80 bernard vitrac
attributable to Th eon of Alexandria. In fact, we have a (single) example of
this authorial division. Th eon indicates explicitly, in his Commentary to
the Almagest , that he had been given an edition of the Elements and that
he had modifi ed the last Proposition of Book vi ( vi .33 Heib.) in order
to append an assertion concerning proportionality of sectors and arcs
upon which they stand in equal circles. Zamberti’s attribution of proofs
to Th eon was undoubtedly inferred from the glosses ‘of the edition of
Th eon (ἐκ τῆς Θέωνος ἐκδοσεως)’ marked on the Greek manuscripts
used by him. Consequently, since it was understood that Th eon had
re-edited the Elements in the second half of the fourth century of our
era, the question arose of what ought to be ascribed to Euclid and what
ought to ascribed to the editorial actions of Th eon. For someone like
R. Simson (1756), the answers were particularly clear. All that was
worthy of admiration originated with Euclid; all the defi ciencies were
due to the incompetence of the re-editor.
Th us, the debate on the subject was open. When F. Peyrard, around
1808, undertook to check the Greek text for his new French translation
of Elements which was based on the Oxford edition of 1703, he discov-
ered among the manuscripts which had been brought back from Italy by
Gaspard Monge (aft er the Napoleonic campaigns) a copy belonging to the
Vatican Library ( Va t i c a n u s g r. 190), which contained neither mention ‘of
the edition of Th eon’ nor the additional portion at vi .33 and which dif-
fered considerably from the twenty-two other manuscripts known to him.
From this divergence, he deduced that this manuscript, unlike the others,
preceded the re-edition of Th eon and that it moreover contained the text of
Euclid! 26 He at once decided to make a new edition of the Greek text.
Heiberg accepted (with some reworking) the interpretations of Peyrard,
particularly the idea that all the manuscripts with the exception of Va t i c a n u s
gr. 190 were derived from Th eon’s edition. He called these the ‘Th eonine’. 27
As for the Vatican copy, he was more careful. Heiberg noted that the copyist
admits in the margins of Proposition xi .38 vulgo 28 and Proposition xiii .6 to
have consulted two editions, one ‘ancient’ and the other ‘new’. Proposition
xiii .6 existed in the fi rst but was missing in the other. Exactly the oppo-(^26) Peyrard 1814: xiii, xxv.
(^27) Consequently, in the following, I will use the abbreviation Th to designate the aforementioned
family of manuscripts.
(^28) Several Propositions appearing in the editio princeps (and reproduced in the following
editions) were discarded by Heiberg who designated them in this way lest there be some
confusion in numbering. xi.38 vulgo was No. 38 in the preceding editions. It was rejected by
Heiberg in the Appendix. His Proposition 38 was thus No. 39 in the previous editions.