Errata

12. Teaches a new way, of using a Telescope for drawing in proportion all the new Appearances in the Heavens; for measuring the Bodies of the Planets, and of the Fixt Stars themselves and their distances, in such parts, that a Line (the twelfth part of an inch) shall contain a 1000 of them; an inch (the twelfth part of a foot) 12000, and a foot, 144000. Besides, a very easy and certain way of making all these parts (though very small) perceptible to the bare Eye. So far of the first Head of this Third Part. The other Head is the Mechanical, shewing the several ways of Forming and Polishing all sorts of Glasses, that serve for Telescopes; which is done in six Sections. 1. Rectifies the Common way of forming Glasses Spherically, and all the Moulds, in which the Vulgar Artists are wont to work them. 2. Teaches a way of excellently forming and polishing such Glasses by hand, without any Engin. 3. Teaches a way of working Glasses by the hand guided by a simple Engin. 4. Treats of the working of Glasses by Instruments and Engins, regulating and directing the hand. 5. Teaches a New way of working Spherical Concave Eyes glasses, to serve Telescopes of the first kind, above-mentioned. 6. Teaches a New way of working all sorts of Spherical Glasses, Convex and Concave, for Telescopes, very universally, speedily, with ease, and in a small room; even for the longest Tubes. All which the Author concludes with a Direction for a way of making Tubes that may serve to fit up Telescopical Glasses. ERRATA. In Numb. 74. p. 2221. l. 25. r. is by Bruerus described to Muffet. In this Numb. 78. p. 3029. l. 22. r. predicted, for practised, p. 3029. l. 16. &c. unum. ibid. l. 25. r. spectaculum. LONDON, Printed for John Martyn, Printer to the Royal Society. 1671.