In the history of Europe, the Middle Ages lasted from the 5th to the 15th century. It began with the fall of the Western Roman Empire and merged into the Renaissance and the Age of Discovery; the Middle Ages is the middle period of the three traditional divisions of Western history: classical antiquity, the medieval period, the modern period. The medieval period is itself subdivided into the Early and Late Middle Ages. Population decline, counterurbanisation, collapse of centralized authority and mass migrations of tribes, which had begun in Late Antiquity, continued in the Early Middle Ages; the large-scale movements of the Migration Period, including various Germanic peoples, formed new kingdoms in what remained of the Western Roman Empire. In the 7th century, North Africa and the Middle East—once part of the Byzantine Empire—came under the rule of the Umayyad Caliphate, an Islamic empire, after conquest by Muhammad's successors. Although there were substantial changes in society and political structures, the break with classical antiquity was not complete.
The still-sizeable Byzantine Empire, Rome's direct continuation, survived in the Eastern Mediterranean and remained a major power. The empire's law code, the Corpus Juris Civilis or "Code of Justinian", was rediscovered in Northern Italy in 1070 and became admired in the Middle Ages. In the West, most kingdoms incorporated the few extant Roman institutions. Monasteries were founded; the Franks, under the Carolingian dynasty established the Carolingian Empire during the 8th and early 9th century. It covered much of Western Europe but succumbed to the pressures of internal civil wars combined with external invasions: Vikings from the north, Magyars from the east, Saracens from the south. During the High Middle Ages, which began after 1000, the population of Europe increased as technological and agricultural innovations allowed trade to flourish and the Medieval Warm Period climate change allowed crop yields to increase. Manorialism, the organisation of peasants into villages that owed rent and labour services to the nobles, feudalism, the political structure whereby knights and lower-status nobles owed military service to their overlords in return for the right to rent from lands and manors, were two of the ways society was organised in the High Middle Ages.
The Crusades, first preached in 1095, were military attempts by Western European Christians to regain control of the Holy Land from Muslims. Kings became the heads of centralised nation-states, reducing crime and violence but making the ideal of a unified Christendom more distant. Intellectual life was marked by scholasticism, a philosophy that emphasised joining faith to reason, by the founding of universities; the theology of Thomas Aquinas, the paintings of Giotto, the poetry of Dante and Chaucer, the travels of Marco Polo, the Gothic architecture of cathedrals such as Chartres are among the outstanding achievements toward the end of this period and into the Late Middle Ages. The Late Middle Ages was marked by difficulties and calamities including famine and war, which diminished the population of Europe. Controversy and the Western Schism within the Catholic Church paralleled the interstate conflict, civil strife, peasant revolts that occurred in the kingdoms. Cultural and technological developments transformed European society, concluding the Late Middle Ages and beginning the early modern period.
The Middle Ages is one of the three major periods in the most enduring scheme for analysing European history: classical civilisation, or Antiquity. The "Middle Ages" first appears in Latin in 1469 as media tempestas or "middle season". In early usage, there were many variants, including medium aevum, or "middle age", first recorded in 1604, media saecula, or "middle ages", first recorded in 1625; the alternative term "medieval" derives from medium aevum. Medieval writers divided history into periods such as the "Six Ages" or the "Four Empires", considered their time to be the last before the end of the world; when referring to their own times, they spoke of them as being "modern". In the 1330s, the humanist and poet Petrarch referred to pre-Christian times as antiqua and to the Christian period as nova. Leonardo Bruni was the first historian to use tripartite periodisation in his History of the Florentine People, with a middle period "between the fall of the Roman Empire and the revival of city life sometime in late eleventh and twelfth centuries".
Tripartite periodisation became standard after the 17th-century German historian Christoph Cellarius divided history into three periods: ancient and modern. The most given starting point for the Middle Ages is around 500, with the date of 476 first used by Bruni. Starting dates are sometimes used in the outer parts of Europe. For Europe as a whole, 1500 is considered to be the end of the Middle Ages, but there is no universally agreed upon end date. Depending on the context, events such as the conquest of Constantinople by the Turks in 1453, Christopher Columbus's first voyage to the Americas in 1492, or the Protestant Reformation in 1517 are sometimes used. English historians use the Battle of Bosworth Field in 1485 to mark the end of the period. For Spain, dates used are the death of King Ferdinand II in 1516, the death of Queen Isabella I of Castile in 1504, or the conquest of Granada in 1492. Historians from Romance-speaking countries tend to divide the Middle Ages into two parts: an earlier "High" and late
Cadillac is an Appellation d'Origine Contrôlée for sweet white wine from the Bordeaux wine region in France. It is located within the Entre-Deux-Mers subregion of Bordeaux, it takes its name from the town of Cadillac. In 2008, the area under cultivation was 128 hectares; the history of wine-growing in the Cadillac area parallels that of the wider Bordeaux wine growing region. Situated within the Premières Côtes de Bordeaux AOC, Cadillac has been a separate AOC since August 10, 1973. Cadillac is a small town tucked between the right bank of the Garonne and the calcareous cliffs of the Entre-Deux-Mers plateau, is about thirty kilometres from Bordeaux; the appellation area includes the communes of Baurech, Cadillac, Cardan, Tabanac, Le Tourne and Villenave-de-Rions. The Cadillac region enjoys the same moderate oceanic climate as the Mérignac meteorological station; the proximity of the Garonne, which runs beneath the wine-growing area, creates a local micro-climate. In autumn the river gives rise to early morning humidity, which dries up in the course of the day, conditions that are conducive to the development of moulds that turn into noble rot.
The appellation area is planted with traditional Bordeaux grape varieties. Sémillon covers 70% of the area. A grape variety with high concentrations of sugar, it has a thin skin which allows the Botrytis cinerea fungus to develop and produce noble rot; the 20% of Sauvignon blanc and Sauvignon gris grapes used add a touch of liveliness to the wine, while the 10% of Muscadelle add a touch of added complexity. The density of planting required is at least 4,500 vines per hectare; the distance between rows should be 2.50 metres at most, the distance between individual vines within the row should be at least 0.85 metres. Pruning of vines should take place annually, before the first leaves have developed. Single and Double Guyot, Cordon de Royat and Gobelet are the permitted pruning methods; the number of buds is limited to a maximum of 12. Once suckering and green harvesting have been completed, the maximum number of clusters allowed per vine is 14. Plots that have been abandoned can no longer be considered part of the AOC area.
Wine-growers must mow or use herbicides to prevent weeds from growing up around the vines, otherwise they could create a humid micro-climate below the leaves that would encourage the development of cryptogamic diseases. They must carry out treatments to keep the occurrence of diseases such as mildew and oidium below the permitted quality thresholds; the proportion of dead or missing vines may not exceed 20% of the total number. If this percentage is exceeded, the final yield must be cut down proportionately. Harvesting is carried out when the grapes are ripe; the degree of ripeness is ascertained by the presence of noble rot or signs of over-maturity, i.e. grapes have begun to dry out on the vine and have become shrivelled, golden-coloured berries. It can be assessed by measuring the sugar content. Before harvesting can begin, it must be shown that the grapes contain at least 255 grams of sugar per litre. Harvesting is carried out manually over multiple successive pickings combined with sorting of the grapes.
The grape-pickers are ordered to pick only those clusters or part-clusters which are either ripe or have heightened sugar content brought about by noble rot. This means. Once they arrive in the wine sheds, the grapes are pressed; the process is carried out in order to allow enough time for the must to be extracted from the dried-out fruits. So, yields of juice are low; the use of machines which break down the grapes is prohibited, i.e. self-emptying tanks with combined rotor crushers and must pumps, continuous screw presses and small diameter screw presses. The must is cooled ready for racking. Afterwards, the must is left to ferment, either in barrels; the fermentation process is lengthy, since the sugar and alcohol slow down the activity of the yeast. Fermentation either stops or is stopped by the wine-grower using cooling and sterile filtering processes: this kind of filtering uses a fine mesh to capture the yeasts that have been anesthetized by the cold. At this stage, the wine is stabilized against possible yeast or bacterial contamination by the addition of sulfites.
The wine is left to mature in vats or barrels for several months and is not allowed to leave the wine sheds before 31 March of the year following the harvest. Quarterly rackings ensure that the lees held in suspension in the wine are removed. Before being bottled, the wine is filtered and the sulfite level is adjusted; the wine has a golden yellow colour that develops over time to a shade of amber. Aromas are fruity and spicy. On the palate, sweetness of aroma and sugar content are balanced by the wine's acidity; the wine is suitable for aging. The wine must have a minimum acquired alcohol content of 12% by volume; the amount of residual sugar must be at least 51 grams per litre. If the wine has been enriched, the potential alcohol content of the wine may not exceed 19% by volume. Premières Côtes de Bordeaux: Cadillac
A raisin is a dried grape. Raisins are produced in many regions of the world and may be eaten raw or used in cooking and brewing. In the United Kingdom, New Zealand, Australia, the word "raisin" is reserved for the dark-colored dried large grape, with "sultana" being a golden-colored dried grape, "currant" being a dried small Black Corinth seedless grape; the word "raisin" is a loanword from Old French. The Old French word, in turn, developed from the Latin word racemus, "a bunch of grapes". Raisin varieties depend on the type of grape used and are made in a variety of sizes and colors including green, brown, blue and yellow. Seedless varieties include the Greek currants and Flame grapes. Raisins are traditionally sun-dried, but may be water-dipped and artificially dehydrated. "Golden raisins" are dried in dehydrators with controlled temperature and humidity, which allows them to retain a lighter color and more moisture. They are treated with sulfur dioxide after drying. Black Corinth or Zante currant are miniature, sometimes seedless raisins that are much darker and have a tart, tangy flavor.
They are called currants. Muscat raisins are large compared to other varieties, sweeter. Several varieties of raisins produced in Asia are available in the West only at ethnic grocers. Monukka grapes are used for some of these. Raisins can contain up to 72% sugars by weight, most of, fructose and glucose – forming sucrose when combined in a single molecule, they contain about 3% protein and 3.7%–6.8% dietary fiber. Raisins, like prunes and apricots, are high in certain antioxidants, but have a lower vitamin C content than fresh grapes. Raisins contain no cholesterol. Data presented at the American College of Cardiology's 61st Annual Scientific Session in 2012 suggest that, among individuals with mild increases in blood pressure, the routine consumption of raisins may lower blood pressure when compared to eating other common snacks. Raisins can cause renal failure in dogs; the cause of this is not known. Raisins are sweet due to their high concentration of sugars; the sugars can crystallise inside the fruit when stored after a long period, making the dry raisins gritty, but that does not affect their usability.
These sugar grains can be dissolved by blanching the fruit in other liquids. Global production in 2016 was 1.2 million metric tons, with the US as the top producer contributing 24% of the global harvest. Raisins are produced commercially by drying harvested grape berries. For a grape berry to dry, water inside the grape must be removed from the interior of the cells onto the surface of the grape where the water droplets can evaporate. However, this diffusion process is difficult because the grape skin contains wax in its cuticle, which prevents the water from passing through. In addition to this, the physical and chemical mechanisms located on the outer layers of the grape are adapted to prevent water loss; the three steps to commercial raisin production include pre-treatment and post-drying processes. Pre-treatment is a necessary step in raisin production to ensure the increased rate of water removal during the drying process. A faster water removal rate decreases the rate of browning and helps to produce more desirable raisins.
The historical method of completing this process was developed in the Mediterranean and Asia Minor areas by using a dry emulsion cold dip made of potassium carbonate and ethyl esters of fatty acids. This dip was shown to increase the rate of water loss by two- to three-fold. New methods have been developed such as exposing the grapes to oil emulsions or dilute alkaline solutions; these methods can encourage water transfer to the outer surface of grapes which helps to increase the efficiency of the drying process. The three types of drying methods are: sun drying, shade drying, mechanical drying. Sun drying is an inexpensive process. Additionally, sun drying is a slow process and may not produce the most desirable raisins. Mechanical drying can be done in a safer and more controlled environment where rapid drying is guaranteed. One type of mechanical drying is to use microwave heating. Water molecules in the grapes absorb microwave energy resulting in rapid evaporation. Microwave heating produces puffy raisins.
After the drying process is complete, raisins are sent to processing plants where they are cleaned with water to remove any foreign objects that may have become embedded during the drying process. Stems and off-grade raisins are removed; the washing process may cause rehydration, so another drying step is completed after washing to ensure that the added moisture has been removed. All steps in the production of raisins are important in determining the quality of raisins. Sometimes, sulfur dioxide is applied to raisins after the pre treatment step and before drying to decrease the rate of browning caused by the reaction between polyphenol oxidase and phenolic compounds. Sulfur dioxide helps to preserve flavor and prevent the loss of certain vitamins during the drying process. Raisins are rich in dietary fiber, carbohydrates with a low glycemic index, minerals like copper and iron, with a low fat content. Raisins are recommended as a snack for weight control bec
Sémillon is a golden-skinned grape used to make dry and sweet white wines in France and Australia. Its thin skin and susceptibility to botrytis make it dominate the sweet wine region Sauternes AOC and Barsac AOC; the Sémillon grape is native to the Bordeaux region. It was known as Sémillon de Saint-Émilion in 1736, while Sémillon resembles the local pronunciation of the town’s name, it first arrived in Australia in the early 19th century and by the 1820s the grape covered over 90 percent of South Africa's vineyards, where it was known as Wyndruif, meaning "wine grape". It was once considered to be the most planted grape in the world, although this is no longer the case. In the 1950s, Chile's vineyards were made up of over 75% Sémillon. Today, it accounts for just 1% of South African Cape vines. Sémillon, easy to cultivate produces six to eight tons of grapes per acre from its vigorous vines, it is resistant to disease, except for rot. The grape ripens early. Since the grape has a thin skin, there is a risk of sunburn in hotter climates.
The Sémillon grape is rather heavy, with low acidity and an oily texture. It has a high yield and wines based on it can age a long time. Along with Sauvignon blanc and Muscadelle, Sémillon is one of only three approved white wine varieties in the Bordeaux region; the grape is key to the production of sweet wines such as Sauternes. For the grapes to be used for sweet wine production, they need to have been affected by Botrytis; this fungus dries out the grapes, thus concentrating the sugar and flavours in the grape berry. Sémillon is an important cultivar in two significant wine producing countries. In France, Sémillon is the preeminent white grape in the Bordeaux wine regions; the grape has found a home in Australia. In France, the Sémillon grape is grown in Bordeaux where it is blended with Sauvignon blanc and Muscadelle; when dry, it is referred to as Bordeaux blanc and is permitted to be made in the appellations of Pessac-Léognan, Entre-Deux-Mers and other less-renowned regions. In this form, Sémillon is a minor constituent in the blend.
However, when used to make the sweet white wines of Bordeaux it is the dominant variety. In such wines the vine is exposed to the "noble rot" of Botrytis cinerea which consumes the water content of the fruit, concentrating the sugar present in its pulp; when attacked by Botrytis cinerea, the grapes shrivel and the acid and sugar levels are intensified. Due to the declining popularity of the grape variety, fewer clones are cultivated in nurseries causing producers to project a future shortage of quality wine. In 2008, 17 Bordeaux wine producers, including Château d'Yquem, Château Olivier, Château Suduiraut and Château La Tour Blanche, formed an association to grow their own clones. Sémillon is grown in Australia in the Hunter Valley north of Sydney, where for a long time it was known as "Hunter River Riesling". Four styles of Sémillon-based wines are made there: a commercial style blended with Chardonnay or Sauvignon blanc; the latter two styles were pioneered by Lindemans, Tulloch, McWilliam's Elizabeth, Drayton's and Tyrrell's, are considered unique to Australia.
Most examples of these bottle-aged Hunter Semillons exhibit a buttercup-yellow colour, burnt toast or honey characteristics on the nose and excellent complex flavours on the palate, with a long finish and soft acid. Young Hunter Valley semillon is always a dry wine exhibiting citrus flavours of lemon, lime or green apple. Cooler-year Hunter Semillons seem to be the most sought after, with some of the 1974 and 1977 vintages still drinking well; the newer, fruit-accentuated styles are championed by the likes of Iain Riggs at Brokenwood Wines and The Rothbury Estate. Sémillon is finding favour with Australian producers outside the Hunter Valley in the Barossa Valley and Margaret River regions; the Adelaide Hills is becoming a flourishing region for Semillon, with the cooler climate producing some wines of great complexity. Vineyards such as Amadio and Paracombe produce some premium blends of the classical style. Semillon is one of the Cape’s true heritage white varietals, with origins as early as the 17th century, the grape variety accounted for more than 90% of plantings in the first half of the 19th century.
While South African Semillon has not quite taken off as a serious commercial category in single varietal form in the modern era, there are stunning wines being made from older vineyards. More the variety plays a role in beefing up the volume of Sauvignon blancs; the best South African Semillons have juicy fruit with an ethereal-like citrus perfume, fine texture, herbal interest and manage to marry the intensity of flavour with finesse. Outside of these regions, however, Sémillon is unpopular and criticised for lack of complexity and intensity; as such, plantings have decreased over the last century. As referenced above, the grape can still be found in South Chile; the latter is reputed to have the largest plantin
Germany the Federal Republic of Germany, is a country in Central and Western Europe, lying between the Baltic and North Seas to the north, the Alps to the south. It borders Denmark to the north and the Czech Republic to the east and Switzerland to the south, France to the southwest, Luxembourg and the Netherlands to the west. Germany includes 16 constituent states, covers an area of 357,386 square kilometres, has a temperate seasonal climate. With 83 million inhabitants, it is the second most populous state of Europe after Russia, the most populous state lying in Europe, as well as the most populous member state of the European Union. Germany is a decentralized country, its capital and largest metropolis is Berlin, while Frankfurt serves as its financial capital and has the country's busiest airport. Germany's largest urban area is the Ruhr, with its main centres of Essen; the country's other major cities are Hamburg, Cologne, Stuttgart, Düsseldorf, Dresden, Bremen and Nuremberg. Various Germanic tribes have inhabited the northern parts of modern Germany since classical antiquity.
A region named Germania was documented before 100 AD. During the Migration Period, the Germanic tribes expanded southward. Beginning in the 10th century, German territories formed a central part of the Holy Roman Empire. During the 16th century, northern German regions became the centre of the Protestant Reformation. After the collapse of the Holy Roman Empire, the German Confederation was formed in 1815; the German revolutions of 1848–49 resulted in the Frankfurt Parliament establishing major democratic rights. In 1871, Germany became a nation state when most of the German states unified into the Prussian-dominated German Empire. After World War I and the revolution of 1918–19, the Empire was replaced by the parliamentary Weimar Republic; the Nazi seizure of power in 1933 led to the establishment of a dictatorship, the annexation of Austria, World War II, the Holocaust. After the end of World War II in Europe and a period of Allied occupation, Austria was re-established as an independent country and two new German states were founded: West Germany, formed from the American and French occupation zones, East Germany, formed from the Soviet occupation zone.
Following the Revolutions of 1989 that ended communist rule in Central and Eastern Europe, the country was reunified on 3 October 1990. Today, the sovereign state of Germany is a federal parliamentary republic led by a chancellor, it is a great power with a strong economy. As a global leader in several industrial and technological sectors, it is both the world's third-largest exporter and importer of goods; as a developed country with a high standard of living, it upholds a social security and universal health care system, environmental protection, a tuition-free university education. The Federal Republic of Germany was a founding member of the European Economic Community in 1957 and the European Union in 1993, it is part of the Schengen Area and became a co-founder of the Eurozone in 1999. Germany is a member of the United Nations, NATO, the G7, the G20, the OECD. Known for its rich cultural history, Germany has been continuously the home of influential and successful artists, musicians, film people, entrepreneurs, scientists and inventors.
Germany has a large number of World Heritage sites and is among the top tourism destinations in the world. The English word Germany derives from the Latin Germania, which came into use after Julius Caesar adopted it for the peoples east of the Rhine; the German term Deutschland diutisciu land is derived from deutsch, descended from Old High German diutisc "popular" used to distinguish the language of the common people from Latin and its Romance descendants. This in turn descends from Proto-Germanic *þiudiskaz "popular", derived from *þeudō, descended from Proto-Indo-European *tewtéh₂- "people", from which the word Teutons originates; the discovery of the Mauer 1 mandible shows that ancient humans were present in Germany at least 600,000 years ago. The oldest complete hunting weapons found anywhere in the world were discovered in a coal mine in Schöningen between 1994 and 1998 where eight 380,000-year-old wooden javelins of 1.82 to 2.25 m length were unearthed. The Neander Valley was the location where the first non-modern human fossil was discovered.
The Neanderthal 1 fossils are known to be 40,000 years old. Evidence of modern humans dated, has been found in caves in the Swabian Jura near Ulm; the finds included 42,000-year-old bird bone and mammoth ivory flutes which are the oldest musical instruments found, the 40,000-year-old Ice Age Lion Man, the oldest uncontested figurative art discovered, the 35,000-year-old Venus of Hohle Fels, the oldest uncontested human figurative art discovered. The Nebra sky disk is a bronze artefact created during the European Bronze Age attributed to a site near Nebra, Saxony-Anhalt, it is part of UNESCO's Memory of the World Programme. The Germanic tribes are thought to date from the Pre-Roman Iron Age. From southern Scandinavia and north Germany, they expanded south and west from the 1st century BC, coming into contact with the Celtic tribes of Gaul as well
Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, resulting in a phase change from water vapor to ice as the water vapor reaches the freezing point. In temperate climates, it most appears on surfaces near the ground as fragile white crystals; the propagation of crystal formation occurs by the process of nucleation. The ice crystals of frost form as the result of fractal process development; the depth of frost crystals varies depending on the amount of time they have been accumulating, the concentration of the water vapor. Frost crystals may be clear, or white. Types of frost include crystalline frost from deposition of water vapor from air of low humidity, white frost in humid conditions, window frost on glass surfaces, advection frost from cold wind over cold surfaces, black frost without visible ice at low temperatures and low humidity, rime under supercooled wet conditions.
Plants that have evolved in warmer climates suffer damage when the temperature falls low enough to freeze the water in the cells that make up the plant tissue. The tissue damage resulting from this process is known as "frost damage". Farmers in those regions where frost damage is known to affect their crops invest in substantial means to protect their crops from such damage. If a solid surface is chilled below the dew point of the surrounding humid air and the surface itself is colder than freezing, ice will form on it. If the water deposits as a liquid that freezes, it forms a coating that may look glassy, opaque, or crystalline, depending on its type. Depending on context, that process may be called atmospheric icing; the ice it produces differs in some ways from crystalline frost, which consists of spicules of ice that project from the solid surface on which they grow. The main difference between the ice coatings and frost spicules arises from the fact that the crystalline spicules grow directly from desublimation of water vapour from air, desublimation is not a factor in icing of freezing surfaces.
For desublimation to proceed the surface must be below the frost point of the air, meaning that it is sufficiently cold for ice to form without passing through the liquid phase. The air must be humid, but not sufficiently humid to permit the condensation of liquid water, or icing will result instead of desublimation; the size of the crystals depends on the temperature, the amount of water vapor available, how long they have been growing undisturbed. As a rule, except in conditions where supercooled droplets are present in the air, frost will form only if the deposition surface is colder than the surrounding air. For instance frost may be observed around cracks in cold wooden sidewalks when humid air escapes from the warmer ground beneath. Other objects on which frost forms are those with low specific heat or high thermal emissivity, such as blackened metals; the erratic occurrence of frost in adjacent localities is due to differences of elevation, the lower areas becoming colder on calm nights.
Where static air settles above an area of ground in the absence of wind, the absorptivity and specific heat of the ground influence the temperature that the trapped air attains. Hoar frost hoarfrost, radiation frost, or pruina, refers to white ice crystals deposited on the ground or loosely attached to exposed objects, such as wires or leaves, they form on cold, clear nights when conditions are such that heat radiates out to the open air faster than it can be replaced from nearby sources, such as wind or warm objects. Under suitable circumstances, objects cool to below the frost point of the surrounding air, well below the freezing point of water; such freezing may be promoted by effects such as frost pocket. These occur when ground-level radiation losses cool air until it flows downhill and accumulates in pockets of cold air in valleys and hollows. Hoar frost may freeze in such low-lying cold air when the air temperature a few feet above ground is well above freezing; the word hoar comes from an Old English adjective that means "showing signs of old age".
In this context, it refers to the frost that makes bushes look like white hair. Hoar frost may have different names depending on where it forms: Air hoar is a deposit of hoar frost on objects above the surface, such as tree branches, plant stems, wires. Surface hoar refers to fern-like ice crystals directly deposited on snow, ice or frozen surfaces. Crevasse hoar consists of crystals that form in glacial crevasses where water vapour can accumulate under calm weather conditions. Depth hoar refers to faceted crystals that have grown large within cavities beneath the surface of banks of dry snow. Depth hoar crystals grow continuously at the expense of neighbouring smaller crystals, so are visibly stepped and have faceted hollows; when surface hoar covers sloping snowbanks, the layer of frost crystals may create an avalanche risk. Ideal conditions for hoarfrost to form on snow are cold clear nights, with light, cold air currents conveying humidity at the right rate for growth of frost crystals. Wind, too strong or war