Smithsonian Institution · Washington : Smithsonian Institution · leaf 153
preparation of the iron tools on which the grinding is to be finished is very laborious where personal exertion is used. They require to be cast thin in order that they may be easily handled, and hence cannot be turned with very great exactness, The pair for my large mirrors are 155 inches in… … The Iron Grinder, pounds apiece. Four ears, with a tapped hole in each, project at equal distances round the edge, and serve either as a means of attachment for a counterpoise lever, or as handles. ; After these were turned and taken off the lathe chuck, they were found to be somewhat sprung, and…
Science
Internet Archive · Smithsonian Libraries · Public domain (published before 1931). Free to use for anything.
