There is nothing about this in the third part of the Opus Majus; but it is found in the Communia Naturalium. The treatise De multiplicatione specierum was therefore part of a work of which the Communia Naturalium formed the third part. This large work was according to Jebb, the Opus Minus; according to Charles, the Opus Tertium[1350]; according to Brewer, the encyclopaedic Compendium Philosophiae. Brewer is no doubt right; the De multiplicatione was intended as a sub-section of the great treatise on Physics.
How then did the treatise come to be regarded as part of the Opus Majus, and to be inserted in the MSS. of that work? There can be little doubt that it was, in its original form, the treatise on rays sent to the Pope with the Opus Majus, but as a separate work (Opera Ined. pp. 227, 230). The references to the Communia Naturalium are not inconsistent with this hypothesis: (1) the treatise on rays does not seem to have been written specially for the Pope, and consequently references to works which he could not know were not unnatural; (2) Bacon had already begun the encyclopaedic work, but found it impossible to get it finished or send it to the Pope (Opera Inedita, pp. 60, 315).
Inc. ‘Primum igitur capitulum circa influentiam agentis habet tres veritates.’
MSS. London:—Brit. Mus.: Royal 7 F viii. f. 13; inc. ‘Postquam habitum,’ &c. Addit. 8786, fol. 20 b: inc. ‘Postquam habitum est de principiis rerum naturalium’: Sloane 2156, f. 40 (A. D. 1428); inc. ‘Postquam,’ &c.
Oxford:—Bodl. Digby 235, p. 305 (inserted in the Opus Majus).
Dublin:—Trinity Coll. 81 (in the Opus Majus).
Paris:—Bibl. Nat. 2598 (sec. xv): inc. ‘Postquam,’ &c.
Bruges, 490 (sec. xiii), called Philosophia Baconis.
Printed in Jebb.
De speculis (on burning mirrors). Inc. ‘Ex concavis speculis ad solem positis ignis accenditur.’