Don’t Take Ye Olde English Wooden Nickels

Photo by the Author

By The Metric Maven

Bulldog Edition

I’ve always liked wood. My Grandfather was a carpenter, my father also knows how to work with wood. I, alas, do not. My father can generally recognize different woods, I haven’t a clue. The variety of woods that exist is astonishing. I recall reading about how the English carpenter and clockmaker John Harrison (1693-1776), used a wood called Lignum vitae, to construct wooden clocks. This wood actually has the property that is is self-lubricating, which allowed Harrison to make bearings and gears of it for his pendulum clocks. It is also one of the hardest woods in nature. In my youth I marveled at the Balsa wood rubber band driven airplanes available at the local dime store. I also have an interest in photographing wooden grave markers. An image of one of these “tombstones” I photographed is shown in the photo above.

I thought back on all this when paging through an old book called Science in Everyday Things by Engineer William C. Vergara and published in 1958. The book is a list of questions with answers, and one of them is: “Does all wood float?” What I assume he means is that given a solid cube of wood, will it float in water? When Vergara offers his answer, he informs his readers that the density of water is 62.5 pounds per cubic foot. Any wood with a density above this will sink and any below this will float. What struck me was the contrived and arbitrary nature of this value. It reminds me of the freezing point of water being defined as 32 degrees, an arbitrary magic number to be remembered on the Fahrenheit scale, because of poor measurement planning.

What struck me even more was that I was still going along with all the people who use kilograms per meter cubed. In my view, this is a vestigial Ye Olde English use of metric, which should be diminished. Density is the mass of an object divided by its volume. The everyday common volume unit allowed in metric is the liter, and a liter of water is essentially a kilogram. This means that a liter of water has a density which may be written as 1000 grams/liter. Both grams and liters are familiar units in the everyday world of an average person in a metric country. If a wood’s density is below 1000 grams/liter it will float, if it is above 1000 grams/liter it will sink. This is a nice Naughtin’s Laws friendly way to express water’s density, and it does not involve recalling a number like 62.5 pounds per cubic foot. This method essentially relates the specific gravities of the woods in an elegant fashion. It allows one to rationally list the densities of various woods in a way which one can immediately realize if they would float or not:

Wood             Density (g/L)

Balsa                           96
Yellow Pine                650
Maple                         704
Hickory                       816
Water Gum Tree      1000         (Density of water)
Black Ironwood        1040
Poison Ash              1104
Arapoca                   1200
Lignum Vitea           1229
Qeubracho              1393

Balsa is the lightest of the woods and a cube of it will clearly float in water. Yellow Pine, Maple and Hickory will also all float in water. Yellow pine was chosen for use in the caissons that were used to construct the Brooklyn Bridge.[1] Southern Yellow Pine was chosen for it’s ability to withstand large pressure and for the considerable amount of resin it contains. This makes it very resistant to rotting. Wood from the aptly named Water Gum Tree has neutral buoyancy, that is, it has essentially the same density as water and is compelled to neither float nor sink in it. A block of Water Gum Tree wood is like a helium balloon which floats at a stable position, neither rising nor falling to the floor. The word Quebracho means “Ax Breaker.” Given its high density, this name seems appropriate.

In his last sentence Vergara states: “Since wood weighing more than 62.5 pounds per cubic foot will sink, it can be seen that many  kinds of woods cannot possibly float.”

This is true for a single monolithic block of wood, but all these woods can be used to make vessels which will float, they only need to displace enough water to do so. The Civil Engineering students at Iowa State University each year create a concrete canoe. The density of concrete? It’s 2400 grams per liter. But concrete is not nearly as dense as steel which is about 8000 grams per liter. The hollow interior of a canoe or ship decreases the overall density of the ship enough to bring it well below the 1000 grams/liter threshold, which in turn allows it to float. Allowing for shaping, all wood will float.

I very much encourage the use of grams/liter for expressing density. I completely discourage the use of the cgs leftover, grams/cubic centimeter. In the case of steel its density is 8.05 g/cc. I also mostly tend to discourage the use of kilograms per cubic meter, as the units are out of the range of everyday measurement experience. It is, however,  very easy to convert from kg/m3 to g/L. For instance, the density of steel is 8000 kg/m3 which is 8000 g/L. The conversion factor is one. The numerical values are the same, just change the units. It’s just that easy, as the metric system is, and should be, when it’s employed in an articulate manner. People who insist on using Ye Olde English units like pounds per cubic foot—are just dense.

[1] The Great Bridge, David McCullough, Simon and Schuster, New York pg. 174-175.

The Story of Measurement

The Story of Measurement by Andrew Robinson

By The Metric Maven

The book The Story of Measurement by Andrew Robinson is a magnificent work of graphic arts. Page after page of eye catching color graphics assault the senses. The illustrations are just candy for the eyes. It is a truly magnificent “coffee table book.”  In the introduction the author impresses upon the reader how prevalent measurement is in our everyday lives:

A few minutes’ reflection reminds us that measurement pervades our everyday lives. In no particular order, we constantly encounter: clocks, calendars, rulers, cloth sizes, floor areas, cooking recipes, sell-by-dates, alcohol content, match scores, musical notation, map scales, internet protocols, word counts, memory chips, bank accounts, financial indexes, radio frequencies, calculators, speedometers, spring balances, electricity meters, cameras, thermometers, rainfall gauges, barometers, medical examinations, drug prescriptions, body mass indexes, educational tests, opinion polls, focus groups, questionnaires, consumer surveys, tax returns, censuses and many other forms of measurement — all of which serve to reduce the world to numbers and statistics.” (Page 7)

One can imagine my anticipation when I read that paragraph. One could only believe a good read was to follow. What would he have to say about the metric system?  We don’t have to wait long, on page 13 he states: “But the acute economic difficulties experienced with the new [metric] system persuaded Napoleon to rescind the original legislation in 1812.” Author Andrew Robinson indicates that only scientists were upset at this reversal. This statement seemed at odds with what I understood to have occurred historically in France. I made a mental note to look into it.

Robinson then indicates that Thomas Young (1773-1829) did not support “the legislative enactment of uniform weights and measures in Britain.” Young had written an article for the Encyclopaedia Britannica in 1823 and the author quotes from it. Young sees France’s experiment with creating a single measure as a failure and argued that:

…the British government should ‘endeavor to facilitate both the attainment of correct and uniform standards of legal existing measures of all kinds, and the ready understanding of all the provincial and local terms applied to measures, either regular or irregular, by the multiplication of glossaries and tables for the correct definition and of such terms.’

The more measurement units, the merrier!? Then it hit me. Thomas Young. I’d tried to read the book The Last Man Who Knew Everything two times and found it completely unable to engage my enthusiasm. It is about the life of Thomas Young. I went to my bookshelf and located it. The book was written by, you guessed it, Andrew Robinson. This was not a good portent, but I tried to be optimistic. Then I read this:

In the telling words of the economic historian Witold Kula in Measures and Men: `The reform that standardized weights and measures, which had been so ardently desired for centuries and so widely demanded by the common people on the eve of the Revolution, extolled by so many of the truest revolutionaries and conceived by the finest scientific minds of the day, had, ultimately, to be imposed upon the people.’

Economic historian? Does it disturb the economic historian that currencies are imposed on the public? Should we therefore we should go back to barter? Robinson introduces an economic historian as an indirect backdoor way of introducing an old canard, market Darwinism, as an argument against the metric system without actually straightforwardly stating it. Later, on page 81, Robinson goes further:

Even scientists sometimes take refuge in non-standard units, more ‘human’ than, say, gigametres (109 m) and nanometres (10-9 m). Astronomers like the ‘astronomical unit’ (AU), equaling the mean distance between Sun and Earth; from the Sun to Jupiter is 5.20 AU, a figure easier  to remember than the metric distance, 778 gigametres. Chemists are fond of the angstrom (Å), 0.1 nanometer, for measuring molecular distances; the radius of the chlorine molecule is about 1 (Å).

Oh the humanity!—of unfettered unit proliferation!? I recommend that Robinson read my essay Long Distance Voyager. There he will see evidence of the great utility the metric system has for describing astronomical distances. The angstrom is an exclusionary unit, which acts as a barrier to an integrated understanding of sizes at the nanometer level.

Along the way Robinson offers up this about the metric system:

Among the US public, Gallup polls showed that between 1971 and 1991, awareness of the metric system increased from 38 to 80 percent, but the proportion of those favoring its adoption fell from 50 to 26 percent. (page 31)

One should note that he uses the word awareness, which does not imply they understand the metric system. I’m more aware of Cricket after working with English and Indian engineers, but I can clearly claim I do not understand it and probably would be less inclined to favor playing it.

Robinson also has an incredible fetish for fractions and milliSaganistic prose (i.e. millions and millionths). On page 84 he discusses the 19th century mystery of how and why pollen grains vibrated in water, which is called Brownian motion:

From theory, Einstein calculated that particles in water at 17 degrees C with a diameter of a thousandth of a millimetre — that is, 10,000 times bigger than atoms — should move a mean horizontal distance of 6 thousandths of a millimetre in one minute.

I’ll take a stab at editing this set of prose using metric prefixes:

From theory, Einstein calculated that one micrometer sized particles of pollen, in water at 17 degrees C, would move a mean horizontal distance of six micrometers in one minute, in response to being jostled by picometer sized atoms of water, which are 10 000 times smaller than the pollen particles.

Robinson made me pine for the excellent monograph Science & Music by Sir James Jeans when I read:

….and the amplitude [of a sound wave] dictates the sound pressure. At the threshold of hearing, the displacement is a mere millionth of a millionth of a metre (about one fifth of the radius of a hydrogen atom!).

Perhaps?:

“….and the [perceived] amplitude dictates the sound pressure. At the threshold of hearing, the displacement is a mere picometre (about one fifth of the radius of a hydrogen atom!).”

Robinson continues:

and the pressure difference between the peak and the trough of the wave is a two hundredth of a thousandth of a pascal (compare normal atmospheric pressure, which is about 100,000 Pa).

Possibly?:

and the pressure difference between the peak and the trough of the wave is 5 micropascals (compare normal atmospheric pressure, which is about 100  kilopascals or 20 000 000 000 times larger).

One would hope that’s enough zeros for histrionics’ sake!

An example of Robinson’s fetish for fractions is shown in his caption of a photograph which shows Physicist Richard Feynman (1918-1988) viewing a tiny electric motor. The motor was engineered in response to a famous technical challenge he made:

Perhaps 750 microwatts of power from a motor which is 4.25 micrometers in diameter? After all how many people own a horse these days?

In Robinson’s section on screws he only mentions Joseph Whitworth, and passes over metric screws completely. When discussing calorie counting he mentions kilojoules only once, essentially as a token conversion factor.

It is a strange book on the story of measurement which has so little of the metric system or its usage in it, but that is what The Story of Measurement is. Now and then, despite his sprinkling of unnecessary centimeters—ok—I’m of the opinion that all centimeters are unnecessary, he uses mm in a way with large decimals that comports with my understanding of accepted metric usage:

The zeros are separated with spaces by three. He uses millimeters. It gives an idea the value is getting smaller—a lot smaller. This is a nice table in a book which is dominated by large fractions and mixed usage. This table is fine, and might be the best presentation, but an alternative way he could have constructed the table might have been using picometers with the whole number rule:

1791  Quarter meridian of of Earth  +/-  60 000 000 pm
1889  Prototype bar                          +/-    2 000 000 pm
1960  Krypton Wavelength                +/-           7000 pm
1983  Speed of Light                         +/-             700 pm
Today Improved Laser                       +/-               20 pm

Unfortunately good examples of metric usage, like his table, are few and far between in this book. There even seems to be a ubiquitous underlying hostility to metric usage just barely below the surface of this narrative. Is there much else I can say that I like about The Story of Measurement? Uh…did I mention the graphics are visually attractive?