question: Why do the spires on gothic cathedrals have those knobs on them?
comment: The spires are called [pinnacles]( URL_0 ), and the knobs are called [crockets]( URL_1 ), and are ornamental. According to this [PDF]( URL_2 ) they help direct the flow and drip of water away from the walls (no eaves).
passages: At the base of the central support beam of the spire, an iron plaque dedicated to the achievement of the workers was inscribed with the image of a compass and a try square. These were the symbols of the mason's guild and a subtle reference to God's role as Great Architect of the Universe in Catholic tradition. Because both Viollet-le-Duc and Bellu are both mentioned by name on the plaque, it has been theorized that they were Freemasons.
   The left portal is more enigmatic and art historians still argue over the correct identification. The tympanum shows Christ standing on a cloud, apparently supported by two angels. Some see this as a depiction of the Ascension of Christ (in which case the figures on the lower lintel would represent the disciples witnessing the event) while others see it as representing the "Parousia", or Second Coming of Christ (in which case the lintel figures could be either the prophets who foresaw that event or else the 'Men of Galilee' mentioned in Acts 1:9-11). The presence of angels in the upper lintel, descending from a cloud and apparently shouting to those below, would seem to support the latter interpretation. The archivolts contain the signs of the zodiac and the labours of the months – standard references to the cyclical nature of time which appear in many gothic portals.
   Some have stated that there were no pinnacles in the Romanesque style, but conical caps to circular buttresses, with finial terminations, are not uncommon in France at very early periods. Eugène Viollet-le-Duc gives examples from St Germer and St Remi, and there is one of similar form at the west front of Rochester Cathedral.
   Also on this panel one can see the French Gothic influence. Above the two Roman matrons emerges an image of an Gothic arch and “the character of this architecture, its relative elegance and thinness of proportions, suggests transalpine influence”
  
  Journey and Adoration of the Magi
   There is also a type of analogion which is used in the kliros by the chanters. This often has two or three sides and turns to allow the singers to more easily use the numerous liturgical texts required during the services.
  
  There is an older Greek design for this type of analogion that is octagonal with a flat top instead of slanted. This style is still found in use on Mount Athos and at other ancient monasteries throughout the world. Sometimes this type of analogion is intricately inlaid with mother of pearl or other semi-precious materials.
   In Alberobello, atop the cone of a trullo, there is normally a hand-worked sandstone pinnacle ("pinnacolo"), that may be one of many designs - disk, ball, cone, bowl, polyhedron, or a combination thereof, that is supposed to be the signature of the stonemason who built the trullo.
  
  Section::::Architecture.:Whitewashed symbols.
   The Romanesque Norwich Cathedral in Norfolk, England, has the largest number of painted carved stone bosses in the world; an extensive and varied collection of over one thousand individual pieces. Many of these decorated bosses still bare the original gilt and pigments from the time of their creation.
   During the 19th century the Gothic revival knew no bounds. With advances in technology, steel production, and building techniques the spire enjoyed an unprecedented surge through architecture, Cologne Cathedral's famous spires, designed centuries earlier, were finally completed in this era.
  
  Spires have never really fallen out of fashion. In the twentieth century reinforced concrete offered new possibilities for openwork spires.
  
  Section::::Traditional types of spires.
  
  BULLET::::- Conical stone spires: These are usually found on circular towers and turrets, usually of small diameter.
   Each feature of the Cathedral had a symbolic meaning. The main portals at Notre Dame de Paris, for instance, represented the entrance to paradise, with the last judgement depicted on the tympanum over the doors, showing Christ surrounded by the apostles, and by the signs of the zodiac, representing the movements of the heavens. The columns below the tympanum are in the form of statues of saints, literally reprinting them as "the pillars of the church."
   As an architectural ornament, spires are most consistently found on Christian churches, where they replace the steeple. Although any denomination may choose to use a spire instead of a steeple, the lack of a cross on the structure is more common in Roman Catholic and other pre-Reformation churches. The battlements of cathedrals featured multiple spires in the Gothic style (in imitation of the secular military fortress).
  
  Section::::Gothic and neo-gothic spires.
   Section::::History.:Rounded quadrifoils.
   BULLET::::- The towers have a very strong vertical emphasis with massive polygonal buttress which cast "vertical shadows" in the slanting sun. The deeply recessed archways have the same effect, while the sculpture screen is "opposingly horizontal".
  
  BULLET::::- The dominant decorative features internally are the contrast of the "dark marble mouldings" and ribs against the pale masonry, the "regular repetition" of arcading and the multiplicity of rib vaults. The effect of regular repetition of simple forms is seen externally on the screen and in the arrangement of windows.
   In Sicily there are a number of palaces and churches where the pointed arch is used during this period, apparently adopted from Islamic architecture.
  
  Section::::Characteristics.:Architectural embellishment and sculpture.
   One of the cathedral's builders, Matthew Roriczer, created and taught a way to take an elevation through a ground plan. This technique used to find the elevation does through a square, and from this square he was able to develop the proportions of the cathedral's pinnacles.
   The crown of the facade is formed by the last floor, which does not have a rostrum, and the coronation elements, with rounded shapes, which include a thin tooth finished with a dome, shaped like an onion covered with scales.
   Amid all the religious figures, some of the sculptural decoration was devoted to illustrating medieval science and philosophy. The porch of Notre Dame Cathedral in Paris and of Amiens Cathedral are decorated with similar small carved figures holding circular plaques with symbols of transformation taken from alchemy. The central pillar of the central door of Notre Dame features a statue of a woman on a throne holding a scepter in her left hand, and in her right hand, two books, one open (symbol of public knowledge), and the other closed (esoteric knowledge), along with a ladder with seven steps, symbolizing the seven steps alchemists followed in their scientific quest of trying to transform ordinary metal into gold.
   The last step in evolution of the Gothic style was to set the rose into a tier of vertical lights, of staggered height and surmount it by a tapering pointed light so that it became the centre of a vast window composition, covering the whole end of the transepts, as in Rouen or Beauvais Cathedrals. This sort of elaborate composition can also be seen at the east end of Milan Cathedral.
   The tower's "Gate of Life" was made by János Bille in 1931 and explains a Christian life through symbols. At the top and at the bottom, there are two numbers: 1272 and 1931. The former was thought to represent the year in which the upper part was built, while 1931 is when it was turned to a baptismal chapel. There are 20 symbols, not including the numbers, the first one an Alpha and the last an Omega. The Alpha and the Omega were symbols of Jesus Christ, and birth and death.
  
  Section::::References.
   BULLET::::- Plate Tracery: Rose windows with pierced openings rather than tracery occur in the transition between Romanesque and Gothic, particularly in France and most notably at Chartres. The most notable example in England is the north transept window, known as the "Dean's Eye" in Lincoln Cathedral. These windows are occasionally found in 19th-century Revival buildings.
   Section::::Gothic influence.
   In the late Gothic periods the buttresses became extremely ornate, with a large amount of non-functional decoration in the form of pinnacles, curving arches, counter-curves, statuary and ornamental pendants.
  
  Section::::Elements of Gothic style.:Height.
   Section::::History.:Verge and foliot clocks.
   Above all, the famous west front, decorated with thousands of figures, is a masterpiece of the Gothic era. The tower is one of the first to rely substantially on craftsmanship, with the final appearance being one with a high degree of linearity captured in stone. While previous façades were certainly drawn prior to construction, Strasbourg has one of the earliest façades whose construction is inconceivable without prior drawing. Strasbourg and Cologne Cathedral together represent some of the earliest uses of architectural drawing. The work of Professor Robert O. Bork of the University of Iowa suggests that the design of the Strasbourg façade, while seeming almost random in its complexity, can be constructed using a series of rotated octagons. The west front of the cathedral was the work of chief architect ("magister operis") Erwin von Steinbach. Erwin von Steinbach's son Johannes von Steinbach served as "magister operis" from (at least) 1332 until his death in 1341. From 1341 until 1372, the post of chief architect was held by a Master Gerlach about whom little is known (not to be confused with Erwin's son Gerlach), and in the years 1383–1387, a Michael von Freiburg (also known as Michael von Gmünd, or Michael Parler, from the Parler family) is recorded as "magister operis"; he was succeeded by Claus von Lohre (1388−1399).
   The clock is also one of the few existing monumental clocks which turns anti-clockwise.
  
  The chimes inside the clock (10 bells, tonal range of –f) can be operated from the cathedral organ.
  
  Section::::Astronomical clock.:History.
   Section::::Evolution of use.
  
raw_presuppositions: Gothic cathedrals have spires and knob. Sprires on gothic cathedrals have knobs on them.
raw_corrections: Gothic cathedrals do not have spires and knobs, gothic cathedrals have pinnacles and crockets. Spires on gothic cathedrals have ornamental crockets on them.