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出典:Wiktionary
出典:『Wiktionary』 (2014/01/21 05:56 UTC 版)
reading stone (複数形 reading stones)
出典:Wikipedia
出典:『Wikipedia』 (2011/04/20 04:44 UTC 版)
A reading stone was an approximately hemispherical lens that was placed on top of text to magnify the letters so that people with presbyopia could read it more easily. Reading stones were among the earliest common uses of lenses.
reading stone