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From: cosell@bbn.com (Bernie Cosell)
Newsgroups: comp.lang.postscript
Subject: Re: Oh, what's the point? (was points and rulers)
Message-ID: <51118@bbn.COM>
Date: 18 Jan 90 21:50:10 GMT
References: <50949@bbn.COM> <563@purdey.advsys.UUCP>
Sender: news@bbn.COM
Lines: 34

brian@advsys.UUCP (Brian Rippon) writes:

}In article <50949@bbn.COM> news@bbn.COM (News system owner ID) writes:
}>The "conventional American" point IS kind-of metricized: The 1886
}>standard from the United States Type Founders' Association was based on
}>the observation that the American-pica had an almost-relationship to
}>the cm:
}>
}>     83 picas ~= 35 cm
}>
}>and so they standardized on exactly "83 picas = 35 cm". 

}Well, I'm confused. How big was a centimetre in the US in those days?
}Since SI, there are 2.54 cm/inch, so you would get 72.2811428571... points/inch.

I did some poking, and I think that you are correct: the "length of the
inch" probably changed.  The French instituted the metric system in
1799.  The point was "standardized" in 1886, and in fact probably *did*
work out to be 72.28 points/inch.  In 1893 the United States
officially reconciled its units with the Metric units.  I could
easily believe that the length of the foot [or the length of the
meter... depends on your point of view...:-)] changed by one part in
ten-thousand at that point.  In particular, notice that the "exact"
value for the centimeter is by definition 2.54 cm/inch.  That looks
suspiciously like "three significant digits", and so would be an
approximation which would introduce an error at the fourth digit...
and look at what position we seem to have picked up some error at....

}That given, it's all an approximation, and 72 sounds as good a number
}as any other. Fournier and Adobe chose well.

I agree.  Time to let this thread die....

 /Bernie\