mercuric oxide by heating
mercury. This type of experiment contributed to the discovery of "
dephlogisticated air" by Priestley, which became better known as oxygen, following Lavoisier's investigations.
Chapter 17 of
William Bates' 1920 book ''Perfect Sight Without Glasses'', in which the author argues that observation of the sun is beneficial to those with poor vision, includes a figure of somebody "Focussing the Rays of the Sun Upon the Eye of a Patient by Means of a Burning Glass."
Use
War: since the legend of Archimedes
The first use of a burning glass by Archimedes was for the purpose of war, with the burning glass being as a weapon in 212 BC, when Syracuse was besieged by Marcus Claudius Marcellus. The Roman fleet was supposedly incinerated, though eventually the city was taken and Archimedes was slain.
In 1796, during the
French Revolution
The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in November 1799. Many of its ideas are conside ...
and three years after the declaration of war between France and Great Britain, physicist
Étienne-Gaspard Robert
Étienne-Gaspard Robert (15 June 1763 – 2 July 1837), often known by the stage name of "Robertson", was a prominent Liégeois (now part of Belgium) physicist, stage magician and influential developer of phantasmagoria. He was described by C ...
met with the French government and proposed the use of mirrors to burn the invading ships of the British
Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against Fr ...
. They decided not to take up his proposal.
[Burns, Paul. ]
The History of The Discovery of Cinematography: Chapter Six, 1750–1799
. Accessed 29 July 2007.
Domestic use: primitive fire making
Burning glasses (often called fire lenses) are still used to light fires in outdoor and primitive settings. Large burning lenses sometimes take the form of
Fresnel lens
A Fresnel lens ( ; ; or ) is a type of composite compact lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships."
The design allows the c ...
es, similar to
lighthouse
A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways.
Lighthouses m ...
lenses, including those for use in
solar furnaces. Solar furnaces are used in industry to produce extremely high temperatures without the need for fuel or large supplies of electricity. They sometimes employ a large
parabolic array of mirrors (some facilities are several stories high) to focus light to a high intensity.
Religion: sacred fire
In various religions settings, a burning glass is used to set off some sort of
sacred fire.
From the 7th to the 16th centuries, a burning glass was used by Christians to set off the
Easter Fire during the
Easter vigil. Thus,
Saint Boniface
Boniface, OSB ( la, Bonifatius; 675 – 5 June 754) was an English Benedictine monk and leading figure in the Anglo-Saxon mission to the Germanic parts of the Frankish Empire during the eighth century. He organised significant foundations o ...
explained to
Pope Zachary
Pope Zachary ( la, Zacharias; 679 – March 752) was the bishop of Rome from 28 November 741 to his death. He was the last pope of the Byzantine Papacy. Zachary built the original church of Santa Maria sopra Minerva, forbade the traffic of sla ...
that he produced the new fire of Holy Saturday by means of a crystal lens concentrating the rays of the sun. This process was also mentioned in liturgical books until the
Roman Pontifical of 1561.
In
Cambodia
Cambodia (; also Kampuchea ; km, កម្ពុជា, UNGEGN: ), officially the Kingdom of Cambodia, is a country located in the southern portion of the Indochinese Peninsula in Southeast Asia, spanning an area of , bordered by Thailand ...
, a burning glass has also been used since ancient times for the
cremation
Cremation is a method of Disposal of human corpses, final disposition of a Cadaver, dead body through Combustion, burning.
Cremation may serve as a funeral or post-funeral rite and as an alternative to burial. In some countries, including India ...
of kings and most recently for the funeral of
King Sihanouk
Norodom Sihanouk (; km, នរោត្តម សីហនុ, ; 31 October 192215 October 2012) was a Cambodian statesman, Sangkum and FUNCINPEC politician, film director, and composer who led Cambodia in various capacities throughout his ...
. The crematorium of the king is traditionally prepared by the
Bakus brahmin from the
Royal Palace
This is a list of royal palaces, sorted by continent.
Africa
* Abdin Palace, Cairo
* Al-Gawhara Palace, Cairo
* Koubbeh Palace, Cairo
* Tahra Palace, Cairo
* Menelik Palace
* Jubilee Palace
* Guenete Leul Palace
* Imperial Palace- ...
on the last day of the week-long funeral. Small pieces of fragrant
agarwood are placed beneath the magnifying glass until it ignites. The incandescent wood is used to light candles and pass on the fire to the attendees, who usually take their lit candles home.
Sports: lighting the Olympic torch
The
Olympic torch that is carried around the host country of the
Olympic Games
The modern Olympic Games or Olympics (french: link=no, Jeux olympiques) are the leading international sporting events featuring summer and winter sports competitions in which thousands of athletes from around the world participate in a multi ...
is lit by a burning glass, at the site of ancient
Olympia in
Greece
Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders wi ...
.
Popular culture: verification attempts
There have been several real-world tests to evaluate the validity of this myth over the centuries, including a test by
Comte de Buffon
Georges-Louis Leclerc, Comte de Buffon (; 7 September 1707 – 16 April 1788) was a French naturalist, mathematician, cosmologist, and encyclopédiste.
His works influenced the next two generations of naturalists, including two prominent F ...
(circa 1747), documented in the paper titled "Invention De Miroirs Ardens, Pour Brusler a Une Grande Distance", and an experiment by John Scott, which was documented in an 1867 paper.
In 1973, Greek scientist Dr. Ioannis Sakkas, curious about whether Archimedes could really have used a "burning glass" to destroy the Roman fleet in 212 BC, lined up nearly 60 Greek sailors, each holding an oblong mirror tipped to catch the sun’s rays and direct them at a wooden ship 160 feet away. The ship caught fire at once. Sakkas said after the experiment there was no doubt in his mind the great inventor could have used bronze mirrors to scuttle the Romans.
However, accounting for battle conditions makes such a weapon impractical, with modern tests refuting such claims. An experiment was carried out by a group at the
Massachusetts Institute of Technology
The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of th ...
in 2005. It concluded that although the theory was sound for stationary objects, the mirrors would not likely have been able to concentrate sufficient
solar energy
Solar energy is radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy (including solar water heating), and solar architecture. It is an essen ...
to set a ship on fire under battle conditions. Similar experiments were conducted on the popular science-based TV show ''
MythBusters
''MythBusters'' is a science entertainment television program, developed by Peter Rees and produced by Australia's Beyond Television Productions. The series premiered on the Discovery Channel on January 23, 2003. It was broadcast internation ...
'' in
2004
2004 was designated as an International Year of Rice by the United Nations, and the International Year to Commemorate the Struggle Against Slavery and its Abolition (by UNESCO).
Events January
* January 3 – Flash Airlines Flight ...
,
2006
File:2006 Events Collage V1.png, From top left, clockwise: The 2006 Winter Olympics open in Turin; Twitter is founded and launched by Jack Dorsey; The Nintendo Wii is released; Montenegro votes to declare independence from Serbia; The 2006 ...
, and
2010
File:2010 Events Collage New.png, From top left, clockwise: The 2010 Chile earthquake was one of the strongest recorded in history; The Eruption of Eyjafjallajökull in Iceland disrupts air travel in Europe; A scene from the opening ceremony of ...
, arriving at similar results based on the premise of the controversial myth.
However, an episode of ''
Richard Hammond's Engineering Connections
''Richard Hammond's Engineering Connections'' is a British documentary series originally broadcast on the National Geographic Channel, and later on BBC2. It is presented by Richard Hammond, and looks at how engineers and designers use historic ...
'' relating to the
Keck Observatory
The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when ...
(whose reflector glass is based on the Archimedes' Mirror) did successfully use a much smaller curved mirror to burn a wooden model, although the scaled-down model was not made of the same quality of materials as in the ''MythBusters'' effort.
See also
*
Diocles (mathematician)
*
Nimrud lens
*
Pyreliophorus The Pyreliophorus was a device similar to a burning glass, created by the Portuguese priest Manuel António Gomes, also known as ''padre Himalaya'', whose objective was to melt many different types of materials using solar energy. The device used s ...
*
Visby lenses
*
Solar furnace
References
Further reading
*Temple, Robert. ''The Crystal Sun'', .
External links
*
{{DEFAULTSORT:Burning Glass
Magnifiers
Lenses
Ancient weapons