Neon

For other uses, see Neon (disambiguation).
General Name, Symbol, Number neon, Ne, 10 Chemical series noble gases Group, Period, Block 18, 2, p Appearance colorless
Atomic mass 20.1797(6) g/mol Electron configuration 1s2 2s2 2p6 Electrons per shell 2, 8 Physical properties Phase gas Density (0 °C, 101.325 kPa)
0.9002 g/L Melting point 24.56 K
(-248.59 °C, -415.46 °F) Boiling point 27.07 K
(-246.08 °C, -410.94 °F) Heat of fusion 0.335 kJ/mol Heat of vaporization 1.71 kJ/mol Heat capacity (25 °C) 20.786 J/(mol·K) Atomic properties Crystal structure cubic face centered Oxidation states no data Ionization energies
(more) 1st: 2080.7 kJ/mol 2nd: 3952.3 kJ/mol 3rd: 6122 kJ/mol Atomic radius (calc.) 38 pm Covalent radius 69 pm Van der Waals radius 154 pm Miscellaneous Magnetic ordering nonmagnetic Thermal conductivity (300 K) 49.1 mW/(m·K) Speed of sound (gas, 0 °C) 435 m/s CAS registry number 7440-01-9 Notable isotopes References

Neon is the chemical element in the periodic table that has the symbol Ne and atomic number 10. A colorless nearly inert noble gas, neon gives a distinct reddish glow when used in vacuum discharge tubes and neon lamps and is found in air in trace amounts.

Notable characteristics

Neon is the second-lightest noble gas, glows reddish-orange in a vacuum discharge tube and has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen (on a per unit volume basis). In most applications it is a less expensive refrigerant than helium. Neon has the most intense discharge at normal voltages and currents of all the rare gases.

Applications

Neon is often used in signs

The reddish-orange color that neon emits in neon lights is widely used to make advertising signs. The word "neon" is also used generically for these types of lights when in reality many other gases are used to produce different colors of light. Other uses:

History

Neon (Greek neos meaning "new") was discovered by Scottish chemist William Ramsay and English chemist Morris Travers in 1898.

Occurrence

Neon is usually found in the form of a gas with molecules consisting of a single neon atom. Neon is a rare gas that is found in the Earth's atmosphere at 1 part in 65,000 and is produced by supercooling air and fractionally distilling it from the resulting cryogenic liquid. Neon, like water vapor, is lighter than air; unlike water vapor, which condenses into a liquid below the stratosphere and is thus trapped in Earth's atmosphere, neon may slowly leak out into space, which explains its scarcity on Earth. Argon, in contrast, is heavier than air and so remains within Earth's atmosphere.

Compounds

The ions, Ne+, (NeAr)+, (NeH)+, and (HeNe+), have been observed from optical and mass spectrometric research. In addition, neon forms an unstable hydrate.

Isotopes

Neon has three stable isotopes: 20Ne (90.48%), 21Ne (0.27%) and 22Ne (9.25%). 21Ne and 22Ne are nucleogenic and their variations are well understood. In contrast, 20Ne is not known to be nucleogenic and the causes of its variation in the Earth have been hotly debated. The principal nuclear reactions which generate neon isotopes are neutron emission, alpha decay reactions on 24Mg and 25Mg, which produce 21Ne and 22Ne, respectively. The alpha particles are derived from uranium-series decay chains, while the neutrons are mostly produced by secondary reactions from alpha particles. The net result yields a trend towards lower 20Ne/22Ne and higher 21Ne/22Ne ratios observed in uranium-rich rocks such as granites. Isotopic analysis of exposed terrestrial rocks has demonstrated the cosmogenic production of 21Ne. This isotope is generated by spallation reactions on magnesium, sodium, silicon, and aluminium. By analyzing all three isotopes, the cosmogenic component can be resolved from magmatic neon and nucleogenic neon. This suggests that neon will be a useful tool in determining cosmic exposure ages of surficial rocks and meteorites.

Similar to xenon, neon content observed in samples of volcanic gases are enriched in 20Ne, as well as nucleogenic 21Ne, relative to 22Ne content. The neon isotopic content of these mantle-derived samples represent a non-atmospheric source of neon. The 20Ne-enriched components are attributed to exotic primordial rare gas components in the Earth, possibly representing solar neon. Elevated 20Ne abundances are also found in diamonds, further suggesting a solar neon reservoir in the Earth.

References


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Elevated 20Ne abundances are also found in diamonds, further suggesting a solar neon reservoir in the Earth. This further opened up some of the area to prospectors. The 20Ne-enriched components are attributed to exotic primordial rare gas components in the Earth, possibly representing solar neon. In 1885 a mining expeditionary party under the Romanian adventurer Julius Popper landed in southern Patagonia in search of gold, which they found after travelling southwards towards the lands of Tierra del Fuego. The neon isotopic content of these mantle-derived samples represent a non-atmospheric source of neon. Captain George Chaworth Musters in 1869 wandered in company with a band of Tehuelches through the whole length of the country from the strait to the Manzaneros in the north-west, and collected a great deal of information about the people and their mode of life. Similar to xenon, neon content observed in samples of volcanic gases are enriched in 20Ne, as well as nucleogenic 21Ne, relative to 22Ne content. The expeditions of HMS Adventure (1826–1830) and HMS Beagle (1832–1836) under Philip Parker King and Robert FitzRoy respectively were of first-rate importance, the latter especially from the participation of Charles Darwin; however nothing was observed of the interior of the country except for 200 miles (320 km) of the course of the Santa Cruz.

This suggests that neon will be a useful tool in determining cosmic exposure ages of surficial rocks and meteorites. Thomas Falkner, a Jesuit who resided near forty years in those parts, published his Description of Patagonia (Hereford, 1774); Francesco Viedma founded El Carmen, and Antonio advanced inland to the Andes (1782); and Basilio Villarino ascended the Rio Negro (1782). By analyzing all three isotopes, the cosmogenic component can be resolved from magmatic neon and nucleogenic neon. In the second half of the 18th century knowledge of Patagonia was further augmented by the voyages of the previously-mentioned John Byron (1764–1765), Samuel Wallis (1766, in the same HMS Dolphin which Byron had earlier sailed in) and Louis Antoine de Bougainville (1766). This isotope is generated by spallation reactions on magnesium, sodium, silicon, and aluminium. Interest soon subsided, although awareness of and belief in the myth persisted in some quarters even up into the 20th century1. Isotopic analysis of exposed terrestrial rocks has demonstrated the cosmogenic production of 21Ne. In this publication, drawn from their official logs, it became clear that the people Byron's expedition had encountered were no taller than 6 foot 6 inches, tall perhaps but by no means giants.

The net result yields a trend towards lower 20Ne/22Ne and higher 21Ne/22Ne ratios observed in uranium-rich rocks such as granites. In 1773 John Hawkesworth published on behalf of the Admiralty a compendium of noted English southern-hemisphere explorers' journals, including that of James Cook and John Byron. The alpha particles are derived from uranium-series decay chains, while the neutrons are mostly produced by secondary reactions from alpha particles. However, the Patagonian giant frenzy was to die down substantially only a few years later, when some more sober and analytical accounts were published. The principal nuclear reactions which generate neon isotopes are neutron emission, alpha decay reactions on 24Mg and 25Mg, which produce 21Ne and 22Ne, respectively. Byron and crew had spent some time along the coast, and the publication (Voyage Round the World in His Majesty’s Ship the Dolphin) seemed to give proof positive of their existence; the publication became an overnight best-seller, thousands of extra copies were to be sold to a willing public, and other prior accounts of the region were hastily re-published (even those in which giant-like folk were not mentioned at all). In contrast, 20Ne is not known to be nucleogenic and the causes of its variation in the Earth have been hotly debated. The concept and general belief persisted for a further 250 years, and was to be sensationally re-ignited in 1767 when an "official" (but anonymous) account was published of Commodore John Byron's recent voyage of global circumnavigation in HMS Dolphin.

21Ne and 22Ne are nucleogenic and their variations are well understood. By 1611 the Patagonian god Setebos (Settaboth in Pigafetta) was familiar to the hearers of the Tempest. Neon has three stable isotopes: 20Ne (90.48%), 21Ne (0.27%) and 22Ne (9.25%). Early charts of the New World sometimes added the legend regio gigantum ("region of the giants") to the Patagonian area. In addition, neon forms an unstable hydrate. This supposed race of Patagonian giants or Patagones entered into the common European perception of this little-known and distant area, to be further fuelled by subsequent reports of other expeditions and famous-name travellers like Sir Francis Drake, which seemed to confirm these accounts. The ions, Ne+, (NeAr)+, (NeH)+, and (HeNe+), have been observed from optical and mass spectrometric research. The main interest in the region sparked by Pigafetta's account came from his reports of their meeting with the local inhabitants, who they claimed to measure some nine to twelve feet in height —"...so tall that we reached only to his waist"—, and hence the later idea that Patagonia meant "big feet".

Argon, in contrast, is heavier than air and so remains within Earth's atmosphere. However, this etymology is questionable. Neon, like water vapor, is lighter than air; unlike water vapor, which condenses into a liquid below the stratosphere and is thus trapped in Earth's atmosphere, neon may slowly leak out into space, which explains its scarcity on Earth. Although Pigafetta's account does not describe how this name came about, subsequent popular interpretations gave credence to a derivation meaning 'land of the big feet'. Neon is a rare gas that is found in the Earth's atmosphere at 1 part in 65,000 and is produced by supercooling air and fractionally distilling it from the resulting cryogenic liquid. According to Antonio Pigafetta, one of the Magellan expedition's few survivors and its published chronicler, Magellan bestowed the name "Patagão" (or Patagoni) on the inhabitants they encountered there, and the name "Patagonia" for the region. Neon is usually found in the form of a gas with molecules consisting of a single neon atom. The district in the neighbourhood of Puerto Deseado, explored by John Davis about the same period, was taken possession of by Sir John Narborough in the name of King Charles II of England in 1669.

Neon (Greek neos meaning "new") was discovered by Scottish chemist William Ramsay and English chemist Morris Travers in 1898. The settlement which he founded at Nombre de Dios and San Felipe were neglected by the Spanish government, and the latter was in such a miserable state when Thomas Cavendish visited it in 1587 that he called it Port Famine. Other uses:. Alonzo de Camargo (1539), Juan Ladrilleros (1557) and Hurtado de Mendoza (1558) helped to make known the western coasts, and Sir Francis Drake's voyage in 1577 down the eastern coast through the strait and northward by Chile and Peru was memorable for several reasons; but the geography of Patagonia owes more to Pedro Sarmiento de Gamboa (1579–1580), who, devoting himself especially to the south-west region, made careful and accurate surveys. The word "neon" is also used generically for these types of lights when in reality many other gases are used to produce different colors of light. Pedro de Mendoza, on whom the country was next bestowed, lived to found Buenos Aires, but not to carry his explorations to the south. The reddish-orange color that neon emits in neon lights is widely used to make advertising signs. Rodrigo de Isla, despatched inland in 1535 from San Matias by Alcazava Sotomayor (on whom western Patagonia had been conferred by the king of Spain), was the first European to traverse the great Patagonian plain, and, but for the mutiny of his men, he may have been able to strike across the Andes to reach the Chilean side.

Neon has the most intense discharge at normal voltages and currents of all the rare gases. However, it is also possible that earlier navigators such as Amerigo Vespucci had reached the area (his own account of 1502 has it that he reached its latitudes), however his failure to accurately describe the main geographical features of the region such as the Rio de la Plata casts some doubt on whether he really did so. In most applications it is a less expensive refrigerant than helium. The region of Patagonia was to be first noted in European accounts in 1520 by the expedition of Ferdinand Magellan, who on his passage along the coast named many of the more striking features -- Gulf of San Matias, Cape of 11,000 Virgins (now simply Cape Virgenes), and others. Neon is the second-lightest noble gas, glows reddish-orange in a vacuum discharge tube and has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen (on a per unit volume basis). The indigenous peoples of the region included the Tehuelches, whose numbers and society were reduced to near extinction not long after the first contacts with Europeans. . The region seems to have been inhabited continuously since that time, by various cultures and alternating waves of migration, the details of which are as yet poorly understood.

A colorless nearly inert noble gas, neon gives a distinct reddish glow when used in vacuum discharge tubes and neon lamps and is found in air in trace amounts. Human habitation of the region dates back thousands of years, with some early archaeological findings in the southern part of the area dated to the 10th millennium BCE, although later dates of around the 8th millennium BCE are more securely recognised. Neon is the chemical element in the periodic table that has the symbol Ne and atomic number 10. Of the many kinds of water-fowl it is enough to mention the flamingo, the upland goose, and in the strait the remarkable steamer duck. Los Alamos National Laboratory – Neon. The carancho or carrion-hawk (Polyborus tharus) is one of the characteristic objects of a Patagonian landscape; the presence of long-tailed green parakeets (Conurus cyanolysius) as far south as the shores of the strait attracted the attention of the earlier navigators; and hummingbirds may be seen flying amidst the falling snow. Liquefied neon is commercially used as an economical cryogenic refrigerant. Bird-life is often wonderfully abundant.

Neon and helium are used to make a type of gas laser. The guanaco roam in herds over the country and form with the rhea (Rhea americana, and more rarely Rhea darwinii) the chief means of subsistence for the natives, who hunt them on horseback with dogs and bolas. television tubes. The guanaco, the puma, the zorro or Brazilian fox (Canis azarae), the zorrino or Mephitis patagonica (a kind of skunk), and the tuco-tuco or Ctenomys niagellanicus (a rodent) are the most characteristic mammals of the Patagonian plains. wave meter tubes. At Punta Arenas it is 560 mm (22 inches). lightning arrestors. The prevailing winds are westerly, and the westward slope has a much heavier precipitation than the eastern; thus at Puerto Montt the mean annual precipitation is 2.46 m (97 inches), but at Bahia Blanca it is 480 mm (19 inches).

high-voltage indicators. At Punta Arenas, in the extreme south, the mean temperature is 6 °C (43 °F) and the average extremes 24.5 °C (76 °F) and −2 °C (28 °F). vacuum tubes. the mean annual temperature is 11 °C (52 °F) and the average extremes 25.5 °C (78 °F) and −1.5 °C (29.5 °F), whereas at Bahia Blanca near the Atlantic coast and just outside the northern confines of Patagonia the annual temperature is 15 °C (59 °F) and the range much greater. At Puerto Montt, on the inlet behind Chiloé Island. The east slope is warmer than the west, especially in summer, as a branch of the southern equatorial current reaches its shores, whereas the west coast is washed by a cold current.

The climate is less severe than was supposed by early travellers. It consist of the 47,992 km² of the Isla Grande de Tierra del Fuego, and several minor islands. Tierra del Fuego is an archipelago at the southernmost tip of Patagonia, divided between Argentina and Chile. But the colonization of the western (Chilean) coast has generally failed, principally owing to the adverse climatic conditions of the Cordillera in those latitudes.

Its population in 1911 numbered about 4000. Owing to the produce of the cattle farms established there, the working of coal in the neighbourhood, and the export of timber from the surrounding forests, the town of Punta Arenas is in a flourishing condition. Puerto Gallegos itself is an important business center, which bids fair to rival the Chilean colony of Punta Arenas, on the Straits of Magellan. But the present cattle region par excellence of Patagonia is the department of Rio Gallegos, the farms extending from the Atlantic to the Cordillera.

In Santa Cruz bay an important trade centre has been established. The Rio Santa Cruz, originally explored by Captain Robert FitzRoy and Charles Darwin during the Voyage of the Beagle, is an important artery of communication between the regions bordering upon the Cordillera and the Atlantic. In the Cretaceous hills which flank the Cordillera important lignite beds and deposits of mineral oils have been discovered. The valleys of the Rio Chico throughout their whole extent, as well as those of Lake Shehuen, afford excellent grazing, and around Lakes Belgrano, Burmeister and Rio Mayer and San Martin there are spots suitable for cultivation.

San Julian on Puerto San Julian, where Ferdinand Magellan wintered, was the centre of a cattle farming colony, and colonists have pushed into the interior up the valley of a now extinct river which in comparatively recent times carried down to Puerto San Julian the waters of Lakes Volcan, Beigrano, Azara, Nansen, and some other lakes which now drain into the river Mayer and so into Lake San Martin. Lake Buenos Aires, the largest lake in Patagonia, measuring 120 kilometers (75 miles) in length, poured its waters into the Atlantic even in post-Glacial times by means of the river Deseado; and it is so depicted on the maps of the 17th and 18th centuries; and so too did Lake Pueyrredon, which, through the action of erosion, now empties itself westward, through the river Las Heras, into the Calen inlet of the Pacific, in 48°S. Into this inlet there flowed at the time of the conquest a voluminous river, which subsequently disappeared, but returned again to its ancient bed, owing to the river Fenix, one of its affluents, which had deviated to the west, regaining its original direction. Puerto Deseado is the outlet for the produce of the Andean region situated between Lakes Buenos Aires and Pueyrredon.

With the exception of certain valleys at Puerto Deseado (Port Desire) and in the transverse basins which occur as far south as Puerto San Julian, and which contain several cattle farms, few spots are capable of cultivation, the pastures being poor, water insufficient and salt lagoons fairly numerous. The territory of Santa Cruz is arid along the Atlantic coast and in the central portion between 46° and 50°S. miles). parallel, as far south as the dividing line with Chile, and between Point Dungeness and the watershed of the Cordillera, has an area of 243,943 km² (94,186 sq.

Santa Cruz, which stretches from the 46° to the 50°S. Every year thousands of fly fishermen flock there for the hope of catching "the big one". In addition it is one of the highest critically acclaimed group of rivers in the the world for fly fishing. Colonies have also been formed in the basin of Lakes Musters and Colhué Huapi; and on the coasts near the Atlantic, along Bahia Camarones and the Gulf of San Jorge, there are extensive farms.

The streams which form the rivers Mayo and Chalia join the tributaries of the Rio Aisen, which flows into the Pacific, watering in its course extensive and valuable districts where colonization has been initiated by Argentine settlers. At Lake Fontana there are auriferous drifts and lignite deposits which abound in fossil plants of the Cretaceous age. This region contains auriferous drifts, but these, like the auriferous deposits, veins of galena and lignite in the mountains farther west which flank the Cordillera, have not been properly investigated. Rio Pico, an affluent of the same river, receives nearly the whole of the waters of the extensive undulating plain which lies between the Rio Tecka and the Rio Senguerr to the east of the Cordillera, while the remainder are carried away by the affluents of Rio Jehua: the Cherque, Omkel, and Appeleg.

The principal affluent of the Palena, the Carrenleufu, carries off the waters of Lake General Paz, situated on the eastern slope of the Cordillera. Other rivers in this territory flow into the Pacific through breaches in the Cordillera, e.g. the upper affluents of the Futaleufú River, Palena and Rio Cisnes. The chief of these colonies is that of 16 de Octubre, formed in 1886, mainly by the inhabitants of Chubut colony, in the longitudinal valley which extends to the eastern foot of the Cordillera. Between the Chubut and the Senguerr there are vast stretches of fertile land, spreading over the Andean region to the foot of the Cordillera and the lateral ridges of the Pre-Cordillera, and filling the basins of some desiccated lakes, which have been occupied since 1885, and farms and colonies founded upon them.

The valley has been irrigated and cultivated, and produces the best wheat of the Argentine Republic. Here is the seat of the governor of the territory, and by 1895 the inhabitants of this part of the territory, composed principally of Argentines, Welsh and Italians, numbered 2585. The town was founded in 1865 by a group of colonists from Wales, assisted by the Argentine government; and its prosperity has led to the foundation of other important centres in the valley, such as Trelew and Gaiman, which is connected by railway with Puerto Madryn on Bahia Nueva. Rawson, the capital, is situated at the mouth of the river Chubut on the Atlantic (42°30'S).

Chubut territory presents the same characteristics as the Río Negro territory. miles), embracing the region between 42° and 46°S;. Chubut, covers 224,686 km² (86,751 sq. In 42°S there is a third broad transverse depression, apparently the bed of another great river, now perished, which carried to the Atlantic the waters of a portion of the eastern slope of the Andes, between 41° and 42°30;S.

To the south of the Rio Negro the Patagonian plateau is intersected by the depressions of the Gualicho and Maquinchao, which in former times directed the waters of two great rivers (now disappeared) to the gulf of San Matias, the first-named depression draining the network of the Collon Cura and the second the Nahuel Huapi lake system. In this depression are several settlements, among them Viedma, the capital of the Rio Negro territory, Pringles, General Conesa, Choele Choel and General Roca. the middle part of which is followed by the railway which runs to the settlement of Neuquen at the confluence of the rivers Limay and Neuquen. The Río Negro River runs along a wide transverse depression.

miles), extending from the Atlantic to the Cordillera of the Andes, to the north of 42°S. Río Negro covers 203,013 km² (78,383 sq. Lake Lacar is now a contributary of the Pacific, its outlet having been changed to the west, owing to a passage having been opened through the Cordillera. These regions are drained by the river Collon Cura, the principal affluent of the river Limay.

Close to these are the famous apple orchards supposed to have been planted by the Jesuits in the 17th and 18th centuries. The wide valleys occur near Rio Malleo, Lake Huechulafquen, the river Chimehuin, and Vega de Chapelco, near Lake Lacar, where are situated villages of some importance, such as Junin de los Andes and San Martin de los Andes. In the centre of the territory, also in the neighborhood of the mining districts, are the valleys of Norquin and Las Lajas, the general camp of the Argentine army in Patagonia, with excellent timber in the forest on the Andean slope. More to the west is the mining region, in great part unexplored, but containing deposits of gold, silver, copper and lignite.

Chos Malal, the capital of the territory, is situated in one of these valleys. As the Cordillera is approached the soil becomes more fertile, and suitable districts for the rearing of cattle and other agricultural purposes exist between the regions which surround the Tromen volcano and the first ridges of the Andes. The Neuquen river is not navigable, but as its waters are capable of being easily dammed in places, large stretches of land in its valley are utilized; but the lands on each side of its lower part are of little commercial value. On the upper plains of Neuquen territory thousands of cattle can be fed, and the forests around Lakes Tiaful and Nahuel-Huapi yield large quantities of valuable timber.

miles), including the triangle between the Limay River and Neuquén River, which extends southward to the northern shore of Lake Nahuel-Huapi (41°S) and northward to the Rio Colorado. Neuquén covers 94,078 km² (36,324 sq. Population = 1,740,000 (2001 census).
Land Area = 787,000 km2
Population Density = 2.21 / km2
. With the exception of the discoveries at the inlet of Ultima Esperanza, which is in close communication with the Atlantic valley of Río Gallegos, none of these remains have been discovered in the Andean regions.

The animals undoubtedly reached these localities from the east; it is not at all probable that they advanced from the north southwards across the plateau intersected at that cime by great rivers and covered by the ice-sheet. One fact, however, which apparently demonstrates with greater certainty the existence in recent times of land that is now lost, is the presence of remains of pampean mammals in Pleistocene deposits in the bay of Puerto San Julian and in Santa Cruz. There are besides, in the neighborhood of the present coast, deposits of volcanic ashes, and the ocean throws up on its shores blocks of basaltic lava, which in all probability proceed from eruptions of submerged volcanoes now extinct. From an examination of the pampean formation it is evident that in recent times the land of the province of Buenos Aires extended farther to the east, and that the advance of the sea, and the salt-water deposits left by it when it retired, forming some of the lowlands which occur on the littoral and in the interior of the pampas, are much more recent phenomena; and certain caps of shingle, derived from rocks of a different class from those of the neighboring hills, which are observed on the Atlantic coasts of the same province, and increase in quantity and size towards the south, seem to indicate that the caps of shingle which now cover such a great part of the Patagonian territory recently extended farther to the east, over land which has now disappeared beneath the sea, while other marine deposits along the same coasts became converted into bays during the subsequent advance of the sea.

They are composed of caps of shingle, with great, more or less rounded boulders, sand and volcanic ashes, precisely of the same form as occurs on the Patagonian plateau. Some of the promontories of Chiloé are still called huapi, the Araucanian equivalent for "islands"; and this may perhaps be accepted as perpetuating the recollection of the time when they actually were islands. In so far as its main characteristics are concerned, Patagonia seems to be a portion of the Antarctic continent, the permanence of which dates from very recent times, as is evidenced by the apparent recent emergence of the islets around Chiloé, and by the general character of the pampean formation. Several of the high peaks are still active volcanoes.

These ice-sheets, which scooped out the greater part of the longitudinal depressions, and appear to have rapidly retreated to the point where the glaciers now exist, did not, however, in their retirement fill up with their detritus the fjords of the Cordillera, for these are now occupied by deep lakes on the east, and on the west by the Pacific channels, some of which are as much as 250 fathoms (460 m) in depth, and soundings taken in them show that the fjords are as usual deeper in the vicinity of the mountains than to the west of the islands. In Patagonia an immense ice-sheet extended to the east of the present Atlantic coast during the first ice age, at the close of the Tertiary epoch, while, during the second glacial age in modern times, the terminal moraines have generally stopped, 30 miles (50 km) in the north and 50 miles (80 km) in the south, east of the summit of the Cordillera. Glaciers occupy the valleys of the main chain and some of the lateral ridges of the Cordillera, and descend to lakes San Martín Lake, Viedma Lake, Argentino Lake and others in the same locality, strewing them with icebergs. It would not be surprising if this latter animal were still in existence, for footprints, which may be attributed to it, have been observed on the borders of the rivers Tamangoand Pista, affluents of the Las Hefas, which run through the eastern foot-hills of the Cordillera in 47°S.

With the remains of Grypotherium have been found those of the horse (Onoshippidium), which are known only from the lower pampas mud, and of the Arciotherium, which is found, although not in abundance, in even the most modern Pleistocene deposits in the pampas of Buenos Aires. In deposits of much later date, formed when the physiognomy of the country did not differ materially from that of the present time, there have been discovered remains of pampean mammals, such as Glyptodon and Macrauchenia, and in a cave near Last Hope Inlet, a gigantic ground sloth (Grypoiherium listai), an animal which lived contemporaneously with man, and whose skin, well preserved, showed that its extermination was undoubtedly very recent. In the Tertiary marine formation a considerable number of cetaceans has been discovered. Other specimens of the interesting fauna of Patagonia, belonging to the Middle Tertiary, are the gigantic wingless birds, exceeding in size any hitherto known, and the singular mammal Pyrotherium, also of very large dimensions.

The Patagonian Myolania belongs to the Upper Chalk, having been found associated with remains of Dinosauria. This, together with the discovery of the perfect cranium of a chelonian of the genus Myolania, which may be said to be almost identical with Myolania oweni of the Pleistocene age in Queensland, forms an evident proof of the connection between the Australian and South American continents. The Upper Cretaceous and Tertiary deposits have revealed a most interesting vertebrate fauna. They are divided by Wilckensi into the following series (in ascending order):.

The Tertiary deposits are greatly varied in character, and there is considerable difference of opinion concerning the succession and correlation of the beds. Porphyritic rocks occur between the schists and the quartzites. First come Lower Cretaceous hills, raised by granite and dioritic rocks, undoubtedly of Tertiary origin, as in some cases these rocks have broken across the Tertiary beds, so rich in mammal remains; then follow, on the west, metamorphic schists of uncertain age; then quartzites appear, resting directly on the primitive granite and gneiss which form the axis of the Cordillera. The Tertiary plateau, flat on the east, gradually rising on the west, shows Upper Cretaceous caps at its base.

The geological constitution is in accordance with the orographic physiognomy. This latter depression contains the richest and most fertile land of Patagonia. There, in contact with folded Cretaceous rocks, uplifted by the Tertiary granite, erosion, caused principally by the sudden melting and retreat of the ice, aided by tectonic changes, has scooped out a deep longitudinal depression, which generally separates the plateau from the first lofty hills, the ridges generally called the pre-Cordillera, while on the west of these there is a similar longitudinal depression all along the foot of the snowy Andean Cordillera. In the central region volcanic eruptions, which have taken part in the formation of the plateau from the Tertiary period down to the present era, cover a large part with basaltic lava-caps; and in the western third more recent glacial deposits appear above the lava.

Besides these transverse depressions (some of them marking lines of ancient inter-oceanic communication), there are others which were occupied by more or less extensive lakes, such as the Yagagtoo, Musters, and Colhue Huapi, and others situated to the south of Puerto Deseado, in the centre of the country. Among the depressions by which the plateau is intersected transversely, the principal are the Gualichu, south of the Rio Negro, the Maquinchao and Valcheta (through which previously flowed the waters of lake Nahuel Huapi, which now feed the river Limay); the Senguerr, the Deseado River. Towards the Andes the shingle gives place to porphyry, granite, and basalt lavas, animal life becomes more abundant and vegetation more luxuriant, acquiring the characteristics of the flora of the western coast, and consisting principally of southern beech and conifers. In the hollows of the plains are ponds or lakes of brackish and fresh water.

The general character of the Argentine portion of Patagonia is for the most part a region of vast steppe-like plains, rising in a succession of abrupt terraces about 100 meters (330 feet) at a time, and covered with an enormous bed of shingle almost bare of vegetation. . East of the Andes the Argentine portion of Patagonia includes the provinces of Neuquén, Río Negro, Chubut, Santa Cruz, and Tierra del Fuego, as well as the southern tip of the Buenos Aires Province. The Chilean portion embraces the southern part of the region of Los Lagos, and the regions of Aysen and Magallanes (excluding the portion of Antarctica claimed by Chile).

Patagonia is that portion of South America which, to the east of the Andes, lies south of the Neuquén and Río Colorado rivers, and, to the west of the Andes, south of (42°S). Confined to the eastern part of the region. Pliocene. Sandstones and conglomerates with marine fossils.

Paranfl series. Middle and Upper Miocene. Containing remains of mammals. Santa Cruz series.

Lower Miocene. Partly marine, partly terrestrial. Patagonian Molasse. Eocene and Oligocene.

Of terrestrial origin, containing remains of mammalia. Pyrotherium-Notostylops beds.

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