Publius Vergilius Maro called Virgil or Vergil in English, was an ancient Roman poet of the Augustan period. He wrote three of the most famous poems in Latin literature: the Eclogues, the Georgics, the epic Aeneid. A number of minor poems, collected in the Appendix Vergiliana, are sometimes attributed to him. Virgil is traditionally ranked as one of Rome's greatest poets, his Aeneid has been considered the national epic of ancient Rome since the time of its composition. Modeled after Homer's Iliad and Odyssey, the Aeneid follows the Trojan refugee Aeneas as he struggles to fulfill his destiny and reach Italy, where his descendants Romulus and Remus were to found the city of Rome. Virgil's work has had wide and deep influence on Western literature, most notably Dante's Divine Comedy, in which Virgil appears as Dante's guide through Hell and Purgatory. Virgil's biographical tradition is thought to depend on a lost biography by Varius, Virgil's editor, incorporated into the biography by Suetonius and the commentaries of Servius and Donatus, the two great commentators on Virgil's poetry.
Although the commentaries no doubt record much factual information about Virgil, some of their evidence can be shown to rely on inferences made from his poetry and allegorizing. The tradition holds that Virgil was born in the village near Mantua in Cisalpine Gaul. Analysis of his name has led to beliefs. Modern speculation is not supported by narrative evidence either from his own writings or his biographers. Macrobius says, he attended schools in Cremona, Mediolanum and Naples. After considering a career in rhetoric and law, the young Virgil turned his talents to poetry. According to Robert Seymour Conway, the only ancient source which reports the actual distance between Andes and Mantua is a surviving fragment from the works of Marcus Valerius Probus. Probus flourished during the reign of Nero. Probus reports. Conway translated this to a distance of 28 English miles. Little is known about the family of Virgil, his father belonged to gens Vergilia, his mother belonged to gens Magia. According to Conway, gens Vergilia is poorly attested in inscriptions from the entire Northern Italy, where Mantua is located.
Among thousands of surviving ancient inscriptions from this region, there are only 8 or 9 mentions of individuals called "Vergilius" or "Vergilia". Out of these mentions, three appear in inscriptions from Verona, one in an inscription from Calvisano. Conway theorized. Calvisano is located 30 Roman miles from Mantua, would fit with Probus' description of Andes; the inscription in this case is a votive offering to the Matronae by a woman called Vergilia, asking the goddesses to deliver from danger another woman, called Munatia. Conway notes that the offering belongs to a common type for this era, where women made requests for deities to preserve the lives of female loved ones who were pregnant and were about to give birth. In most cases, the woman making the request was the mother of a woman, pregnant or otherwise in danger. Though there is another inscription from Calvisano, where a woman asks the deities to preserve the life of her sister. Munatia, the woman who Vergilia wished to protect, was a close relative of Vergilia or Vergilia's daughter.
The name "Munatia" indicates that this woman was a member of gens Munatia, makes it that Vergilia married into this family. According to the commentators, Virgil received his first education when he was five years old and he went to Cremona and Rome to study rhetoric and astronomy, which he soon abandoned for philosophy. From Virgil's admiring references to the neoteric writers Pollio and Cinna, it has been inferred that he was, for a time, associated with Catullus' neoteric circle. According to Servius, schoolmates considered Virgil shy and reserved, he was nicknamed "Parthenias" or "maiden" because of his social aloofness. Virgil seems to have suffered bad health throughout his life and in some ways lived the life of an invalid. According to the Catalepton, he began to write poetry while in the Epicurean school of Siro the Epicurean at Naples. A group of small works attributed to the youthful Virgil by the commentators survive collected under the title Appendix Vergiliana, but are considered spurious by scholars.
One, the Catalepton, consists of fourteen short poems, some of which may be Virgil's, another, a short narrative poem titled the Culex, was attributed to Virgil as early as the 1st century AD. The biographical tradition asserts that Virgil began the hexameter Eclogues in 42 BC and it is thought that the collection was published around 39–38 BC, although this is controversial; the Eclogues are a group of ten poems modeled on the bucolic hexameter poetry of the Hellenistic poet Theocritus. After his victory in the Battle of Philippi in 42 BC, fought against the army led by the assassins of Julius Caesar, Octavian tried to pay off his veterans with land expropriated from towns in northern Italy including, according to the traditi
Gold is a chemical element with symbol Au and atomic number 79, making it one of the higher atomic number elements that occur naturally. In its purest form, it is a bright reddish yellow, soft and ductile metal. Chemically, gold is a group 11 element, it is solid under standard conditions. Gold occurs in free elemental form, as nuggets or grains, in rocks, in veins, in alluvial deposits, it occurs in a solid solution series with the native element silver and naturally alloyed with copper and palladium. Less it occurs in minerals as gold compounds with tellurium. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating.
Gold dissolves in mercury, forming amalgam alloys. A rare element, gold is a precious metal, used for coinage and other arts throughout recorded history. In the past, a gold standard was implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, the world gold standard was abandoned for a fiat currency system after 1971. A total of 186,700 tonnes of gold exists above ground, as of 2015; the world consumption of new gold produced is about 50% in jewelry, 40% in investments, 10% in industry. Gold's high malleability, resistance to corrosion and most other chemical reactions, conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices. Gold is used in infrared shielding, colored-glass production, gold leafing, tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine; as of 2017, the world's largest gold producer by far was China with 440 tonnes per year.
Gold is the most malleable of all metals. It can be drawn into a monoatomic wire, stretched about twice before it breaks; such nanowires distort via formation and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into a sheet of 1 square meter, an avoirdupois ounce into 300 square feet. Gold leaf can be beaten thin enough to become semi-transparent; the transmitted light appears greenish blue, because gold reflects yellow and red. Such semi-transparent sheets strongly reflect infrared light, making them useful as infrared shields in visors of heat-resistant suits, in sun-visors for spacesuits. Gold is a good conductor of electricity. Gold has a density of 19.3 g/cm3 identical to that of tungsten at 19.25 g/cm3. By comparison, the density of lead is 11.34 g/cm3, that of the densest element, osmium, is 22.588±0.015 g/cm3. Whereas most metals are gray or silvery white, gold is reddish-yellow; this color is determined by the frequency of plasma oscillations among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms.
Similar effects impart a golden hue to metallic caesium. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, both may be used to produce police and other badges. White gold alloys can be made with nickel. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with iron, purple gold can be made by alloying with aluminium. Less addition of manganese, aluminium and other elements can produce more unusual colors of gold for various applications. Colloidal gold, used by electron-microscopists, is red. Gold has only one stable isotope, 197Au, its only occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes have been synthesized, ranging in atomic mass from 169 to 205.
The most stable of these is 195Au with a half-life of 186.1 days. The least stable is 171Au. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission, α decay, β+ decay; the exceptions are 195Au, which decays by electron capture, 196Au, which decays most by electron capture with a minor β− decay path. All of gold's radioisotopes with atomic masses above 197 decay by β− decay. At least 32 nuclear isomers have been characterized, ranging in atomic mass from 170 to 200. Within that range, only 178Au, 180Au, 181Au, 182Au, 188Au do not have isomers. Gold's most stable isomer is 198m2Au with a half-life of 2.27 days. Gold's least stable isomer is 177m2Au with a half-life of only 7 ns. 184m1Au has three decay paths: β+ decay, isomeric
Noel Joseph Terence Montgomery Needham was a British biochemist and sinologist known for his scientific research and writing on the history of Chinese science and technology. He was elected a fellow of the Royal Society in 1941, a fellow of the British Academy in 1971. In 1992, Queen Elizabeth II conferred on him the Companionship of Honour, the Royal Society noted he was the only living person to hold these three titles. Needham was the only child of a London family, his father was a doctor, his mother, Alicia Adelaïde, née Montgomery, was a music composer from Oldcastle, Co. Meath, Ireland. Needham was educated at Oundle School before attending Gonville and Caius College, where he graduated BA in 1921, MA in January 1925, DPhil in October 1925, he had intended to study medicine, but came under the influence of Frederick Hopkins, resulting in his switch to biochemistry. After graduation, he was elected to a fellowship at Gonville and Caius College and worked in Hopkins' laboratory at the University Department of Biochemistry, specialising in embryology and morphogenesis.
His three-volume work Chemical Embryology, published in 1931, includes a history of embryology from Egyptian times up to the early 19th century, including quotations in most European languages. His Terry Lecture of 1936 was published by Cambridge University Press in association with Yale University Press under the title of Order and Life. In 1939 he produced a massive work on morphogenesis that a Harvard reviewer claimed "will go down in the history of science as Joseph Needham's magnum opus," little knowing what would come later. Although his career as biochemist and an academic was well established, his career developed in unanticipated directions during and after World War II. Three Chinese scientists came to Cambridge for graduate study in 1937: Lu Gwei-djen, Wang Ying-lai and Shen Shih-Chang. Lu, daughter of a Nanjing pharmacist, taught Needham Chinese, igniting his interest in China's ancient technological and scientific past, he pursued, mastered, the study of Classical Chinese with Gustav Haloun.
Under the Royal Society's direction, Needham was the director of the Sino-British Science Co-operation Office in Chongqing from 1942 to 1946. During this time he made several long journeys through war-torn China and many smaller ones, visiting scientific and educational establishments and obtaining for them much needed supplies, his longest trip in late 1943 ended in far west in Gansu at the caves in Dunhuang at the end of the Great Wall where the earliest dated printed book - a copy of the Diamond Sutra - was found. The other long trip reached Fuzhou on the east coast, returning across the Xiang River just two days before the Japanese blew up the bridge at Hengyang and cut off that part of China. In 1944 he visited Yunnan in an attempt to reach the Burmese border. Everywhere he went he purchased and was given old historical and scientific books which he shipped back to Britain through diplomatic channels, they were to form the foundation of his research. He got to know Zhou Enlai and met numerous Chinese scholars, including the painter Wu Zuoren, the meteorologist Zhu Kezhen, who sent crates of books to him in Cambridge, including 2,000 volumes of the Gujin Tushu Jicheng encyclopaedia, a comprehensive record of China's past.
On his return to Europe, he was asked by Julian Huxley to become the first head of the Natural Sciences Section of UNESCO in Paris, France. In fact it was Needham who insisted that science should be included in the organisation's mandate at an earlier planning meeting. After two years in which the suspicions of the Americans over scientific co-operation with communists intensified, Needham resigned in 1948 and returned to Gonville and Caius College, where he resumed his fellowship and his rooms, which were soon filled with his books, he devoted his energy to the history of Chinese science until his retirement in 1990 though he continued to teach some biochemistry until 1966. Needham's reputation recovered from the Korean affair such that by 1959 he was elected as president of the fellows of Caius College and in 1965 he became Master of the College, a post which he held until he was 76. In 1948, Needham proposed a project to the Cambridge University Press for a book on Science and Civilisation in China.
Within weeks of being accepted, the project had grown to seven volumes, it has expanded since. His initial collaborator was the historian Wang Ling, whom he had met in Lizhuang and obtained a position for at Trinity; the first years were devoted to compiling a list of every mechanical invention and abstract idea, made and conceived in China. These included cast iron, the ploughshare, the stirrup, printing, the magnetic compass and clockwork escapements, most of which were thought at the time to be western inventions; the first volume appeared in 1954. The publication received widespread acclaim, which increased to the lyrical as further volumes appeared, he wrote fifteen volumes himself, the regular production of further volumes continued after his death in 1995. Volume III was divided, so that 27 volumes have now been published. Successive volumes are published as they are completed, which means that they do not appear in the order contemplated in the project's prospectus. Needham's final organising schema was: Vol. I.
Introductory Orientations Vol. II. History of Scientific Thought Vol. III. Mathematics and the Sciences of the Heavens and Earth Vol. IV. Physics and Physical Technology Vol. V. Chemistry and Chemical Technology Vol. VI. Biology and Biological Technology Vol. VII; the Social Backgr
X-ray fluorescence is the emission of characteristic "secondary" X-rays from a material, excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is used for elemental analysis and chemical analysis in the investigation of metals, glass and building materials, for research in geochemistry, forensic science and art objects such as paintings and murals; when materials are exposed to short-wavelength X-rays or to gamma rays, ionization of their component atoms may take place. Ionization consists of the ejection of one or more electrons from the atom, may occur if the atom is exposed to radiation with an energy greater than its ionization energy. X-rays and gamma rays can be energetic enough to expel held electrons from the inner orbitals of the atom; the removal of an electron in this way makes the electronic structure of the atom unstable, electrons in higher orbitals "fall" into the lower orbital to fill the hole left behind. In falling, energy is released in the form of a photon, the energy of, equal to the energy difference of the two orbitals involved.
Thus, the material emits radiation. The term fluorescence is applied to phenomena in which the absorption of radiation of a specific energy results in the re-emission of radiation of a different energy; each element has electronic orbitals of characteristic energy. Following removal of an inner electron by an energetic photon provided by a primary radiation source, an electron from an outer shell drops into its place. There are a limited number of ways in which this can happen, as shown in Figure 1; the main transitions are given names: an L→K transition is traditionally called Kα, an M→K transition is called Kβ, an M→L transition is called Lα, so on. Each of these transitions yields a fluorescent photon with a characteristic energy equal to the difference in energy of the initial and final orbital; the wavelength of this fluorescent radiation can be calculated from Planck's Law: λ = h c E The fluorescent radiation can be analysed either by sorting the energies of the photons or by separating the wavelengths of the radiation.
Once sorted, the intensity of each characteristic radiation is directly related to the amount of each element in the material. This is the basis of a powerful technique in analytical chemistry. Figure 2 shows the typical form of the sharp fluorescent spectral lines obtained in the wavelength-dispersive method. In order to excite the atoms, a source of radiation is required, with sufficient energy to expel held inner electrons. Conventional X-ray generators are most used, because their output can be "tuned" for the application, because higher power can be deployed relative to other techniques. However, gamma ray sources can be used without the need for an elaborate power supply, allowing an easier use in small portable instruments; when the energy source is a synchrotron or the X-rays are focused by an optic like a polycapillary, the X-ray beam can be small and intense. As a result, atomic information on the sub-micrometre scale can be obtained. X-ray generators in the range 20–60 kV are used, which allow excitation of a broad range of atoms.
The continuous spectrum consists of "bremsstrahlung" radiation: radiation produced when high-energy electrons passing through the tube are progressively decelerated by the material of the tube anode. A typical tube output spectrum is shown in Figure 3. In energy dispersive analysis, the fluorescent X-rays emitted by the material sample are directed into a solid-state detector which produces a "continuous" distribution of pulses, the voltages of which are proportional to the incoming photon energies; this signal is processed by a multichannel analyser which produces an accumulating digital spectrum that can be processed to obtain analytical data. In wavelength dispersive analysis, the fluorescent X-rays emitted by the material sample are directed into a diffraction grating monochromator; the diffraction grating used is a single crystal. By varying the angle of incidence and take-off on the crystal, a single X-ray wavelength can be selected; the wavelength obtained is given by Bragg's law: n ⋅ λ = 2 d ⋅ sin where d is the spacing of atomic layers parallel to the crystal surface.
In energy dispersive analysis and detection are a single operation, as mentioned above. Proportional counters or various types of solid-state detectors are used, they all share the same detection principle: An incoming X-ray photon ionises a large number of detector atoms with the amount of charge produced being proportional to the energy of the incoming photon. The charge is collected and the process repeats itself for the next photon. Detector speed is critical, as all charge carriers measured have to come from the same photon to measure the photon energy correctly; the spectrum is built up by dividing the energy spectrum into discrete bins and counting the number of pulses registered within each energy bin. EDXRF detector types vary in resolution and the means of cooling
Atlantis is a fictional island mentioned within an allegory on the hubris of nations in Plato's works Timaeus and Critias, where it represents the antagonist naval power that besieges "Ancient Athens", the pseudo-historic embodiment of Plato's ideal state in The Republic. In the story, Athens repels the Atlantean attack unlike any other nation of the known world giving testament to the superiority of Plato's concept of a state; the story concludes with Atlantis falling out of favor with the deities and submerging into the Atlantic Ocean. Despite its minor importance in Plato's work, the Atlantis story has had a considerable impact on literature; the allegorical aspect of Atlantis was taken up in utopian works of several Renaissance writers, such as Francis Bacon's New Atlantis and Thomas More's Utopia. On the other hand, nineteenth-century amateur scholars misinterpreted Plato's narrative as historical tradition, most notably in Ignatius L. Donnelly's Atlantis: The Antediluvian World. Plato's vague indications of the time of the events—more than 9,000 years before his time—and the alleged location of Atlantis—"beyond the Pillars of Hercules"—has led to much pseudoscientific speculation.
As a consequence, Atlantis has become a byword for any and all supposed advanced prehistoric lost civilizations and continues to inspire contemporary fiction, from comic books to films. While present-day philologists and classicists agree on the story's fictional character, there is still debate on what served as its inspiration; as for instance with the story of Gyges, Plato is known to have borrowed some of his allegories and metaphors from older traditions. This led a number of scholars to investigate possible inspiration of Atlantis from Egyptian records of the Thera eruption, the Sea Peoples invasion, or the Trojan War. Others have rejected this chain of tradition as implausible and insist that Plato created an fictional nation as his example, drawing loose inspiration from contemporary events such as the failed Athenian invasion of Sicily in 415–413 BC or the destruction of Helike in 373 BC; the only primary sources for Atlantis are Plato's dialogues Critias. The dialogues claim to quote Solon, who visited Egypt between 590 and 580 BC.
Written in 360 BC, Plato introduced Atlantis in Timaeus: For it is related in our records how once upon a time your State stayed the course of a mighty host, starting from a distant point in the Atlantic ocean, was insolently advancing to attack the whole of Europe, Asia to boot. For the ocean there was at that time navigable. For all that we have here, lying within the mouth of which we speak, is evidently a haven having a narrow entrance. Now in this island of Atlantis there existed a confederation of kings, of great and marvelous power, which held sway over all the island, over many other islands and parts of the continent; the four people appearing in those two dialogues are the politicians Critias and Hermocrates as well as the philosophers Socrates and Timaeus of Locri, although only Critias speaks of Atlantis. In his works Plato makes extensive use of the Socratic method in order to discuss contrary positions within the context of a supposition; the Timaeus begins with an introduction, followed by an account of the creations and structure of the universe and ancient civilizations.
In the introduction, Socrates muses about the perfect society, described in Plato's Republic, wonders if he and his guests might recollect a story which exemplifies such a society. Critias mentions a tale he considered to be historical, that would make the perfect example, he follows by describing Atlantis as is recorded in the Critias. In his account, ancient Athens seems to represent the "perfect society" and Atlantis its opponent, representing the antithesis of the "perfect" traits described in the Republic. According to Critias, the Hellenic deities of old divided the land so that each deity might have their own lot; the island was larger than Ancient Libya and Asia Minor combined, but it was sunk by an earthquake and became an impassable mud shoal, inhibiting travel to any part of the ocean. Plato asserted that the Egyptians described Atlantis as an island consisting of mountains in the northern portions and along the shore and encompassing a great plain in an oblong shape in the south "extending in one direction three thousand stadia, but across the center inland it was two thousand stadia."
Fifty stadia from the coast was a mountain, low on all sides... broke it off all round about... the central island itself was five stades in diameter. In Plato's metaphorical tale, Poseidon fell in love with Cleito, the daughter of Evenor and Leucippe, who bore him five pairs of male twins; the eldest of these, was made rightful king of the entire island and the ocean, was given the mountain of his birth and the surrounding area as his fiefdom. Atlas's twin Gadeirus, or Eumelus in Greek, was given the extremity of the island to
Sicily is the largest island in the Mediterranean Sea and one of the 20 regions of Italy. It is one of the five Italian autonomous regions, in Southern Italy along with surrounding minor islands referred to as Regione Siciliana. Sicily is located in the central Mediterranean Sea, south of the Italian Peninsula, from which it is separated by the narrow Strait of Messina, its most prominent landmark is Mount Etna, the tallest active volcano in Europe, one of the most active in the world 3,329 m high. The island has a typical Mediterranean climate; the earliest archaeological evidence of human activity on the island dates from as early as 12,000 BC. By around 750 BC, Sicily had three Phoenician and a dozen Greek colonies and, for the next 600 years, it was the site of the Sicilian Wars and the Punic Wars. After the fall of the Roman Empire in the 5th century AD, Sicily was ruled during the Early Middle Ages by the Vandals, the Ostrogoths, the Byzantine Empire, the Emirate of Sicily; the Norman conquest of southern Italy led to the creation of the Kingdom of Sicily, subsequently ruled by the Hohenstaufen, the Capetian House of Anjou and the House of Habsburg.
It was unified under the House of Bourbon with the Kingdom of Naples as the Kingdom of the Two Sicilies. It became part of Italy in 1860 following the Expedition of the Thousand, a revolt led by Giuseppe Garibaldi during the Italian unification, a plebiscite. Sicily was given special status as an autonomous region on 15th May 1946, 18 days before the Italian constitutional referendum of 1946. Albeit, much of the autonomy still remains unapplied financial autonomy, because the autonomy-activating laws have been deferred to be approved by the parithetic committee, since 1946. Sicily has a rich and unique culture with regard to the arts, literature and architecture, it is home to important archaeological and ancient sites, such as the Necropolis of Pantalica, the Valley of the Temples and Selinunte. Sicily has a triangular shape, earning it the name Trinacria. To the east, it is separated from the Italian mainland by the Strait of Messina, about 3 km wide in the north, about 16 km wide in the southern part.
The northern and southern coasts are each about 280 km long measured as a straight line, while the eastern coast measures around 180 km. The total area of the island is 25,711 km2, while the Autonomous Region of Sicily has an area of 27,708 km2; the terrain of inland Sicily is hilly and is intensively cultivated wherever possible. Along the northern coast, the mountain ranges of Madonie, 2,000 m, Nebrodi, 1,800 m, Peloritani, 1,300 m, are an extension of the mainland Apennines; the cone of Mount Etna dominates the eastern coast. In the southeast lie the lower Hyblaean Mountains, 1,000 m; the mines of the Enna and Caltanissetta districts were part of a leading sulphur-producing area throughout the 19th century, but have declined since the 1950s. Sicily and its surrounding small islands have some active volcanoes. Mount Etna is the largest active volcano in Europe and still casts black ash over the island with its ever-present eruptions, it stands 3,329 metres high, though this varies with summit eruptions.
It is the highest mountain in Italy south of the Alps. Etna covers an area of 1,190 km2 with a basal circumference of 140 km; this makes it by far the largest of the three active volcanoes in Italy, being about two and a half times the height of the next largest, Mount Vesuvius. In Greek mythology, the deadly monster Typhon was trapped under the mountain by Zeus, the god of the sky. Mount Etna is regarded as a cultural symbol and icon of Sicily; the Aeolian Islands in the Tyrrhenian Sea, to the northeast of mainland Sicily form a volcanic complex, include Stromboli. The three volcanoes of Vulcano and Lipari are currently active, although the latter is dormant. Off the southern coast of Sicily, the underwater volcano of Ferdinandea, part of the larger Empedocles volcano, last erupted in 1831, it is located between the island of Pantelleria. The autonomous region includes several neighbouring islands: the Aegadian Islands, the Aeolian Islands and Lampedusa; the island is drained by several rivers, most of which flow through the central area and enter the sea at the south of the island.
The Salso flows through parts of Enna and Caltanissetta before entering the Mediterranean Sea at the port of Licata. To the east, the Alcantara flows through the province of Messina and enters the sea at Giardini Naxos, the Simeto, which flows into the Ionian Sea south of Catania. Other important rivers on the island are the Platani in the southwest. Sicily has a typical Mediterranean climate with mild and wet winters and hot, dry summers with changeable intermediate seasons. On the coasts the south-western, the climate is affected by the African currents and summers can be scorching. Sicily is seen as an island of warm winters but above all along the Tyrrhenian coast and in the inland areas, winters can be cold, with typical continental climate. Snow falls in abundance above 900–1000 metres, but stronger cold waves can carry it in the hills and in coastal cities on the northern coast of the island; the interi
The dupondius was a brass coin used during the Roman Empire and Roman Republic valued at 2 asses. The dupondius was introduced during the Roman Republic as a large bronze cast coin, although at introduction it weighed less than 2 pounds; the initial coins featured the bust of Roma on a six-spoked wheel on the reverse. With the coinage reform of Augustus in about 23 BC, the sestertius and dupondius were produced in a golden colored copper-alloy called orichalcum by the Romans and numismatists, Latin brass by us, while lower denominations were produced out of reddish copper. However, some dupondii were made from copper under Augustus, while under Nero some aes were made from both orichalcum and copper, instead of only copper for aes coined until then. Therefore, the latter can only be distinguished from dupondii by their smaller size instead of by the appearance of the metal; the dupondius was further distinguished from the sized as with the addition of a radiate crown to the bust of the emperor in 66 AD during the reign of Nero.
Using a radiate crown to indicate double value was markedly used on the antoninianus introduced by Caracalla and the double sestertius. Since dupondii minted prior to and during the reign of Nero, under rulers, lack the radiate crown, it is hard to distinguish between the as and the dupondius due to heavy patina which obscures the coin's original color. An rare dupondius from the reign of Marcus Aurelius, dated to 154 or 155 and in excellent condition, was discovered in 2007 at the archeological site in Draper's Gardens, London. Roman currency