Appleton's dictionary of machines, mechanics, engine-work, and engineering (1869)
New York, Appleton · leaf 620
ey subtend Thia polygon hasa sufficient number of Bides to enable it to give,^il the angle formed by the junction of two of them, alight not very much inferior to what is produced in the centre of one of the sides; and the upplower courses of carved mirrors are always so placed as partly to make up…
Mechanical engineering
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
