_, by Robert Steele (1905).

How these works stand related to one another can only be determined by
internal evidence. The smaller works, chiefly on alchemy, are unimportant,
and the dates of their composition cannot be ascertained. It is known that
before the _Opus Majus_ Bacon had already written some tracts, among which
an unpublished work, _Computus Naturalium_, on chronology, belongs probably
to the year 1263; while, if the dedication of the _De Secretis Operibus_ be
authentic, that short treatise must have been composed before 1249.

It is, howeve