A reading stone was an approximately hemispherical transparent object placed on top of text to magnify the letters so that people with presbyopia could read the text more easily. Magnification is the process of enlarging something only in appearance not in physical size Presbyopia (Greek word "presbys" (πρέσβυς meaning "old person" describes the condition where the Eye exhibits a progressively diminished ability Reading stones were among the earliest common uses of lenses. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging
Reading stones were said to be invented by Abbas Ibn Firnas, in 8th century Córdoba, Spain, who had devised a way to finish sand into glass[1]; which until this time, was secret to the Egyptians. Abbas Ibn Firnas (810 &ndash 887 AD) was also known as Abbas Qasim Ibn Firnas and العباس بن فرناس ( Arabic language) ||-||-||} Córdoba ( Cordova in English is a City in Andalusia, southern Spain, and the capital of the province of Córdoba. This article is about the contemporary North African ethnic group These glasses could be shaped and polished into stones used for viewing - known as reading stones. These spread to the rest of Europe from approximately the 11th century onwards. The function of reading stones was replaced by the use of spectacles from the late 13th century onwards, but modern implementations are still used. Glasses, also called eyeglasses or spectacles, are frames bearing lenses worn in front of the Eyes normally for vision correction, In their modern form, they can be found as rod-shaped magnifiers, flat on one side, that magnify a line of text at a time; or as a sheet in the form of a Fresnel lens placed over an entire page. A Fresnel lens (pronounced or) is a type of lens invented by French physicist Augustin-Jean Fresnel. The modern forms are usually made of plastic.
Early reading stones were manufactured from rock crystal (quartz) or beryl as well as glass. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in The Mineral beryl is a Beryllium Aluminium cyclosilicate with the Chemical formula Be3Al2(SiO36
The Visby lenses may have been reading stones. The Visby lenses are a collection of lens -shaped manufactured objects made of Rock crystal (quartz found in a Viking grave in Gotland dating
External links
- A good illustration of a reading stone in use. Zeiss Optical Museum, Oberkochen. Retrieved on 2007-03-06. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1079 - Omar Khayyám completes the Iranian calendar. 1454 - Thirteen Years' War: Delegates of
References
- ^ Lynn Townsend White, Jr. (Spring, 1961). Lynn Townsend White Jr ( April 29 1907 – March 30 1987) was a professor of medieval History at Princeton, "Eilmer of Malmesbury, an Eleventh Century Aviator: A Case Study of Technological Innovation, Its Context and Tradition", Technology and Culture 2 (2), pp. 97-111.
"Ibn Firnas was a polymath: a physician, a rather bad poet, the first to make glass from stones (quartz?), a student of music, and inventor of some sort of metronome. Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in A metronome is any device that produces a regulated aural visual or tactile pulse to establish a steady Tempo in the performance of music "
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