Posts Tagged ‘twentieth century’
May 22nd, 2009 | 
Author: Diamonds have been found in numerous various locales but in only a select few in prominent amounts. Most frequently the diamond was discovered in the sand and gravel of stream beds, where it was conserved because of its immobile chemical nature, its incredible hardness, and its moderately high, precise gravity. In South Africa, other countries on the continent of Africa, and in Arkansas, diamonds were discovered in a changed peridotite know as “kimberlite.”
The four countries that initially provided the majority of the earth’s production of EGL loose diamonds, best value diamonds, and GIA diamond rings were India, Brazil, South Africa, and the Belgian Congo. The imperative fields of India were found in the eastern and southern areas of the peninsula; however most of the renowned mines were eventually abandoned.
Only a few hundred carats annually were produced from the gravels in the early twentieth century in comparison to a period of 2000 years where over 20,000,000 carats were produced per year. Until the eighteenth century, India was the only resource of diamonds and several of the celebrated gems were found there. Diamonds were found in Brazil in between 1700 and 1750 and continued to be mined there for decades and decades to come. The production became relatively smaller by the beginning of the twentieth century, with only about 250,000 carats per year.
Diamonds were discovered in the stream gravels in a variety of different districts, the most imperative located in the provinces of Minas Geraes and Bahia. The city of Diamantina, Minas Geraes, was positioned in the middle of the most industrious field, the diamonds being found primarily in the gravel and sand of the Rio Jequitinhonha and Rio Doce. Widespread upland deposits of diamond-bearing sands, clays, and gravels were also mined.
The black “carbonado” came solely from Bahia up until the early twentieth century when it was eventually discovered in the Central African Republic and other areas of Brazil. This particular type of diamond was difficult to classify as a non conflict diamond until recently, due to the diamond’s rarity. About 95 percent of the world’s production of diamonds came from Africa at the turn of the nineteenth century. The Belgian Congo was largest producer by leaps and bounds, supplying from placer deposits over 50 percent of the earth’s stockpile.
These Congo diamonds were largely of industrial grade and signified only about 13 percent of the overall value of diamonds found. The principal African diamonds were found in 1867 in the sand and gravels of the Vaal River in South Africa. In 1871 diamonds were discovered imbedded in the rock of many volcanic necks or pipes near the city of Kimberley in Griqualand-West, south of the Vaal River, close to the boundary of the Orange Free State (which eventually became a part of the Union of South Africa). The diamonds in this area were originally discovered in the soil consequential of the breakdown of the original distorted peridotite.
The soil was yellow in color due to iron oxides and was referred to as “yellow ground.” The initial mines in close proximity to the town of Kimberley were the Kimberley, Du Toitspan, De Beers, Wesselton, and Bultfontien. The Kimberley mine was dug to a depth of 3,500 feet before it was abandoned. The mines were primarily worked as open pits, but as they grew in depth, underground techniques to find quality diamonds that would pass any IGI appraisals for diamond jewelry were implemented.
The early system of treatment was to pound the blue ground into coarse remains and spread it out on platforms to fragment progressively under atmospheric persuasions. The process ultimately evolved into crushing the rock finely enough to allow instant concentration. The diamonds were lastly separated on shaking tables that were covered with grease—the diamonds stuck while the remaining materials were washed away.
Allison Ryan is a freelance marketing writer from San Diego, CA. She specializes in the history of the non conflict diamond and where to find best value diamonds. For GIA diamond rings or to design your own diamond jewelry, stop by http://www.diamondwave.com/.
Article Source: The Early History of the Diamond
The way a computer deals with time is totally different to the ways humans perceive it. We arrange time into seconds, minutes, hours, days, weeks, months and years, while computers on the other hand arrange time as a single number representing the seconds that have passed from a single point in time, known as the prime epoch.
Most computers use NTP (Network Time Protocol) to deal with time and on networks many are synchronised using a dedicated NTP time server. NTP knows nothing about days, years or centuries, only the seconds from the prime epoch. This prime epoch is set (for most systems) at midnight at the turn of the century twentieth century that for a human would be recorded as something like: 00:00 – 01,01,1900.
Computers, however, count time as the number of seconds past this point. If a computer was around in 1900 its timestamp on midnight January 1 would be 0 while in 1972 at the same date the timestamp would be 2,272,060,800, which represents the number of seconds since 1900.
The timestamps restart every 136 years with the next wrap around due in 2036, this has caused uneasiness amongst some who fear a Millennium Bug type scenario, although most doubt such events would occur, however, when a wrap-around of the timestamp does happen an era integer will be added (+1), to allow computers to deal with time spans that cover more than one wrap-around. If computers and NTP need to deal with time that spans before the prime epoch a negative integer is used (for the year 1500 a -3 will be used to represent three cycles of 136 years).
Timestamps are used in virtually every transaction that modern computers are tasked to do such as sending emails, debugging and programming. Because time is linear, a computer knows that each timestamp is always greater than the previous one and therefore computers and NTP find it difficult to deal with inaccuracies in time, particularly when time suddenly appears to go backwards.
This can happen if computers are not synchronised to the same time. If an email is sent to a machine with a slower clock, it appears to the computer to have been received before it has been sent. Lack of synchronisation can serious problems and can even leave a system vulnerable to malicious attacks and even fraud.
Because of this, most computer networks are synchronised to UTC (Coordinated Universal Time). UTC is a global timescale and the same for everybody worldwide it is based on the time told by atomic clocks which are highly accurate, neither gaining nor losing a second in millions of years.
Most computer networks use a dedicated NTP time server to receive a UTC time to synchronise their computers too. UTC is available from across the Internet (although unsecured), via the GPS network (Global Positioning System), or by receiving national time and frequency broadcasts via long wave.
NTP synchronises a computer by checking the received UTC time and adding to or holding a computer’s timestamp until it perfectly matches UTC. By using a dedicated NTP time server UTC can be maintained on a network to a few milliseconds of UTC time.
Richard N Williams is a technical author and specialist in atomic clocks, telecommunications, NTP and network time synchronisation helping to develop dedicated NTP clocks. Please visit us for more information about a network time server or other NTP server solutions.
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Article Source: NTP – Understanding Computer Timestamps