Talk:James Short (mathematician)

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"...and thus succeeded in giving them true parabolic and elliptic shapes"?

Under the heading "Telescope Manufacture" the third sentence of the first paragraph states "In Short's first telescopes the specula were made of glass, as suggested by James Gregory, however later he used metallic specula only, and thus succeeded in giving them true parabolic and elliptic shapes" (emphasis added).
I'm not an expert in the history of telescopes, although I am familiar with the process of making both speculum metal mirrors and silvered glass mirrors, and the process for grinding the profile of the blank is approximately the same; both glass and speculum metal can be ground into parabolic/elliptic profiles. I believe that the phrase "...and thus succeeded in...", implying that it was possible in one material but not the other is, I believe, nonsensical. Furthermore, no mention is made of Short's process for the silvering of glass mirrors (before he switched to speculum metal). In the 1730s, when Short began, mirror silvering was done with an amalgam of mercury and tin, and was unsuitable for telescope mirrors as its reflectivity was poor. It wasn't until 1835 that Liebig discovered how to coat glass with actual silver (which had its own shortcomings), and the process for coating glass with aluminum (the method still used today) wasn't discovered until 1930. Could someone more knowledgeable than I please check the aforementioned claim for accuracy?
Bricology (talk) 17:53, 7 November 2024 (UTC)[reply]