Rogeri Baconis Anglici de Arte Chymiae Scripta (Frankfort, 1603) - a collection of small tracts containing Excerpta de Libro 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.
The so-called first edition of the Speculum Majus, including the Speculum Morale, ascribed to Johann Mentelin and long celebrated as the earliest work printed at Strassburg, has lately been challenged as being only an earlier edition of Vincent's three genuine Specula (c. 1468-70), with which has been bound up the Speculum Morale first printed by Mentelin (c. 1 473-7 6).
The Specula Melitensis Encyclica (1638) gives an account of a kind of calculating machine of his invention.
The first constructor of reflecting telescopes on a large scale, William Herschel, never published anything about his methods of casting and polishing specula, and he does not appear to have been very successful beyond specula of 18 in.
Hitherto it had been felt as a great difficulty in casting specula that the solidification did not begin at one surface and proceed gradually to the other, the common sand mould allowing the edges to cool first, so that the central parts were subject to great straining when their time of cooling came, and in large castings this generally caused cracking.