Metrication matters - Number 14 - 2004-07-10
1 Feedback - notes and comments from readers
3 Oddities - measurements from around the world
4 Tips - pointers and methods to make your measurements easier.
5 Signs of the times
7 Q&A - readers' questions and answers
8 Rule of thumb
10 Hidden metric
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Doesn't the internet make the world seem small! I received some support for
the story about the tatami and the jo in the last issue. This came to me
from Japan via Mike Joy, an Australian who is now in New Zealand. Mike's
Japanese friend, Toshiko, wrote:
'But Kiyou Tatami size is smaller. Many modern apartments or mansions use
small size now.
'A long time ago and old houses (the tatami) was bigger'.
I had an exhilarating evening earlier this week at a Church Fellowship
evening. Although I am not religious, I accepted the invitation (and the
challenge) to speak to this group about the metric system. It turned out to
be great fun, and I really enjoyed the opportunity to research early
references to all the measurement words that I could find in the Bible. For
more details see 'History' below.
In a report about an anti-war protest in London a local newspaper reported:
In London, two anti-war protesters climbed the landmark Big Ben clock tower
at the Houses of Parliament, unfurling a banner reading 'Time for Truth'
after they reached the clock face 328 feet (100 metres) above the city.
I wonder whether the clock faces of the Westminster Clock* really are
exactly 100 metres above the ground. That would be in keeping with the size
of Trafalgar Square, which was designed to be exactly 100 metres along each
side. Trafalgar square was named for Lord Nelson's success at the Battle of
Trafalgar in 1805. Admiral Lord Nelson is immortalised with a statue atop
Nelson's Column, designed so that the Nelson's statue is 50 metres above the
* Big Ben is the bell that strikes the hours. The clock is the Westminster
Clock. Even tourist books in London get that wrong.
Most paper comes classified as 80 grams per square metre. You can get
heavier or lighter grades but this seems to be the most common. As the
A-series of paper sizes were devised mathematically (in Germany in the
1930s) this piece of information can be useful because each piece of the
most common office paper, A4, has a mass of 5 grams. I once used a piece of
A4 paper, on a small set of scales, to measure 5 grams of herbs for a
recipe. But this can be more regularly useful for checking the mass of your
mail. When you are putting A4 sheets into an envelope to send by post, you
simply count the sheets, multiply by five grams per sheet, and then add
another 10 grams for the envelop.
By the way, I know that there is an issue of hygroscopicity that has to do
with the current temperature and humidity, but for many practical
applications the idea that a piece of A4 paper has a mass of 5 grams is a
very useful approximation.
5 Signs of the times
This morning, I heard a radio report of a new Walkman product that is to
challenge the Apple iPod. The reporter informed me that it contained a hard
disk that was 'nearly two inches' in diameter. Now I wonder what the real
size could be; could it be 50 millimetres by any chance.
In 'Absolute Zero Gravity', Devine and Cohen tell this story. Three
statisticians went deer-hunting with bows and arrows. They crept through the
forest until they spotted a magnificent buck. The first statistician shot,
and his arrow landed five metres to the right of the deer. The second one
shot, and her arrow landed five metres to the left of it. So the third
statistician jumped out of the bushes and shouted 'We got him! We got him!'
It seems that hiding metric measures is quite common in woodworking
activities in the USA. This question and answer are from the woodweb site.
'What are some pros and cons of going metric? We purchased three new
machines recently, including a 'Weeke' point to point, and the question of
converting to metric keeps coming up.
'I heartily endorse the idea of full metric production in the shop. Most
staff start out not liking it but come around quickly when they get rid of
the fractions. Our only ongoing difficulty has been that the design end of
our business must remain in imperial dimensions for customer reasons and the
conversion issues are most easily handled by the computer packages we have.
Cabnetware does a good job of letting you design in imperial and then build
8 Rule of thumb
Adult humans vary from about 50 kilograms to 100 kilograms. If you are much
below 50 kilograms you are probably not very well. A very large football
player might be as much as 140 kilograms. However, to estimate the average
mass of people in a lift or elevator use 70 kg for an adult and 40 kg for a
By the way, I am always on the lookout for 'Rules of thumb' to add to my collection. I prefer metric ones but I also like to convert 'Rules of thumb' from old units to SI units. Please send your 'Rules of thumb' to
I was talking to a Biblical scholar recently when the subject of measurement
came up (funny that!). I asked her what she understood by a ephah. She
replied a few days later with definitions of these measures: bath, ephah,
hin, homer, koros, qaneh, saton, shekel, and cubits great and small. But,
more interestingly to me, our research turned up these quotations from the
King James Bible:
The ephah and the bath shall be of one measure, that the bath may contain
the tenth part of an homer, and the ephah the tenth part of an homer: the
measure thereof shall be after the homer.
Concerning the ordinance of oil, the bath of oil, ye shall offer the tenth
part of a bath out of the cor, which is an homer of ten baths; for ten baths
are an homer.
It would appear that decimal measuring methods might be much older than I
previously thought, as Bible scholars tend to date the book of Ezekiel at
about 5000 BC.
10 Hidden metric
Makers of manufactured fibres for clothing (such as acrylic, nylon,
polyester, and rayon) use the word, 'denier' to describe the fineness of
their fibres. The lower the number, the finer the fibre – the higher the
number, the heavier the fibre. This gives the illusion of an ancient,
arcane, and therefore respectable, old measure. In fact, a denier is simply
the number of grams in 9000 metres of artificial fibre. A denier simply does
not exist without the support of the metric system. And before you ask, I
have no idea why 9000 metres was chosen.
Pat Naughtin is a writer, speaker, editor, and publisher. Pat has written several books and he has edited and published many others. For example, Pat was the lead writer of a chapter of a chemical engineering encyclopedia, and recently he edited the measurement section for the Australian Government 'Style manual: for writers, editors and printers'. Pat has been recognised by the United States Metric Association as a Lifetime Certified Advanced Metrication Specialist.
Copyright notice: © 2004 Pat Naughtin All rights reserved. You are free to quote material from 'Metrication matters' in whole or in part, provided you include this attribution to 'Metrication matters'. 'This was written by Pat Naughtin of "Metrication matters". Please contact for additional metrication articles and resources on commercial and industrial metrication'. Please notify me where the material will appear. Copying for any other purpose, whether in print, other media, or on websites, requires prior permission. Contact:
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