Clock

A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece. In general usage today a "clock" refers to any device for measuring and displaying the time. Watches and other timepieces that can be carried on one's person are often distinguished from clocks.
The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today.

Sundials and other devices

The sundial, which measures the time of day by using the sun casting a shadow onto a cylindrical stone, was widely used in ancient times. A well-constructed sundial can measure local solar time with reasonable accuracy, and sundials continued to be used to monitor the performance of clocks until the modern era. However, its practical limitations—it requires the sun to shine and does not work at all during the night—encouraged the use of other techniques for measuring time.
Candle clocks and sticks made of incense that burn down at approximately predictable speeds have also been used to estimate the passing of time. In an hourglass, fine sand pours through a tiny hole at a constant rate and indicates a predetermined passage of an arbitrary period of time.

Water clocks

Water clocks, also known as clepsydrae (sg: clepsydra), along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical gnomon and the day counting tally stick. Given their great antiquity, where and when they first existed is not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC in these regions of the world.
Greek astronomer Andronicus of Cyrrhus supervised the construction of the Tower of the Winds in Athens in the 1st century B.C.
The Greek and Roman civilizations are credited for initially advancing water clock design to include complex gearing, which was connected to fanciful automata and also resulted in improved accuracy. These advances were passed on through Byzantium and Islamic times, eventually making their way back to Europe. Independently, the Chinese developed their own advanced water clocks（水鐘）in 725 A.D., passing their ideas on to Korea and Japan.
Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. Pre-modern societies do not have the same precise timekeeping requirements that exist in modern industrial societies, where every hour of work or rest is monitored, and work may start or finish at any time regardless of external conditions. Instead, water clocks in ancient societies were used mainly for astrological reasons. These early water clocks were calibrated with a sundial. While never reaching the level of accuracy of a modern timepiece, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by the more accurate pendulum clock in 17th century Europe.
Islamic civilization is credited with further advancing the accuracy of clocks with elaborate engineering. In 797 (or possibly 801), the Abbasid caliph of Baghdad, Harun al-Rashid, presented Charlemagne with an Asian Elephant named Abul-Abbas together with a "particularly elaborate example" of a water clock.
In the 13th century, Al-Jazari, a Kurdish Muslim engineer from Mesopotamia (lived 1136-1206) who worked for Artuqid king of Diyar-Bakr, Nasir al-Din, made numerous clocks of all shapes and sizes. The book described 50 mechanical devices in 6 categories, including water clocks. The most reputed clocks included the Elephant, Scribe and Castle clocks, all of which have been successfully reconstructed. As well as telling the time, these grand clocks were symbols of status, grandeur and wealth of the Urtuq State.

Early mechanical clocks

None of the first clocks survived from 13th century Europe, but various mentions in church records reveal some of the early history of the clock.
The word horologia (from the Greek ὡρα, hour, and λέγειν, to tell) was used to describe all these devices, but the use of this word (still used in several Romance languages) for all timekeepers conceals from us the true nature of the mechanisms. For example, there is a record that in 1176 Sens Cathedral installed a ‘horologe’  but the mechanism used is unknown. According to Jocelin of Brakelond, in 1198 during a fire at the abbey of St Edmundsbury (now Bury St Edmunds), the monks 'ran to the clock' to fetch water, indicating that their water clock had a reservoir large enough to help extinguish the occasional fire.

A new mechanism

The word clock (from the Celtic words clocca and clogan, both meaning "bell"), which gradually supersedes "horologe", suggests that it was the sound of bells which also characterized the prototype mechanical clocks that appeared during the 13th century in Europe.
Outside Europe, the escapement mechanism had been known and used in medieval China, as the Song Dynasty horologist and engineer Su Song (1020–1101) incorporated it into his astronomical clock-tower of Kaifeng in 1088.  However, his astronomical clock and rotating armillary sphere still relied on the use of flowing water (i.e. hydraulics), while European clockworks of the following centuries shed this old method for a more efficient driving power of weights, in addition to the escapement mechanism.
A mercury clock, described in the Libros del saber, a Spanish work from 1277 consisting of translations and paraphrases of Arabic works, is sometimes quoted as evidence for Muslim knowledge of a mechanical clock. The first mercury powered automata clock was invented by Ibn Khalaf al-Muradi.
Between 1280 and 1320, there is an increase in the number of references to clocks and horologes in church records, and this probably indicates that a new type of clock mechanism had been devised. Existing clock mechanisms that used water power were being adapted to take their driving power from falling weights. This power was controlled by some form of oscillating mechanism, probably derived from existing bell-ringing or alarm devices. This controlled release of power - the escapement - marks the beginning of the true mechanical clock.
These mechanical clocks were intended for two main purposes: for signalling and notification (e.g. the timing of services and public events), and for modeling the solar system. The former purpose is administrative, the latter arises naturally given the scholarly interest in astronomy, science, astrology, and how these subjects integrated with the religious philosophy of the time. The astrolabe was used both by astronomers and astrologers, and it was natural to apply a clockwork drive to the rotating plate to produce a working model of the solar system.
Simple clocks intended mainly for notification were installed in towers, and did not always require faces or hands. They would have announced the canonical hours or intervals between set times of prayer. Canonical hours varied in length as the times of sunrise and sunset shifted. The more sophisticated astronomical clocks would have had moving dials or hands, and would have shown the time in various time systems, including Italian hours, canonical hours, and time as measured by astronomers at the time. Both styles of clock started acquiring extravagant features such as automata.
In 1283, a large clock was installed at Dunstable Priory; its location above the rood screen suggests that it was not a water clock. In 1292, Canterbury Cathedral installed a 'great horloge'. Over the next 30 years there are brief mentions of clocks at a number of ecclesiastical institutions in England, Italy, and France. In 1322, a new clock was installed in Norwich, an expensive replacement for an earlier clock installed in 1273. This had a large (2 metre) astronomical dial with automata and bells. The costs of the installation included the full-time employment of two clockkeepers for two years

Early astronomical clocks

Besides the Chinese astronomical clock of Su Song in 1088 mentioned above, in Europe there were the clocks constructed by Richard of Wallingford in St Albans by 1336, and by Giovanni de Dondi in Padua from 1348 to 1364. They no longer exist, but detailed descriptions of their design and construction survive, and modern reproductions have been made.  They illustrate how quickly the theory of the mechanical clock had been translated into practical constructions, and also that one of the many impulses to their development had been the desire of astronomers to investigate celestial phenomena.
Wallingford's clock had a large astrolabe-type dial, showing the sun, the moon's age, phase, and node, a star map, and possibly the planets. In addition, it had a wheel of fortune and an indicator of the state of the tide at London Bridge. Bells rang every hour, the number of strokes indicating the time.
Dondi's clock was a seven-sided construction, 1 metre high, with dials showing the time of day, including minutes, the motions of all the known planets, an automatic calendar of fixed and movable feasts, and an eclipse prediction hand rotating once every 18 years.
It is not known how accurate or reliable these clocks would have been. They were probably adjusted manually every day to compensate for errors caused by wear and imprecise manufacture.
Water clocks are sometimes still used today, and can be examined in places such as ancient castles and museums.
The Salisbury Cathedral clock, built in 1386, is considered to be the world's oldest surviving mechanical clock that strikes the hours.

Later developments

Clockmakers developed their art in various ways. Building smaller clocks was a technical challenge, as was improving accuracy and reliability. Clocks could be impressive showpieces to demonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The escapement in particular was an important factor affecting the clock's accuracy, so many different mechanisms were tried.
Spring-driven clocks appeared during the 15th century, although they are often erroneously credited to Nuremberg watchmaker Peter Henlein (or Henle, or Hele) around 1511. The earliest existing spring driven clock is the chamber clock given to Peter the Good, Duke of Burgundy, around 1430, now in the Germanisches Nationalmuseum. Spring power presented clockmakers with a new problem: how to keep the clock movement running at a constant rate as the spring ran down. This resulted in the invention of the stackfreed and the fusee in the 15th century, and many other innovations, down to the invention of the modern going barrel in 1760.
Early clock dials did not indicate minutes and seconds. A clock with a dial indicating minutes was illustrated in a 1475 manuscript by Paulus Almanus, and some 15th-century clocks in Germany indicated minutes and seconds. An early record of a seconds hand on a clock dates back to about 1560 on a clock now in the Fremersdorf collection.  However, this clock could not have been accurate, and the seconds hand was probably for indicating that the clock was working.
During the 15th and 16th centuries, clockmaking flourished, particularly in the metalworking towns of Nuremberg and Augsburg, and in Blois, France. Some of the more basic table clocks have only one time-keeping hand, with the dial between the hour markers being divided into four equal parts making the clocks readable to the nearest 15 minutes. Other clocks were exhibitions of craftsmanship and skill, incorporating astronomical indicators and musical movements. The cross-beat escapement was invented in 1584 by Jost Bürgi, who also developed the remontoire. Bürgi's clocks were a great improvement in accuracy as they were correct to within a minute a day.  These clocks helped the 16th-century astronomer Tycho Brahe to observe astronomical events with much greater precision than before.
A mechanical weight-driven astronomical clock with a verge-and-foliot escapement, a striking train of gears, an alarm, and a representation of the moon's phases was described by the Ottoman engineer Taqi al-Din in his book, The Brightest Stars for the Construction of Mechanical Clocks (Al-Kawākib al-durriyya fī wadh' al-bankāmat al-dawriyya), published in 1556-1559. Similarly to earlier 15th-century European alarm clocks,  it was capable of sounding at a specified time, achieved by placing a peg on the dial wheel. At the requested time, the peg activated a ringing device. The clock had three dials which indicated hours, degrees and minutes. He later made an observational clock for the Istanbul observatory of Taqi al-Din (1577–1580), describing it as "a mechanical clock with three dials which show the hours, the minutes, and the seconds." This was an important innovation in 16th-century practical astronomy, as at the start of the 16th century clocks were not accurate enough to be used for astronomical purposes.
The next development in accuracy occurred after 1656 with the invention of the pendulum clock. Galileo had the idea to use a swinging bob to regulate the motion of a time-telling device earlier in the 17th century. Christiaan Huygens, however, is usually credited as the inventor. He determined the mathematical formula that related pendulum length to time (99.38 cm or 39.13 inches for the one second movement) and had the first pendulum-driven clock made. In 1670, the English clockmaker William Clement created the anchor escapement, an improvement over Huygens' crown escapement.  Within just one generation, minute hands and then second hands were added.
In the late 17th and 18th Centuries, equation clocks were made, which allowed the user to see or calculate apparent solar time, as would be shown by a sundial. Before the invention of the pendulum clock, sundials were the only accurate timepieces. When good clocks became available, they appeared inaccurate to people who were used to trusting sundials. The annual variation of the equation of time made a clock up to about 15 minutes fast or slow, relative to a sundial, depending on the time of year. Equation clocks satisfied the demand for clocks that always agreed with sundials. Several types of equation clock mechanism were devised. which can be seen in surviving examples, mostly in museums.
A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The position of a ship at sea could be determined with reasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10 seconds per day. This clock could not contain a pendulum, which would be virtually useless on a rocking ship. Many European governments offered a large prize for anyone who could determine longitude accurately; for example, Great Britain offered 20,000 pounds, equivalent to millions of dollars today. The reward was eventually claimed in 1761 by John Harrison, who dedicated his life to improving the accuracy of his clocks. His H5 clock was in error by less than 5 seconds over 10 weeks.
The excitement over the pendulum clock had attracted the attention of designers, resulting in a proliferation of clock forms. Notably, the longcase clock (also known as the grandfather clock) was created to house the pendulum and works. The English clockmaker William Clement is also credited with developing this form in 1670 or 1671. It was also at this time that clock cases began to be made of wood and clock faces to utilize enamel as well as hand-painted ceramics.
On November 17, 1797, Eli Terry received his first patent for a clock. Terry is known as the founder of the American clock-making industry.
Starting in the U.S. in early decades of the 19th century, clocks were one of the first items to be mass produced and also to use interchangeable parts.
Alexander Bain, Scottish clockmaker, patented the electric clock in 1840. The electric clock's mainspring is wound either with an electric motor or with an electro-magnet and armature. In 1841, he first patented the electromagnetic pendulum.
The development of electronics in the 20th century led to clocks with no clockwork parts at all. Time in these cases is measured in several ways, such as by the vibration of a tuning fork, the behaviour of quartz crystals, or the quantum vibrations of atoms. Even mechanical clocks have since come to be largely powered by batteries, removing the need for winding.

Health benefits of milk

Consumption of milk and dairy products is associated with numerous health benefits.

Bone health

Milk and dairy products are providers of calcium, phosphorous, magnesium and protein which are all essential for healthy bone growth and development.
Adequate consumption of milk and dairy from early childhood and throughout life can help to make the bones strong and protect them against diseases like osteoporosis (a debilitating, brittle bone disorder) in later life.

Teeth

The amounts of calcium and phosphorous in milk and dairy products are also beneficial for the development and maintenance of healthy teeth.
The most abundant protein in milk is casein and is protective as it forms a thin film on the enamel surface which prevents loss of calcium and phosphate from the enamel when the teeth are exposed to acids in the mouth.
Studies have suggested that milk also reduces the effects of cariogenic foods on teeth when consumed together with them in the diet.
In fact, dentists recommend that milk is the only safe drink to have between meals (except for water) as it has been shown not to cause tooth decay even in conditions perfect for damaging teeth!

Milk and blood pressure

An increasing number of studies suggest that consuming 3 portions of dairy each day, along with 5 portions of fruit and vegetables as part of a low salt diet can reduce high blood pressure in both adults and children.
Although the exact mechanisms involved are not clear, it is thought that the calcium, potassium, magnesium and proteins within milk are all likely to be involved.

Milk and cardiovascular disease

Several studies have linked milk and dairy consumption with a reduced risk for cardiovascular disease.
A recent study in Welsh men found that those who drank the most milk had fewer heart attacks than those who had little or no milk in their diets.
This connection could be due to many factors in milk, but epidemiological studies have shown that higher intakes of calcium in particular are linked to a reduced risk of cardiovascular disease.
More specifically, studies have shown that high calcium intakes may reduce high levels of bad cholesterol in the blood, and increase low levels of good cholesterol both of which are known risk factors for cardiovascular disease.
In addition, it is also thought that calcium may bind harmful fats together in the gut and prevent their absorption, which in turn prevents levels in the blood increasing.

Obesity

Contrary to popular belief, research has shown that people who consume milk and dairy foods are likely to be slimmer than those who do not.
Studies have also shown that consumption of milk and dairy foods as part of a calorie controlled diet is associated with increased weight loss, particularly form the abdomen.
This is particularly beneficial since excess fat around the trunk region of the body is associated with greater risks to health.
The precise mechanisms involved are unclear but are likely to involve calcium which is found in milk and dairy foods.

Type 2 diabetes

Studies suggest that regular consumption of low fat dairy products can help to reduce the risk of type 2 diabetes, which has been a longstanding problem in adults, and is becoming increasingly common in children and adolescents.
A recent study of more than 37,000 middle aged women found that those with the highest intakes of dairy had a reduced risk of type 2 diabetes.
The strongest association was found with low fat dairy products.
Similarly a study of men in 2005 found a reduced risk of type 2 diabetes with increased consumption of low fat dairy, interestingly, every extra portion of dairy consumed was associated with increasingly lower risk.
It is thought that this effect may be due to the combined effects of many beneficial nutrients found within dairy foods including calcium and magnesium, or the fact that dairy foods have a low glycaemic index, which helps to control blood sugar levels.

Cancer

There is considerable evidence to suggest that milk has a protective effect on risk of both colorectal and breast cancer with increased intakes.
A recent study of 45,000 Swedish men reported that men who drank 1.5 glasses of milk per day or more, had 35% lower risk of the disease than those who had a low milk intake of less than 2 glasses per week.
Additionally a study of over 40,000 Norwegian women found that those who drank milk as children and continued to do so as adults, had a lower risk of developing breast cancer.
Calcium and a naturally occurring fat in dairy products known as Conjugated Linoleic Acid (CLA) have been suggested as protective components in colon cancer.

Hydration

In order to remain adequately hydrated, it is recommended that we consume 6-8 cups of fluid each day.
If we become dehydrated, it can result in poor concentration and memory function and leave you feeling irritable and unwell.
Milk is an excellent choice of fluid as it not only re-hydrates the body, but provides a host of beneficial nutrients and protects the teeth at the same time!
Re-hydration after exercise is particularly important to replace lost fluids, and a recent study in the USA found that chocolate milk helped the body to recover after exhausting exercise!

A Brief History of the Guitar

by Paul Guy

The guitar is an ancient and noble instrument, whose history can be traced back over 4000 years. Many theories have been advanced about the instrument's ancestry. It has often been claimed that the guitar is a development of the lute, or even of the ancient Greek kithara. Research done by Dr. Michael Kasha in the 1960's showed these claims to be without merit. He showed that the lute is a result of a separate line of development, sharing common ancestors with the guitar, but having had no influence on its evolution. The influence in the opposite direction is undeniable, however - the guitar's immediate forefathers were a major influence on the development of the fretted lute from the fretless oud which the Moors brought with them to to Spain.

The sole "evidence" for the kithara theory is the similarity between the greek word "kithara" and the Spanish word "quitarra". It is hard to imagine how the guitar could have evolved from the kithara, which was a completely different type of instrument - namely a square-framed lap harp, or "lyre". (Right)

It would also be passing strange if a square-framed seven-string lap harp had given its name to the early Spanish 4-string "quitarra". Dr. Kasha turns the question around and asks where the Greeks got the name "kithara", and points out that the earliest Greek kitharas had only 4 strings when they were introduced from abroad. He surmises that the Greeks hellenified the old Persian name for a 4-stringed instrument, "chartar". (See below.)

The Ancestors

The earliest stringed instruments known to archaeologists are bowl harps and tanburs. Since prehistory people have made bowl harps using tortoise shells and calabashes as resonators, with a bent stick for a neck and one or more gut or silk strings. The world's museums contain many such "harps" from the ancient Sumerian, Babylonian, and Egyptian civilisations. Around 2500 - 2000 CE more advanced harps, such as the opulently carved 11-stringed instrument with gold decoration found in Queen Shub-Ad's tomb, started to appear.

"Queen Shub-Ad's harp" (from the Royal Cemetery in Ur)

A tanbur is defined as "a long-necked stringed instrument with a small egg- or pear-shaped body, with an arched or round back, usually with a soundboard of wood or hide, and a long, straight neck". The tanbur probably developed from the bowl harp as the neck was straightened out to allow the string/s to be pressed down to create more notes. Tomb paintings and stone carvings in Egypt testify to the fact that harps and tanburs (together with flutes and percussion instruments) were being played in ensemble 3500 - 4000 years ago.

Egyptian wall painting, Thebes, 1420 BCE

Archaeologists have also found many similar relics in the ruins of the ancient Persian and Mesopotamian cultures. Many of these instruments have survived into modern times in almost unchanged form, as witness the folk instruments of the region like the Turkish saz, Balkan tamburitsa, Iranian setar, Afghan panchtar and Greek bouzouki.

The oldest preserved guitar-like instrument

At 3500 years old, this is the ultimate vintage guitar! It belonged to the Egyptian singer Har-Mose. He was buried with his tanbur close to the tomb of his employer, Sen-Mut, architect to Queen Hatshepsut, who was crowned in 1503 BCE. Sen-Mut (who, it is suspected, was far more than just chief minister and architect to the queen) built Hatshepsuts beautiful mortuary temple, which stands on the banks of the Nile to this day. 

Har-Moses instrument had three strings and a plectrum suspended from the neck by a cord. 

The soundbox was made of beautifully polished cedarwood and had a rawhide "soundboard". It can be seen today at the Archaeological Museum in Cairo.

 

Queen Hatshepsut

What is a guitar, anyway?

To distinguish guitars from other members of the tanbur family, we need to define what a guitar is. Dr. Kasha defines a guitar as having "a long, fretted neck, flat wooden soundboard, ribs, and a flat back, most often with incurved sides" .
The oldest known iconographical representation of an instrument displaying all the essential features of a guitar is a stone carving at Alaca Huyuk in Turkey, of a 3300 year old Hittite "guitar" with "a long fretted neck, flat top, probably flat back, and with strikingly incurved sides".

 

The Lute (Al'ud, Oud)

The Moors brought the oud to Spain. The tanbur had taken another line of development in the Arabian countries, changing in its proportions and remaining fretless. 
The Europeans added frets to the oud and called it a "lute" - this derives from the Arabic "Al'ud" (literally "the wood"), via the Spanish name "laud".
A lute or oud is defined as a "short-necked instrument with many strings, a large pear-shaped body with highly vaulted back, and an elaborate, sharply angled peghead".

Renaissance lute by Arthur Robb

It is hard to see how the guitar - with "a long, fretted neck, flat wooden soundboard, ribs, and a flat back, most often with incurved sides" - could possibly have evolved from the lute, with its "short neck with many strings, large pear-shaped body with highly vaulted back, and elaborate, sharply angled peghead".

The Guitar

The name "guitar" comes from the ancient Sanskrit word for "string" -"tar". (This is the language from which the languages of central Asia and northern India developed.) Many stringed folk instruments exist in Central Asia to this day which have been used in almost unchanged form for several thousand years, as shown by archeological finds in the area. Many have names that end in "tar", with a prefix indicating the number of strings:

Dotar

two = Sanskrit "dvi" - modern Persian "do" -
dotar, two-string instrument found in Turkestan

three = Sanskrit "tri" - modern Persian "se" -
setar, 3-string instrument, found in Persia (Iran),
(cf. sitar, India, elaborately developed, many-stringed)

four = Sanskrit "chatur" - modern Persian "char" -
chartar, 4-string instrument, Persia (most commonly known as "tar" in modern usage)
(cf. quitarra, early Spanish 4-string guitar,
modern Arabic qithara, Italian chitarra, etc)

five = Sanskrit "pancha" - modern Persian "panj" -
panchtar, 5 strings, Afghanistan

Indian Sitar

The Indian sitar almost certainly took its name from the Persian setar, but over the centuries the Indians developed it into a completely new instrument, following their own aesthetic and cultural ideals.

Persian Setar

Chartar ("Tar")

Tanburs and harps spread around the ancient world with travellers, merchants and seamen. The four-stringed Persian chartar (note the narrow waist!) arrived in Spain, where it changed somewhat in form and construction, acquired pairs of unison-tuned strings instead of single strings and became known as the quitarra or chitarra.

From four-, to five-, to six-string guitar

As we have seen, the guitar's ancestors came to Europe from Egypt and Mesopotamia. These early instruments had, most often, four strings - as we have seen above, the word "guitar" is derived from the Old Persian "chartar", which, in direct translation, means "four strings". Many such instruments, and variations with from three to five strings, can be seen in mediaeval illustrated manuscripts, and carved in stone in churches and cathedrals, from Roman times through till the Middle Ages. Right: Roman "guitar", c:a 200 CE.

Mediaeval psalter, c:a 900 CE. 

Angel with guitar, St. Stephen's church, 1591.

By the beginning of the Renaissance, the four-course (4 unison-tuned pairs of strings) guitar had become dominant, at least in most of Europe. (Sometimes a single first string was used.) The earliest known music for the four-course "chitarra" was written in 16th century Spain. The five-course guitarra battente (left) first appeared in Italy at around the same time, and gradually replaced the four-course instrument. The standard tuning had already settled at A, D, G, B, E, like the top five strings of the modern guitar.

In common with lutes, early guitars seldom had necks with more than 8 frets free of the body, but as the guitar evolved, this increased first to 10 and then to 12 frets to the body.

5-course guitar by Antonio Stradivarius, 1680

A sixth course of strings was added to the Italian "guitarra battente" in the 17th century, and guitar makers all over Europe followed the trend. The six-course arrangement gradually gave way to six single strings, and again it seems that the Italians were the driving force. (The six-string guitar can thus be said to be a development of the twelve-string, rather than vice versa, as is usually assumed.)

In the transition from five courses to six single strings, it seems that at least some existing five-course instruments were modified to the new stringing pattern. This was a fairly simple task, as it only entailed replacing (or re-working) the nut and bridge, and plugging four of the tuning peg holes. An incredibly ornate guitar by the German master from Hamburg, Joakim Thielke (1641 - 1719), was altered in this way. (Note that this instrument has only 8 frets free of the body.)

 

At the beginning of the 19th century one can see the modern guitar beginning to take shape. Bodies were still fairly small and narrow-waisted.

6-string guitar by George Louis Panormo, 1832

The modern "classical" guitar took its present form when the Spanish maker Antonio Torres increased the size of the body, altered its proportions, and introduced the revolutionary "fan" top bracing pattern, in around 1850. His design radically improved the volume, tone and projection of the instrument, and very soon became the accepted construction standard. It has remained essentially unchanged, and unchallenged, to this day.

Guitar by Antonio Torres Jurado, 1859 

Steel-string and electric guitars

At around the same time that Torres started making his breakthrough fan-braced guitars in Spain, German immigrants to the USA - among them Christian Fredrich Martin - had begun making guitars with X-braced tops. Steel strings first became widely available in around 1900. Steel strings offered the promise of much louder guitars, but the increased tension was too much for the Torres-style fan-braced top. A beefed-up X-brace proved equal to the job, and quickly became the industry standard for the flat-top steel string guitar.

At the end of the 19th century Orville Gibson was building archtop guitars with oval sound holes. He married the steel-string guitar with a body constructed more like a cello, where the bridge exerts no torque on the top, only pressure straight down. This allows the top to vibrate more freely, and thus produce more volume. In the early 1920's designer Lloyd Loar joined Gibson, and refined the archtop "jazz" guitar into its now familiar form with f-holes, floating bridge and cello-type tailpiece.

The electric guitar was born when pickups were added to Hawaiian and "jazz" guitars in the late 1920's, but met with little success before 1936, when Gibson introduced the ES150 model, which Charlie Christian made famous.

With the advent of amplification it became possible to do away with the soundbox altogether. In the late 1930's and early 1940's several actors were experimenting along these lines, and controversy still exists as to whether Les Paul, Leo Fender, Paul Bigsby or O.W. Appleton constructed the very first solid-body guitar. Be that as it may, the solid-body electric guitar was here to stay.

sources by: http://www.guyguitars.com/eng/handbook/BriefHistory.html

10 Health benefits of drinking tea

There are lots of reasons why I enjoy a hot cup of tea: I love the aroma of various flavors of tea; holding onto a hot tea mug warms my hands on a cold winter morning; sipping tea in front of the fireplace is a great way to relax. And those are just the feel-good reasons. If you're not drinking tea yet, read up on these 10 ways tea does your body good and then see if you're ready to change your Starbucks order!

1. Tea contains antioxidants. Like the Rust-Oleum paint that keeps your outdoor furniture from rusting, tea's antioxidants protect your body from the ravages of aging and the effects of pollution.

2. Tea has less caffeine than coffee. Coffee usually has two to three times the caffeine of tea (unless you're a fan of Morning Thunder, which combines caffeine with mate, an herb that acts like caffeine in our body). An eight-ounce cup of coffee contains around 135 mg caffeine; tea contains only 30 to 40 mg per cup. If drinking coffee gives you the jitters, causes indigestion or headaches or interferes with sleep -- switch to tea.

3. Tea may reduce your risk of heart attack and stroke. Unwanted blood clots formed from cholesterol and blood platelets cause heart attack and stroke. Drinking tea may help keep your arteries smooth and clog-free, the same way a drain keeps your bathroom pipes clear. A 5.6-year study from the Netherlands found a 70 percent lower risk of fatal heart attack in people who drank at least two to three cups of black tea daily compared to non-tea drinkers.

4. Tea protects your bones. It's not just the milk added to tea that builds strong bones. One study that compared tea drinkers with non-drinkers, found that people who drank tea for 10 or more years had the strongest bones, even after adjusting for age, body weight, exercise, smoking and other risk factors. The authors suggest that this may be the work of tea's many beneficial phytochemicals.

5. Tea gives you a sweet smile. One look at the grimy grin of Austin Powers and you may not think drinking tea is good for your teeth, but think again. It's the sugar added to it that's likely to blame for England's bad dental record. Tea itself actually contains fluoride and tannins that may keep plaque at bay. So add unsweetened tea drinking to your daily dental routine of brushing and flossing for healthier teeth and gums.

6. Tea bolsters your immune defenses. Drinking tea may help your body's immune system fight off infection. When 21 volunteers drank either five cups of tea or coffee each day for four weeks, researchers saw higher immune system activity in the blood of the tea drinkers.

7. Tea protects against cancer. Thank the polyphenols, the antioxidants found in tea, once again for their cancer-fighting effects. While the overall research is inconclusive, there are enough studies that show the potential protective effects of drinking tea to make adding tea to your list of daily beverages.

8. Tea helps keep you hydrated. Caffeinated beverages, including tea, used to be on the list of beverages thatdidn't contribute to our daily fluid needs. Since caffeine is a diuretic and makes us pee more, the thought was that caffeinated beverages couldn't contribute to our overall fluid requirement. However, recent research has shown that the caffeine really doesn't matter -- tea and other caffeinated beverages definitely contribute to our fluid needs. The only time the caffeine becomes a problem as far as fluid is concerned is when you drink more than five or six cups of a caffeinated beverage at one time.

9. Tea is calorie-free. Tea doesn't have any calories, unless you add sweetener or milk. Consuming even 250 fewer calories per day can result in losing one pound per week. If you're looking for a satisfying, calorie-free beverage, tea is a top choice.

10. Tea increases your metabolism. Lots of people complain about a slow metabolic rate and their inability to lose weight. Green tea has been shown to actually increase metabolic rate so that you can burn 70 to 80 additional calories by drinking just five cups of green tea per day. Over a year's time you could lose eight pounds just by drinking green tea. Of course, taking a 15-minute walk every day will also burn calories.

Dinosaur

Dinosaurs are a diverse group of animals of the clade Dinosauria . They first appeared during the Triassic period, approximately 230 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic (about 200 million years ago) until the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups at the close of the Mesozoic Era . The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic Period and, consequently, they are considered a subgroup of dinosaurs in most modern classification systems.  Some birds survived the extinction event that occurred 66 million years ago, and their descendants continue the dinosaur lineage to the present day.
Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 9,000 living species, are the most diverse group of vertebrates besides perciform fish.  Using fossil evidence, paleontologists have identified over 500 distinct genera  and more than 1,000 different species of non-avian dinosaurs. [ 6 ] Dinosaurs are represented on every continent by both extant species and fossil remains. Some are herbivorous, others carnivorous. Many dinosaurs (aside from the birds) have been bipedal , while many extinct groups included quadrupedal species, and some were able to shift between these body postures. Many species possess elaborate display structures such as horns or crests, and some prehistoric groups developed skeletal modifications such as bony armor and spines . Birds have been the planet's dominant flying vertebrate since the extinction of the pterosaurs , and evidence suggests that egg laying and nest building are traits shared by all dinosaurs. Many prehistoric dinosaurs were large animals—the largest sauropods may have achieved a length of 58 meters (190 feet) and a height of 9.25 meters (30 feet 4 inches) but the idea that non-avian dinosaurs were uniformly gigantic is a misconception based on preservation bias; large, sturdy bones are more likely to last until they are fossilized. Many dinosaurs were quite small; Xixianykus , for example, was only about 50 cm (20 in) long.
Although the word dinosaur means "terrible lizard", the name is somewhat misleading, as dinosaurs are not lizards . Rather, they represent a separate group of reptiles with a distinct upright posture not found in lizards, and many extinct forms did not exhibit traditional reptilian characteristics. Additionally, many prehistoric animals, including mosasaurs , ichthyosaurs , pterosaurs, plesiosaurs , and Dimetrodon , are popularly conceived of as dinosaurs, but are not classified as dinosaurs. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded . Most research conducted since the 1970s , however, has indicated that ancient dinosaurs, particularly the carnivorous groups, were active animals with elevated metabolisms and numerous adaptations for social interaction.
Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons have been major attractions at museums around the world, and dinosaurs have become an enduring part of world culture. The large sizes of some groups, as well as their seemingly monstrous and fantastic nature, have ensured dinosaurs' regular appearance in best-selling books and films, such as Jurassic Park . Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, and new discoveries are regularly covered by the media.

Etymology

The taxon Dinosauria was formally named in 1842 by paleontologist Sir Richard Owen , who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were then being recognized in England and around the world. The term is derived from the Greek words δεινός ( deinos , meaning "terrible," "potent," or "fearfully great") and σαῦρος ( sauros , meaning "lizard" or "reptile").  Though the taxonomic name has often been interpreted as a reference to dinosaurs' teeth, claws, and other fearsome characteristics, Owen intended it merely to evoke their size and majesty.
Definition
Under phylogenetic taxonomy, dinosaurs are usually defined as the group consisting of Triceratops , Neornithes [modern birds], their most recent common ancestor , and all descendants".  It has also been suggested that Dinosauria be defined with respect to the most recent common ancestor of Megalosaurus and Iguanodon , because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia ", encompassing theropods (mostly bipedal carnivores and birds ), ankylosaurians (armored herbivorous quadrupeds), stegosaurians (plated herbivorous quadrupeds), ceratopsians (herbivorous quadrupeds with horns and frills), ornithopods (bipedal or quadrupedal herbivores including "duck-bills"), and, perhaps, sauropodomorphs (mostly large herbivorous quadrupeds with long necks and tails).
Many paleontologists note that the point at which sauropodomorphs and theropods diverged may omit sauropodomorphs from the definition for both saurischians and dinosaurs. To avoid instability, Dinosauria can be more conservatively defined with respect to four anchoring nodes: Triceratops horridus , Saltasaurus loricatus , and Passer domesticus , their most recent common ancestor, and all descendants. This "safer" definition can be expressed as "Dinosauria = Ornithischia + Sauropodomorpha + Theropoda ".
There is near universal consensus among paleontologists that birds are the descendants of theropod dinosaurs. In traditional taxonomy, birds were considered a separate " class " that had evolved from dinosaurs. However, a majority of modern paleontologists reject the traditional style of classification in favor of phylogenetic nomenclature , which requires that all descendants of a single common ancestor must be included in a group for that group to be natural. Birds are thus considered by most modern scientists to be dinosaurs and dinosaurs are, therefore, not extinct. Birds are classified by most paleontologists as belonging to the subgroup Maniraptora , which are coelurosaurs , which are theropods, which are saurischians , which are dinosaurs.

Origins and early evolution

Dinosaurs diverged from their archosaur ancestors approximately 230 million years ago during the Middle to Late Triassic period, roughly 20 million years after the Permian–Triassic extinction event wiped out an estimated 95% of all life on Earth . Radiometric dating of the rock formation that contained fossils from the early dinosaur genus Eoraptor establishes its presence in the fossil record at this time. Paleontologists think that Eoraptor resembles the common ancestor of all dinosaurs;  if this is true, its traits suggest that the first dinosaurs were small, bipedal predators .  The discovery of primitive, dinosaur-like ornithodirans such as Marasuchus and Lagerpeton in Argentinian Middle Triassic strata supports this view; analysis of recovered fossils suggests that these animals were indeed small, bipedal predators. Dinosaurs may have appeared as early as 243 million years ago, as evidenced by remains of the genus Nyasasaurus from that period, though known fossils of these animals are too fragmentary to tell if they are dinosaurs or very close dinosaurian relatives.
When dinosaurs appeared, terrestrial habitats were occupied by various types of archosaurs and therapsids , such as aetosaurs , cynodonts , dicynodonts , ornithosuchids , rauisuchians , and rhynchosaurs . Most of these other animals became extinct in the Triassic, in one of two events. First, at about the boundary between the Carnian and Norian faunal stages (about 215 million years ago), dicynodonts and a variety of basal archosauromorphs , including the prolacertiforms and rhynchosaurs, became extinct. This was followed by the Triassic–Jurassic extinction event (about 200 million years ago), that saw the end of most of the other groups of early archosaurs, like aetosaurs, ornithosuchids, phytosaurs , and rauisuchians. These losses left behind a land fauna of crocodylomorphs , dinosaurs, mammals , pterosaurians , and turtles . The first few lines of early dinosaurs diversified through the Carnian and Norian stages of the Triassic, most likely by occupying the niches of the groups that became extinct.

Evolution and paleobiogeography

Dinosaur evolution after the Triassic follows changes in vegetation and the location of continents. In the Late Triassic and Early Jurassic, the continents were connected as the single landmass Pangaea , and there was a worldwide dinosaur fauna mostly composed of coelophysoid carnivores and early sauropodomorph herbivores . Gymnosperm plants (particularly conifers ), a potential food source, radiated in the Late Triassic. Early sauropodomorphs did not have sophisticated mechanisms for processing food in the mouth, and so must have employed other means of breaking down food farther along the digestive tract.  The general homogeneity of dinosaurian faunas continued into the Middle and Late Jurassic, where most localities had predators consisting of ceratosaurians , spinosauroids , and carnosaurians , and herbivores consisting of stegosaurian ornithischians and large sauropods. Examples of this include the Morrison Formation of North America and Tendaguru Beds of Tanzania. Dinosaurs in China show some differences, with specialized sinraptorid theropods and unusual, long-necked sauropods like Mamenchisaurus . Ankylosaurians and ornithopods were also becoming more common, but prosauropods had become extinct. Conifers and pteridophytes were the most common plants. Sauropods, like the earlier prosauropods, were not oral processors, but ornithischians were evolving various means of dealing with food in the mouth, including potential cheek -like organs to keep food in the mouth, and jaw motions to grind food.  Another notable evolutionary event of the Jurassic was the appearance of true birds, descended from maniraptoran coelurosaurians .
By the Early Cretaceous and the ongoing breakup of Pangaea, dinosaurs were becoming strongly differentiated by landmass. The earliest part of this time saw the spread of ankylosaurians, iguanodontians , and brachiosaurids through Europe, North America, and northern Africa. These were later supplemented or replaced in Africa by large spinosaurid and carcharodontosaurid theropods, and rebbachisaurid and titanosaurian sauropods, also found in South America. In Asia, maniraptoran coelurosaurians like dromaeosaurids , troodontids , and oviraptorosaurians became the common theropods, and ankylosaurids and early ceratopsians like Psittacosaurus became important herbivores. Meanwhile, Australia was home to a fauna of basal ankylosaurians, hypsilophodonts , and iguanodontians. The stegosaurians appear to have gone extinct at some point in the late Early Cretaceous or early Late Cretaceous. A major change in the Early Cretaceous, which would be amplified in the Late Cretaceous, was the evolution of flowering plants . At the same time, several groups of dinosaurian herbivores evolved more sophisticated ways to orally process food. Ceratopsians developed a method of slicing with teeth stacked on each other in batteries, and iguanodontians refined a method of grinding with tooth batteries, taken to its extreme in hadrosaurids . Some sauropods also evolved tooth batteries, best exemplified by the rebbachisaurid Nigersaurus .
There were three general dinosaur faunas in the Late Cretaceous. In the northern continents of North America and Asia, the major theropods were tyrannosaurids and various types of smaller maniraptoran theropods, with a predominantly ornithischian herbivore assemblage of hadrosaurids, ceratopsians, ankylosaurids, and pachycephalosaurians . In the southern continents that had made up the now-splitting Gondwana , abelisaurids were the common theropods, and titanosaurian sauropods the common herbivores. Finally, in Europe, dromaeosaurids, rhabdodontid iguanodontians, nodosaurid ankylosaurians, and titanosaurian sauropods were prevalent. Flowering plants were greatly radiating, with the first grasses appearing by the end of the Cretaceous. Grinding hadrosaurids and shearing ceratopsians became extremely diverse across North America and Asia. Theropods were also radiating as herbivores or omnivores , with therizinosaurians and ornithomimosaurians becoming common.
The Cretaceous–Paleogene extinction event , which occurred approximately 66 million years ago at the end of the Cretaceous period, caused the extinction of all dinosaur groups except for the neornithine birds. Some other diapsid groups, such as crocodilians, sebecosuchians , turtles , lizards , snakes , sphenodontians , and choristoderans , also survived the event.
The surviving lineages of neornithine birds, including the ancestors of modern ratites , ducks and chickens , and a variety of waterbirds , diversified rapidly at the beginning of the Paleogene period, entering ecological niches left vacant by the extinction of Mesozoic dinosaur groups such as the arboreal enantiornithines , aquatic hesperornithines , and even the larger terrestrial theropods (in the form of Gastornis , mihirungs , and " terror birds "). However, mammals were also rapidly diversifying during this time, and out-competed the neornithines for dominance of most terrestrial niches

Classification

Dinosaurs are archosaurs , like modern crocodilians . Within the archosaur group, dinosaurs are differentiated most noticeably by their gait. Dinosaur legs extend directly beneath the body, whereas the legs of lizards and crocodilians sprawl out to either side.
Collectively, dinosaurs as a clade are divided into two primary branches, Saurischia and Ornithischia . Saurischia includes those taxa sharing a more recent common ancestor with birds than with Ornithischia , while Ornithischia includes all taxa sharing a more recent common ancestor with Triceratops than with Saurischia. Anatomically, these two groups can be distinguished most noticeably by their pelvic structure. Early saurischians—"lizard-hipped", from the Greek sauros (σαῦρος) meaning "lizard" and ischion (ἰσχίον) meaning "hip joint—retained the hip structure of their ancestors, with a pubis bone directed cranially , or forward. This basic form was modified by rotating the pubis backward to varying degrees in several groups ( Herrerasaurus ,  therizinosauroids , dromaeosaurids ,  and birds  ). Saurischia includes the theropods (exclusively bipedal and with a wide variety of diets) and sauropodomorphs (long-necked herbivores which include advanced, quadrupedal groups).
By contrast, ornithischians—"bird-hipped", from the Greek ornitheios (ὀρνίθειος) meaning "of a bird" and ischion (ἰσχίον) meaning "hip joint"—had a pelvis that superficially resembled a bird's pelvis: the pubis bone was oriented caudally (rear-pointing). Unlike birds, the ornithischian pubis also usually had an additional forward-pointing process. Ornithischia includes a variety of species which were primarily herbivores. ( NB: the terms "lizard hip" and "bird hip" are misnomers – birds evolved from dinosaurs with "lizard hips".)