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            <P align=center><B><FONT face="Arial Rounded MT Bold" size=6><FONT 
            color=#660033>The History of 
            Time-Keeping<BR></FONT><BR></FONT></B><IMG border=0 height=257 
            src="Cesium-atomic-clock_files/earlywaterclok.jpe" width=360><FONT 
            size=3><BR><BR><BR>In respect to human history, time keeping is a 
            relatively recent desire ? probably 5000 to 6000 years old.<SPAN 
            style="mso-spacerun: yes"> </SPAN>It was most likely initiated in 
            the Middle East and North Africa.</FONT></P>
            <P><FONT size=3>A clock is defined as a device that consists of two 
            qualities:</FONT></P>
            <UL type=disc>
              <LI class=MsoNormal 
              style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l1 level1 lfo1; tab-stops: list .5in"><FONT 
              size=3><I>A regular, constant or repetitive process or action to 
              mark off equal increments of time</I>. Early examples of such 
              processes included movement of the sun across the sky, candles 
              marked in increments, oil lamps with marked reservoirs, sand 
              glasses ("hourglasses"), and in the Orient, small stone or metal 
              mazes filled with incense that would burn at a certain pace.<BR 
              style="mso-special-character: line-break"></FONT>
              <LI class=MsoNormal 
              style="mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l1 level1 lfo1; tab-stops: list .5in"><FONT 
              size=3><I>A means of keeping track of the increments of time and 
              displaying the result</I>.</FONT> </LI></UL>
            <H2><SPAN 
            style="COLOR: black; FONT-WEIGHT: normal; mso-bidi-font-size: 18.0pt"><FONT 
            size=3>Relaying the history of time measurement has a degree of 
            inaccuracy, much like clocks themselves.<SPAN 
            style="mso-spacerun: yes"> </SPAN>What follows is, if not completely 
            accurate, as close as many researchers can ascertain. 
            <O:P></O:P></FONT></SPAN></H2>
            <P>&nbsp;</P></TD>
          <TD height=749 width="30%">
            <P align=center><B><FONT color=#800000 
            size=4><BR><BR>Contents</FONT></B></P>
            <P align=center><SPAN style="BACKGROUND-COLOR: #ffffff"><FONT 
            color=#800000><A 
            href="http://www.beaglesoft.com/timekeepinghistory2.htm#Using the Sun">Keeping 
            time with the Sun</A></FONT></SPAN></P>
            <P align=center><SPAN style="BACKGROUND-COLOR: #ffffff"><FONT 
            color=#800000><A 
            href="http://www.beaglesoft.com/timekeepinghistory2.htm#Using Stars">Keeping 
            time with the Stars</A></FONT></SPAN></P>
            <P align=center><SPAN style="BACKGROUND-COLOR: #ffffff"><FONT 
            color=#800000><A 
            href="http://www.beaglesoft.com/timekeepinghistory2.htm#Using Water">Keeping 
            time with Water</A></FONT></SPAN></P>
            <P align=center><SPAN style="BACKGROUND-COLOR: #ffffff"><FONT 
            color=#800000><A 
            href="http://www.beaglesoft.com/timekeepinghistory2.htm#Mechanical Clocks">Mechanical 
            Time</A></FONT></SPAN></P>
            <P align=center><SPAN style="BACKGROUND-COLOR: #ffffff"><FONT 
            color=#800000><A 
            href="http://www.beaglesoft.com/timekeepinghistory2.htm#Quartz Clocks">Quartz 
            Clocks</A></FONT></SPAN></P>
            <P align=center><SPAN style="BACKGROUND-COLOR: #ffffff"><FONT 
            color=#800000><A 
            href="http://www.beaglesoft.com/timekeepinghistory2.htm#Atomic Clocks">Atomic 
            Clocks</A><BR><BR><A 
            href="http://www.beaglesoft.com/timekeepinghistory2.htm#Links to Clock, Watch, Time and Horology Websites">Links 
            to Horology 
            Sites<BR><BR><BR><BR><BR><BR><BR><BR><BR><BR><BR><BR><BR><BR><BR></A></FONT></SPAN></P></TD></TR>
        <TR>
          <TD height=1034 width="70%">
            <H2><SPAN 
            style="COLOR: black; FONT-WEIGHT: normal; mso-bidi-font-size: 18.0pt"><FONT 
            size=3></O:P></FONT></SPAN></H2>
            <H2 align=center style="TEXT-ALIGN: center"><FONT size=4><SPAN 
            style="COLOR: black; mso-bidi-font-size: 18.0pt"><I><O:P></I></SPAN><SPAN 
            style="mso-bidi-font-size: 18.0pt"><FONT color=#800000><A 
            name="Using the Sun">Using the 
            Sun</A>&nbsp;<BR></FONT></SPAN></FONT><IMG border=0 height=96 
            src="Cesium-atomic-clock_files/sun123.gif" width=97><SPAN 
            style="COLOR: black; mso-bidi-font-size: 18.0pt"><FONT size=3></O:P> 
            </FONT></SPAN></H2>
            <H2><SPAN 
            style="COLOR: black; FONT-WEIGHT: normal; mso-bidi-font-size: 18.0pt"><FONT 
            size=3>The Egyptians are the first group of people that we can 
            reasonably prove that took time-keeping seriously as a culture.<SPAN 
            style="mso-spacerun: yes"> </SPAN>Many believe that the Sumerians 
            were thousands of years ahead of the game, but proof of this is only 
            speculative.<SPAN style="mso-spacerun: yes">&nbsp; 
            </SPAN><O:P></O:P></FONT></SPAN></H2>
            <P><FONT size=3>Around 3500 B.C. the Egyptians built ?Obelisks? -- 
            tall four-sided tapered monuments -- and placed them in strategic 
            locations to cast shadows from the sun. <SPAN 
            style="mso-bidi-font-size: 10.0pt">Their moving shadows formed a 
            kind of sundial, enabling citizens to partition the day into two 
            parts by indicating noon. They also showed the year's longest and 
            shortest days when the shadow at noon was the shortest or longest of 
            the year. Later, markers added around the base of the monument would 
            indicate further time subdivisions. 
            </SPAN><B><O:P></O:P></B></FONT></P>
            <H2><SPAN 
            style="COLOR: black; FONT-WEIGHT: normal; mso-bidi-font-size: 18.0pt"><FONT 
            size=3>Around 1500 B.C., the Egyptians took the next step forward 
            with a more accurate ?shadow clock? or ?sundial.?<SPAN 
            style="mso-spacerun: yes"> </SPAN>The sundial was divided into 10 
            parts, with two ?twilight? hours indicated.<SPAN 
            style="mso-spacerun: yes"> </SPAN>This sundial only kept accurate 
            time (in relative terms) for a half day.<SPAN 
            style="mso-spacerun: yes"> </SPAN>So at midday, the device had to be 
            turned 180 degrees to measure the afternoon hours.<O:P> 
            </O:P></FONT></SPAN></H2>
            <P><FONT size=3>A sundial tracks the apparent movement of the sun 
            around the earth's celestial pole by casting a shadow (or point of 
            light) onto a surface that is marked by hour and minute lines. That 
            is why the shadow-casting object (the gnomon or style) must point 
            towards the north celestial pole, which is very near Polaris, the 
            North Star. The gnomon serves as an axis about which the sun appears 
            to rotate.</FONT></P>
            <P><FONT size=3>The sharper the shadow line is, the greater the 
            accuracy. So, generally speaking, the larger the sundial the greater 
            the accuracy, because the hour line can be divided into smaller 
            portions of time. But if a sundial gets too large, a point of 
            diminishing returns is reached because, due to the diffraction of 
            light waves and the width of the sun's face, the shadow spreads out 
            and becomes fuzzy, making the dial difficult to read.</FONT></P>
            <P><B><FONT size=3>I</FONT></B><FONT size=3>n the quest for more 
            year-round accuracy, sundials evolved from flat horizontal or 
            vertical plates to more elaborate forms. One version was the 
            hemispherical dial, a bowl-shaped depression cut into a block of 
            stone, carrying a central vertical gnomon (pointer) and scribed with 
            sets of hour lines for different seasons. The hemicycle, thought to 
            have been invented about 300 B.C., removed the useless half of the 
            hemisphere to give an appearance of a half-bowl cut into the edge of 
            a squared block. <B><SPAN 
            style="COLOR: black"><O:P></O:P></SPAN></B></FONT></P>
            <H2 align=center style="TEXT-ALIGN: center">&nbsp;</H2>
            <P>&nbsp;</P></TD>
          <TD height=1034 width="30%">
            <P align=center><BR><BR><BR><BR><BR><BR><BR><BR><BR><BR><IMG 
            border=0 height=260 src="Cesium-atomic-clock_files/obelisk1.jpe" 
            width=150><BR><FONT face=Arial size=1><FONT 
            color=#800000>Obelisk</FONT><BR><BR><BR><IMG border=0 height=148 
            src="Cesium-atomic-clock_files/srno3121.jpe" width=147><BR><FONT 
            color=#800000>Copper Sundial</FONT></FONT></P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P></TD></TR>
        <TR>
          <TD height=429 width="70%">
            <H2 align=center style="TEXT-ALIGN: center"><BR><FONT color=#800000 
            size=4><SPAN style="mso-bidi-font-size: 18.0pt"><A 
            name="Using Stars">Using Stars<O:P> </A>&nbsp;</SPAN></FONT></H2>
            <DIV align=center>
            <CENTER>
            <TABLE border=0 width="50%">
              <TBODY>
              <TR>
                <TD align=right width="52%">
                  <P align=center><IMG align=right border=0 height=147 
                  src="Cesium-atomic-clock_files/wizard.gif" width=144></P></TD>
                <TD bgColor=#000000 width="48%"><FONT color=#000000><IMG 
                  border=0 height=167 
                  src="Cesium-atomic-clock_files/twinkling_stars.gif" 
                  width=68><IMG border=0 height=167 
                  src="Cesium-atomic-clock_files/twinkling_stars.gif" 
                  width=68></FONT></TD></TR></TBODY></TABLE></CENTER></DIV>
            <H2><SPAN 
            style="COLOR: black; FONT-WEIGHT: normal; mso-bidi-font-size: 18.0pt"><FONT 
            size=3>The Egyptians improved upon the sundial with a ?merkhet,? the 
            oldest known astronomical tool.<SPAN style="mso-spacerun: yes"> 
            </SPAN>It was developed around 600 B.C. and uses a string with a 
            weight on the end to accurately measure a straight vertical line 
            (much like a carpenter uses a plumb bob today). A pair of merkhets 
            were used to establish a North-South line by lining them up with the 
            Pole Star.<SPAN style="mso-spacerun: yes"> </SPAN>This allowed for 
            the measurement of nighttime hours as it measured when certain stars 
            crossed a marked meridian on the sundial.<SPAN 
            style="mso-spacerun: yes">&nbsp; 
            </SPAN><O:P></O:P></FONT></SPAN></H2>
            <H2><SPAN 
            style="COLOR: black; FONT-WEIGHT: normal; mso-bidi-font-size: 18.0pt"><FONT 
            size=3>By 30 B.C., there were as many as 13 different types of 
            sundials used across Greece, Asia Minor and Italy.<O:P> 
            </O:P></FONT></SPAN></H2>
            <P>&nbsp;</P></TD>
          <TD height=429 width="30%">
            <P align=center><BR><BR><BR><BR><BR><BR><IMG border=0 height=267 
            src="Cesium-atomic-clock_files/merkhet1.jpe" width=158><BR><FONT 
            color=#800000 face=Arial size=1>Merkhet</FONT></P></TD></TR>
        <TR>
          <TD height=1444 width="70%">
            <P align=center style="TEXT-ALIGN: center"><B><FONT color=#800000 
            size=4><A name="Using Water">Using Water<O:P> 
            </A>&nbsp;<BR></FONT></B><IMG border=0 height=82 
            src="Cesium-atomic-clock_files/cloud1.gif" width=103></P>
            <P><SPAN style="COLOR: black"><FONT size=3>?Clepsydras? or Water 
            Clocks were among the first time-keeping devices that didn?t use the 
            sun or the passage of celestial bodies to calculate time.<SPAN 
            style="mso-spacerun: yes"> </SPAN></FONT></SPAN><FONT size=3>One of 
            the oldest was found in the tomb of ancient Egyptian King 
            Amenhotep&nbsp;I, buried around 1500&nbsp;B.C.</FONT></P>
            <P><SPAN style="COLOR: black"><FONT size=3>Around 325 B.C. the 
            Greeks began using clepsydras (Greek for "water thief") by the 
            regular dripping of water through a narrow opening and accumulating 
            the water in a reservoir where a float carrying a pointer rose and 
            marked the hours.<SPAN style="mso-spacerun: yes"> </SPAN>A slightly 
            different water clock released water at a regulated rate into a bowl 
            until it sank.<SPAN style="mso-spacerun: yes"> </SPAN>These clocks 
            were common across the Middle East, and were still being used in 
            parts of Africa during the early 20<SUP>th</SUP> century.<SPAN 
            style="mso-spacerun: yes"> </SPAN>They could not be relied on to 
            tell time more closely than a fairly large fraction of an hour.<SPAN 
            style="mso-spacerun: yes">&nbsp; 
</SPAN><O:P></O:P></FONT></SPAN></P>
            <P><FONT size=3><BR>More elaborate and impressive mechanized water 
            clocks were developed between 100&nbsp;B.C. and 500&nbsp;A.D. by 
            Greek and Roman horologists and astronomers. The added complexity 
            was aimed at making the flow more constant by regulating the 
            pressure, and at providing fancier displays of the passage of time. 
            Some water clocks rang bells and gongs; others opened doors and 
            windows to show little figures of people, or moved pointers, dials, 
            and astrological models of the universe.</FONT></P>
            <P><FONT size=3>A Greek astronomer, Andronikos, supervised the 
            construction of the Tower of the Winds in Athens in the 1st century 
            B.C. This octagonal structure showed scholars and marketplace 
            shoppers both sundials and mechanical hour indicators. It featured a 
            24-hour mechanized clepsydra and indicators for the eight winds from 
            which the tower got its name, and it displayed the seasons of the 
            year and astrological dates and periods.&nbsp;</FONT></P>
            <P>&nbsp;</P>
            <P><FONT size=3>In the Far East, mechanized 
            astronomical/astrological clock-making developed from 200 to 
            1300&nbsp;A.D. Third-century Chinese clepsydras drove various 
            mechanisms that illustrated astronomical phenomena. One of the most 
            elaborate clock towers was built by Su&nbsp;Sung and his associates 
            in 1088&nbsp;A.D. Su&nbsp;Sung's mechanism incorporated a 
            water-driven escapement invented about 725&nbsp;A.D.<SPAN 
            style="mso-spacerun: yes">&nbsp; </SPAN><SPAN 
            style="FONT-FAMILY: Georgia"><O:P></SPAN></FONT><SPAN 
            style="FONT-FAMILY: Georgia"><FONT size=3></O:P></FONT></SPAN></P>
            <P><FONT size=3>The Su&nbsp;Sung clock tower, over 30&nbsp;feet 
            tall, possessed a bronze power-driven armillary sphere for 
            observations, an automatically rotating celestial globe, and five 
            front panels with doors that permitted the viewing of mannequins 
            which rang bells or gongs, and held tablets indicating the hour or 
            other special times of the day. <SPAN 
            style="COLOR: black"><O:P>&nbsp; </SPAN></FONT></P>
            <P align=center><FONT face=Arial size=1><BR><IMG border=0 height=341 
            src="Cesium-atomic-clock_files/clock4.gif" width=350><BR>Su Sung's 
            clock tower, ca. 1088 </FONT></P>
            <P align=center>&nbsp;</P></TD>
          <TD height=1444 width="30%">
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center><BR><BR><BR><BR><IMG border=0 height=255 
            src="Cesium-atomic-clock_files/waterclock2.jpe" width=150><BR><FONT 
            color=#800000 face=Arial size=1>Water Clock</FONT><BR></P>
            <P align=center><IMG border=0 height=252 
            src="Cesium-atomic-clock_files/towerofthewinds.gif" 
            width=175><BR><FONT color=#800000>Tower of the Winds, Athens, 
            Greece</FONT> </P>
            <P align=center><FONT color=#800000><A name=A0032850><B><FONT 
            size=1>es?cape?ment</FONT></B></A><FONT size=1> (<IMG 
            align=absBottom height=15 src="Cesium-atomic-clock_files/ibreve.gif" 
            width=7>-sk<IMG align=absBottom height=15 
            src="Cesium-atomic-clock_files/amacr.gif" width=7>p<IMG 
            align=absBottom height=22 src="Cesium-atomic-clock_files/prime.gif" 
            width=4>m<IMG align=absBottom height=15 
            src="Cesium-atomic-clock_files/schwa.gif" width=6>nt)<BR><I>n.</I>A 
            mechanism consisting in general of an escape wheel and an anchor, 
            used especially in timepieces to control movement of the wheel and 
            to provide periodic energy impulses to a pendulum or 
            balance.</FONT></FONT> 
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
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          <TD height=1912 width="70%">
            <P>&nbsp;</P>
            <P align=center style="TEXT-ALIGN: center"><B><FONT color=#800000 
            size=4><A name="Mechanical Clocks">Mechanical Clocks<O:P> 
            </A>&nbsp;<BR><IMG border=0 height=171 
            src="Cesium-atomic-clock_files/gears.gif" width=99></FONT></B></P>
            <P><SPAN style="COLOR: black"><FONT size=3>The mechanical clock was 
            probably invented in medieval Europe.<SPAN 
            style="mso-spacerun: yes"> </SPAN>Clever arrangements of gears and 
            wheels were devised that turned by weights attached to them. As the 
            weights were pulled downward by the force of gravity, the wheels 
            were forced to turn in a slow, regular manner. A pointer, properly 
            attached to the wheels, marked the hours.<O:P> 
            </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>These clocks became 
            common in churches and monasteries and could be relied upon to tell 
            when to toll the bells for regular prayers or church attendance. 
            (The very word "clock" is from the French <I>cloche,</I> meaning 
            "bell.")<O:P> </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>Eventually, mechanical 
            clocks were designed to strike the hour and even to chime the 
            quarter-hour. However, they had only an hour hand and were not 
            enclosed. Even the best such clocks would gain or lose up to half an 
            hour a day.<O:P> </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>A technological advance 
            came with the invention of the ?spring-powered clock? around 
            1500-1510, credited to Peter Henlein of Nuremberg, Germany.<SPAN 
            style="mso-spacerun: yes"> </SPAN>Because these clocks could fit on 
            a mantle or shelf they became very popular among the rich.<SPAN 
            style="mso-spacerun: yes"> </SPAN>They did have some time-keeping 
            problems, though, as the clock slowed down as the mainspring 
            unwound. The development of the spring-powered clock was the 
            precursor to accurate time keeping. <O:P></O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>In 1582, Italian 
            scientist Galileo, then a teenager, had noticed the swaying 
            chandeliers in a cathedral. It seemed to him that the movement back 
            and forth was always the same whether the swing was a large one or a 
            small one. He timed the swaying with his pulse and then began 
            experimented with swinging weights. He found that the "pendulum" was 
            a way of marking off small intervals of time accurately.<O:P> 
            </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>Once Galileo had made the 
            discovery, the regular beat of the pendulum became the most accurate 
            source used to regulate the movement of the wheels and gears of a 
            clock.<O:P> </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>It wasn't a perfect 
            system, though, as a pendulum swings through the arc of a circle, 
            and when that is so, the time of the swing varies slightly with its 
            size. To make the pendulum keep truly accurate time, it must be made 
            to swing through a curve known as a "cycloid." 
            <O:P></O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>In 1656 Dutch astronomer 
            Christian Huygens first devised a successful pendulum clock.<SPAN 
            style="mso-spacerun: yes"> </SPAN>He used short pendulums that beat 
            several times a second, encased the works in wood, and hung the 
            clock on the wall.<SPAN style="mso-spacerun: yes"> </SPAN>It had an 
            error of less than one minute a day.<SPAN style="mso-spacerun: yes"> 
            </SPAN>This was a huge improvement on earlier mechanical clocks, and 
            subsequent refinements reduced the margin of error to less than 10 
            seconds per day.<O:P> </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>In 1670 English 
            clockmaker William Clement made use of a pendulum about a yard long 
            that took a full second to move back and forth, allowing greater 
            accuracy than ever before. He encased the pendulum and weights in 
            wood in order to diminish the effect of air currents, thus was born 
            the "grandfather's clock." For the first time, it made sense to add 
            a minute hand to the dial, since it was now possible to measure time 
            to the nearest second. <O:P></O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>In 1721George Graham 
            improved the pendulum clock?s accuracy to within a second a day by 
            compensating for changes in the pendulum's length caused by 
            temperature variations. The mechanical clock continued to develop 
            until it achieved an accuracy of a hundredth-of-a-second a day and 
            it became the accepted standard in most astronomical observatories. 
            <STRONG><SPAN 
            style="FONT-WEIGHT: normal"><O:P></O:P></SPAN></STRONG></FONT></SPAN></P>
            <H2 align=center style="TEXT-ALIGN: center"><IMG border=0 height=300 
            src="Cesium-atomic-clock_files/wallclock1870s.jpe" 
            width=112><BR><FONT face=Arial size=1>Wall Clock from the 
            1870s</FONT></H2>
            <P>&nbsp;</P></TD>
          <TD height=1912 width="30%">
            <P align=center><BR><BR><BR><BR><BR><IMG border=0 height=281 
            src="Cesium-atomic-clock_files/folver.jpe" width=164><BR><FONT 
            color=#800000 face=Arial size=1>early mechanical 
            clock</FONT><BR><BR><BR><BR><BR></P>
            <P align=center><BR><BR><BR><BR>&nbsp;&nbsp;&nbsp; <IMG border=0 
            height=205 src="Cesium-atomic-clock_files/galileo1.jpe" 
            width=156><BR><FONT face=Arial size=1><FONT 
            color=#800000>Galileo</FONT><BR><BR><BR><BR><IMG border=0 height=220 
            src="Cesium-atomic-clock_files/huygens.jpe" width=155><BR><FONT 
            color=#800000>Christian Huygens</FONT><BR><BR><BR><IMG border=0 
            height=150 src="Cesium-atomic-clock_files/graham.jpe" 
            width=136><BR><FONT color=#800000>George Graham</FONT></FONT></P>
            <P align=center><IMG border=0 height=161 
            src="Cesium-atomic-clock_files/grahamclock_popup.jpe" 
            width=145><BR><FONT color=#800000 face=Arial size=1>Early Graham 
            clock</FONT><BR></P>
            <P align=center>&nbsp;</P>
            <P align=center><BR><IMG border=0 height=178 
            src="Cesium-atomic-clock_files/17thcenturyclock.jpe" 
            width=144><BR><FONT color=#800000 face=Arial size=1>17th Century 
            Pocket Watch</FONT></P></TD></TR>
        <TR>
          <TD height=1344 width="70%">
            <H2 align=center style="TEXT-ALIGN: center"><SPAN 
            style="mso-bidi-font-size: 18.0pt"><FONT color=#800000 size=4><A 
            name="Quartz Clocks">Quartz Clocks<O:P> </A>&nbsp;<BR><IMG height=98 
            src="Cesium-atomic-clock_files/quartz.jpe" 
            width=129><BR></FONT><FONT color=#000000 face=Arial size=1>a quartz 
            crystal<BR>chemical name: SiO2 , Silicon dioxide</FONT></SPAN><SPAN 
            style="COLOR: black; mso-bidi-font-size: 18.0pt"><FONT size=3></O:P> 
            </FONT></SPAN></H2>
            <P class=MsoNormal><STRONG><SPAN 
            style="COLOR: black; FONT-WEIGHT: normal"><FONT size=3>The running 
            of a Quartz clock is based on an electric property of the quartz 
            crystal. When an electric field is applied to a quartz crystal, it 
            changes the shape of the crystal itself. If you then squeeze it or 
            bend it, an electric field is generated. When placed in an 
            electronic circuit, the interaction between the mechanical stress 
            and the electrical field causes the crystal to vibrate, generating a 
            constant electric signal which can then be used to measure time. 
            <O:P></O:P></FONT></SPAN></STRONG></P>
            <P><SPAN style="COLOR: black"><FONT size=3>Quartz clocks continue to 
            dominate the market because of the accuracy and reliability of their 
            performance and by their low cost when produced in mass quantities. 
            <O:P></O:P></FONT></SPAN></P>
            <H2 align=center style="TEXT-ALIGN: center"><SPAN 
            style="COLOR: black; mso-bidi-font-size: 18.0pt"><FONT 
            size=3>&nbsp;<O:P> <IMG border=0 height=136 
            src="Cesium-atomic-clock_files/timex.jpe" width=410><BR></FONT><FONT 
            face=Arial size=1>A modern quartz digital watch that not only keeps 
            accurate time,&nbsp;<BR>but can check your heart rate, 
            too.</FONT></SPAN></H2>
            <H2 align=center style="TEXT-ALIGN: center">&nbsp;</H2>
            <P align=center style="TEXT-ALIGN: center">&nbsp;</P>
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            <P>&nbsp;</P></TD>
          <TD height=1344 width="30%">
            <P align=center><BR><BR><BR><BR><BR>&nbsp; <IMG border=0 height=203 
            src="Cesium-atomic-clock_files/blackwatch.jpe" width=123><BR><FONT 
            color=#800000 face=Arial size=1>"The Black Watch", released in 1975 
            by the Sinclair Co., was one of the first digital watches ever 
            produced, and probably the worst.&nbsp; If you were unlucky enough 
            to buy one of these lemons you could expect various kinds of 
            trouble: </FONT></P>
            <UL>
              <LI><FONT color=#800000 face=Arial size=1>The internal chip could 
              be ruined by static from your nylon shirt, nylon carpets or 
              air-conditioned office. This problem also affected the production 
              facility, leading to a large number of failures before the watches 
              even left the factory. The result was that the display would 
              freeze on one very bright digit, causing the batteries to overload 
              (and occasionally explode).</FONT> </LI></UL>
            <UL>
              <LI><FONT color=#800000 face=Arial size=1>The accuracy of the 
              quartz timing crystal was highly temperature-sensitive: the watch 
              ran at different speeds in winter and summer.</FONT> </LI></UL>
            <UL>
              <LI><FONT color=#800000 face=Arial size=1>The batteries had a life 
              of just ten days; this meant that customers often received a Black 
              Watch with dead batteries inside. The design of the circuitry and 
              case made them very difficult to replace.</FONT> </LI></UL>
            <UL>
              <LI><FONT color=#800000 face=Arial size=1>The control panels 
              frequently malfunctioned, making it impossible to turn the display 
              on or off - which again led to exploding batteries.</FONT> 
</LI></UL>
            <UL>
              <LI><FONT color=#800000 face=Arial size=1>The watch came in a kit 
              which was almost impossible for hobbyists to construct. 
              <I>Practical Wireless</I> magazine advised readers to use two 
              wooden clothes pegs, two drawing pins and a piece of insulated 
              wire to work the batteries into position. You then had to spend 
              another four days adjusting the trimmer to ensure that the watch 
              was running at the right speed.</FONT> </LI></UL>
            <UL>
              <LI><FONT color=#800000><FONT face=Arial size=1>The casing was 
              impossible to keep in one piece. It was made from a plastic which 
              turned out to be unglueable, so the parts were designed to clip 
              together--which they didn't.&nbsp;</FONT><BR></FONT>
              <LI><FONT color=#800000 face=Arial size=1>A very high percentage 
              of Black Watches were returned, leading to the legend that 
              Sinclair actually had more returned than had been manufactured. 
              The backlog eventually reached such monstrous proportions that it 
              still hadn't been cleared <I>two years</I> later.</FONT> </LI></UL>
            <P>&nbsp;</P></TD></TR>
        <TR>
          <TD height=2015 width="70%">
            <H2 align=center style="TEXT-ALIGN: center">&nbsp;</H2>
            <H2 align=center style="TEXT-ALIGN: center"><SPAN 
            style="mso-bidi-font-size: 18.0pt"><FONT color=#800000 size=4><A 
            name="Atomic Clocks">Atomic Clocks<O:P> 
            </A>&nbsp;<BR></FONT></SPAN><IMG border=0 height=92 
            src="Cesium-atomic-clock_files/molecul.gif" width=106></H2>
            <P><SPAN style="COLOR: black"><FONT size=3>Termed NIST F-1, the new 
            cesium atomic clock at NIST, the National Institute of Science and 
            Technology, in Boulder, Colorado is the nation's primary frequency 
            standard that is used to define Coordinated Universal Time (known as 
            UTC), the official world time. Because NIST F-1 shares the 
            distinction of being the most accurate clock in the world (with a 
            similar device in Paris), it is making UTC more accurate than ever 
            before. NIST F-1 recently passed the evaluation tests that 
            demonstrated it is approximately three times more accurate than the 
            atomic clock it replaces, NIST-7, also located at the Boulder 
            facility. NIST-7 had been the primary atomic time standard for the 
            United States since 1993 and was among the best time standards in 
            the world.<O:P> </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>NIST F-1 is referred to 
            as a fountain clock because it uses a fountain-like movement of 
            atoms to obtain its improved reckoning of time. First, a gas of 
            cesium atoms is introduced into the clock's vacuum chamber. Six 
            infrared laser beams then are directed at right angles to each other 
            at the center of the chamber. The lasers gently push the cesium 
            atoms together into a ball. In the process of creating this ball, 
            the lasers slow down the movement of the atoms and cool them to near 
            absolute zero.<O:P> </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>Two vertical lasers are 
            used to gently toss the ball upward (the "fountain" action), and 
            then all of the lasers are turned off. This little push is just 
            enough to loft the ball about a meter high through a 
            microwave-filled cavity. Under the influence of gravity, the ball 
            then falls back down through the cavity.<O:P> &nbsp; 
            </FONT></SPAN></P>
            <P align=center><SPAN style="COLOR: black"><FONT size=3></O:P><IMG 
            border=0 height=267 src="Cesium-atomic-clock_files/cesiummodel.jpe" 
            width=181><BR></FONT><FONT face=Arial size=1>The fountain action of 
            the cesium clock.</FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>As the atoms interact 
            with the microwave signal?depending on the frequency of that 
            signal?their atomic states may or may not be altered. The entire 
            round trip for the ball of atoms takes about a second. At the finish 
            point, another laser is directed at the cesium atoms. Only those 
            whose atomic states are altered by the microwave cavity are induced 
            to emit light (known as fluorescence). The photons (tiny packets of 
            light) emitted in fluorescence are measured by a detector.<O:P> 
            </O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>This procedure is 
            repeated many times while the microwave energy in the cavity is 
            tuned to different frequencies. Eventually, a microwave frequency is 
            achieved that alters the states of most of the cesium atoms and 
            maximizes their fluorescence. This frequency is the natural 
            resonance frequency for the cesium atom?the characteristic that 
            defines the second and, in turn, makes ultra precise timekeeping 
            possible. <O:P></O:P></FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>The 'Natural frequency' 
            recognized currently as the measurement of time used by all 
            scientists, defines the period of one second as exactly 
            9,192,631,770 oscillations or 9,192,631,770 cycles of the Cesium 
            Atom's Resonant Frequency. The cesium-clock at NIST is so accurate 
            that it will</FONT></SPAN><FONT size=3> neither gain nor lose a 
            second in 20 million years! </FONT><SPAN style="COLOR: black"><FONT 
            size=3></O:P></FONT></SPAN></P>
            <P align=center><IMG border=0 height=209 
            src="Cesium-atomic-clock_files/nist2.jpe" width=268><SPAN 
            style="COLOR: black"><FONT face=Arial size=1><BR>The cesium atomic 
            clock at the NIST.</FONT><FONT size=3></O:P> </FONT></SPAN></P>
            <P><SPAN style="COLOR: black"><FONT size=3>This new standard is more 
            accurate by a wide margin than any other clock in the United States 
            and assures the nation's industry, science and business sectors 
            continued access to the extremely accurate timekeeping necessary for 
            modern technology-based operations. <O:P></O:P></FONT></SPAN></P>
            <P align=center><SPAN style="COLOR: black"><FONT size=3>&nbsp;<O:P> 
            </FONT></SPAN><IMG border=0 height=290 
            src="Cesium-atomic-clock_files/cesium.jpe" width=396></P>
            <P>&nbsp;</P></TD>
          <TD height=2015 width="30%">
            <P align=center> 
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center>&nbsp;</P>
            <P align=center><FONT color=#800000><FONT size=1><A 
            name=A0019909><B>ce?si?um</B></A> </FONT><FONT size=1>(s<IMG 
            align=absBottom height=15 src="Cesium-atomic-clock_files/emacr.gif" 
            width=7><IMG align=absBottom height=22 
            src="Cesium-atomic-clock_files/prime.gif" width=4>z<IMG 
            align=absBottom height=15 src="Cesium-atomic-clock_files/emacr.gif" 
            width=7>-<IMG align=absBottom height=15 
            src="Cesium-atomic-clock_files/schwa.gif" width=6>m)</FONT>.<FONT 
            size=1> <I>n.&nbsp;<BR>Symbol </I><B>Cs<BR></B>A soft, silvery-white 
            ductile metal, liquid at room temperature, the most electropositive 
            and alkaline of the elements, used in photoelectric cells and to 
            catalyze hydrogenation of some organic compounds. Atomic number 55; 
            atomic weight 132.905; melting point 28.5°C; boiling point 690°C; 
            specific gravity 1.87; valence 1.<BR><BR>Discovered by spectroscopy 
            in 1860 by Robert<U> Bunsen </U>and Gustav Kirchhoff.&nbsp;<BR>One 
            gram of cesium is an ample supply for a typical atomic clock to run 
            for one year.<BR><BR>A gram of cesium could be found in about a 
            cubic foot of ordinary granite. Natural cesium is pure cesium-133 
            (55 protons and 78 neutrons in the nucleus, 55+78=133): it is 
            non-radioactive.</FONT></FONT></P>
            <P>&nbsp;&nbsp;&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P>
            <P>&nbsp;</P></TD></TR>
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          <TD height=19 width="70%">
            <P align=center><B><A 
            name="Links to Clock, Watch, Time and Horology Websites"><FONT 
            color=#800000 size=4>Links to Clock, Watch, Time and Horology 
            Websites</FONT></A></B></P></TD>
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          <TD height=255 width="70%">
            <P align=center class=MsoNormal><SPAN 
            style="FONT-FAMILY: Arial"><FONT size=3><BR><B>?Ultrasonic 
            Ferroelectrics Frequency Control?</B><BR><A 
            href="http://www.ieee-uffc.org/fc"><SPAN 
            style="mso-bidi-font-size: 10.0pt">www.ieee-uffc.org/fc</SPAN></A><O:P> 
            </O:P></FONT></SPAN></P>
            <P align=center class=MsoNormal><SPAN 
            style="FONT-FAMILY: Arial"><FONT size=3><B>?Walsh Brothers Craftsmen 
            Watchmakers &amp; Jewelers?</B><BR><A 
            href="http://www.walshbrothers.co.uk/">http://www.walshbrothers.co.uk/</A><O:P> 
            </O:P></FONT></SPAN></P>
            <P align=center class=MsoNormal><SPAN 
            style="FONT-FAMILY: Arial"><FONT size=3><B>?Clockmakers 
            Newsletter?<O:P> </B></O:P><BR><A 
            href="http://www.clockmakersnewsletter.com/">http://www.clockmakersnewsletter.com/</A><O:P> 
            </O:P><O:P></O:P><O:P></O:P></FONT></SPAN></P>
            <P align=center class=MsoNormal><SPAN 
            style="FONT-FAMILY: Arial"><FONT size=3><B>?Clockstop.com?<O:P> 
            </B></O:P><BR><A 
            href="http://www.clockstop.com/">http://www.clockstop.com/</A><O:P> 
            </O:P><O:P></O:P></FONT></SPAN></P>
            <P align=center class=MsoNormal><SPAN 
            style="FONT-FAMILY: Arial"><FONT size=3><B>?Horology ? The Hands of 
            Time</O:P>?<O:P> </B>&nbsp; <BR><A 
            href="http://horology.magnet.fsu.edu/">HTTP://horology.magnet.fsu.edu<BR><BR></A><B>"All 
            Clock-Wise"</B><A 
            href="http://www.allclockwise.com/"><BR>www.allclockwise.com</A></FONT></SPAN></P>
            <P align=center>&nbsp;</P></TD>
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