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MarekOtisk
Plate6.TheRouenabacus[R](11
MS489,f.68v169r
th
century);drawingacc.toRouen,Bibliothèquemunicipale,
Secondly,thereisamanuscriptdatingbacktothe12
th
century(Paris,Bib-
liothèquenationaledeFrance,MSLat.7231),whichsummarizestextsdedi-
catedtotheliberalarts,mainlyonrhetoric,andonitslastfolio(85v),thereis
adrawingofanabacus[Pa](seeplate7),whichdatesbacktothe11
th
century
(mostprobablyfirsthalfofthecentury)
45
.Thereasonforsuchanearlydating
isitsstrikingsimilaritytothedrawingofanabacus[B]fromthelate10
th
cen-
tury.Bothdrawingsdepicta30-columnabacuswithallthreesizesofarches
roofingthecolumnswiththelettersC,D,andM/S([B]doesnotincludethe
Ssiglum),andbotharehorizontallydividedintofoursections.Inthefirst,
topmosthorizontalsection,inbothcases,thereareidenticallywrittenmarks
fordecimalscalesfrom10
0
to10
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(abacus[Pa],unlike[B],doesnotinclude
symbolsforfractionsinthefirstthreecolumnsontheright)andbythebound-
arylinebetweenthefirstandsecondhorizontalsections,thescalesinvalues
ofthousandsarewritteninanidenticalway(inthecaseof[Pa],theyarewrit-
tenabovetheborderline,i.e.inthebottompartofthefirstsection,whilein
thecaseof[B],theyarewrittenunderthedividingline,i.e.intheupperpart
ofthesecondsection).Thefourthsectioninbothcasesrepresentsfractions,
theirnames(theauthorofthe[Pa]abacusdistortedthenameofsestertius),
symbols(verysimilarly,thereareonlytinydifferencesinbothdrawings),and
mutualratiosbetweenfractions.However,thereareseveralsignificantdiffer-
encesbetweenbothdrawings.While[B]statesthetriplenumeralvaluesof
45
SeeforexampleCh.Burnett:TheAbacusatEchternach…,p.92.
