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.
In the same publication for 1844 and 1850 he communicated short descriptions and drawings of some of the more interesting nebulae, and in the volume for 1861 he published a paper "On the Construction of Specula of 6-ft.
From these come the bronze cistae and specula with partly (but far from wholly) Etruscan inscriptions, for which Praeneste is renowned" (Conway, Ital.
After much experiment he selected an alloy of tin and copper as the most suitable material for his specula, and he devised means for grinding and polishing them.
Bradley and Molyneux, having been instructed by Hadley in his methods of polishing specula, succeeded in producing some telescopes of considerable power, one of which had a focal length of 8 ft.; and, Molyneux having communicated these methods to Scarlet and Hearn, two London opticians, the manufacture of telescopes as a matter of business was commenced by them (Smith's Opticks, bk.
In Short's first telescopes the specula were of glass, as suggested by Gregory, but he afterwards used metallic specula only, and succeeded in giving to them true parabolic and elliptic figures.
Indeed, in its practical form the principle of the instrument has remained unchanged from the time of the Dollonds to the present day; and the history of its development may be summed up as consisting not in new optical discoveries but in utilizing new appliances for figuring and polishing, improved material for specula and lenses, more refined means of testing, and more perfect and convenient methods of mounting.
About the year 1774 William Herschel, then a teacher of music in Bath, began to occupy his leisure hours with the construction of specula, and finally devoted himself entirely to their construction and use.
In 1778 he had selected the chef-d'oeuvre of some 400 specula which he made for the celebrated instrument of 7-ft.
The composition of metallic specula in the present day differs very little from that used by Sir Isaac Newton.
The process of casting and annealing, in the case of the specula of the great Melbourne telescope, was admirably described by Dr Robinson in Phil.
Shaping, polishing and figuring of specula are accomplished by methods and tools very similar to those employed in the construction of lenses.
Xliv., February 1857), proposed to employ glass for the specula of telescopes, the reflecting surface of the glass speculum to be covered with silver by Liebig's process.
Those silver-on-glass specula are now the rivals of the achromatic telescope, and it is not probable that many telescopes with metal specula will be made in the future.
Despite the fact that their philosophic interests lay rather in ethics and physics, their activity The in what they classified as the third department of specula Stoics.
Uranus was recognized specula of continually augmented size, up to a diameter 4 p pp Herschel.
§ 45, "specula optima apud majores fuerunt Brundusiana, stanno et aere mixtis").