Burning Glass - What Is It?
Posted on January 31, 2008 - Filed Under Education |
Burning glass is early name given to a magnifying glass that was used to light fires. Every boy scout and girl guide knows that they need to be prepared and to include a magnifying glass into his kit. The magnifying glass or burning glass concentrates the rays of light onto a small point to such a level that combustion is instigated.
There are a number of references from earlier times of burning glasses used both as a way of lighting ceremonial fires and as weapons of war. There is reference to triangular metal mirrors being used in the temple of the Vestal Virgins to light a lamp. The mathematician, Archimedes was said to have used the concept of “burning glass” to set fire to the Roman Fleet in 212 BC. The Archimedes legend as it is referred to, has been recreated a number of times during the last 2,000 years.
It is believed that he used a large number of adjustable hexagonal surfaces to concentrate the suns rays sufficiently to cause fire. Another recorded event describing the use of burning glass was in 5BC, when they were used as a defence of the Phoenician city of Gades. There are some who do not agree that “burning glasses” were used to destroy ships, and there will still no doubt be tests to prove or disprove these events in years to come. A recent ‘Mythbusters” TV show attempted to create the effect, but could not conclusively prove it.
Excavations in Sweden have provided evidence that the Vikings knew about the principles associated with “burning glass”. Rock crystal lenses have been found with imaging quality similar to the quality of the 20th century. It is believed that these crystals were ground using pole lathes. The rock crystal lenses have been thoroughly tested by scientists and they work well at producing fire.
During the French Revolution in the late 18th century, there was much discussion about using the principles of burning glass against the Royal Navy, however this option was not exercised.
Currently, the only reasonable scale use of the principles of “burning glass” is in solar furnaces, where sunlight is concentrated using a number of large mirrors to produce high heat levels. Parabolic mirrors that track the sun are usually used for this purpose. These parabolic mirrors are effectively used in heating water in some modern solar hot water systems.
The lighting of fires with magnifying glasses (used as burning glasses) will thrill children and campers for years to come. The trusty magnifying glass will operate even if it is wet!
Magnifying Glasses are sometimes a little difficult to obtain. For more information about magnifying glasses and different configurations go to http://groovyideas.googlepages.com
Tags: burning glass, large magnifying glass, lighted magnifying glass, magnifier, magnifying glass
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