Today, oil by the barrel. The
University of Houston's College of Engineering presents this series about the
machines that make our civilization run, and the people whose ingenuity created them.
This summer of 2006, all America watches the spiraling
cost of a barrel of oil. As we burn the stuff faster and faster, it grows more
precious, and the world warms to its frenzied consumption. But to see the oil
barrel as an artifact, rather than an emblem of our troubled
times, let's read Robert Hardwicke's 1958 book The Oilman's Barrel.
The wooden barrel was a 3rd-century Roman invention and he shows how the word barrel became
a unit of measure. But, alas, the history of units is a terrible morass. Measures
of weights and volumes, for example, are constantly confused with one another,
since so many things weigh very nearly the same as water. The gallon was defined
in medieval times so it would represent over sixty thousand grains of wheat. That
would be a unit of weight, not volume. By various accidents of history, the gallon
eventually came to be defined as a volume, however. The American and British gallons
are 231, and 277, cubic inches.
Containers for practical commerce had to be much larger than a gallon, so barrels had
long since been developed, and they eventually took six basic sizes: the firkin, the
kilderkin, the barrel, the hogshead, the butt, and the tun (spelled t-U-n).
The size of each varies somewhat. They were defined slightly differently for wine, beer, grain,
and so forth, and definitions changed from country to country. But a firkin is typically
nine gallons and the tun is 252 gallons. That means that a tun filled with water is very
close to 2000 pounds -- hence our term ton (spelled t-O-n.)
The beer barrel held 42 US gallons, and they were first used to ship oil in the 19th century.
That's still the size we refer to when we speak of a barrel of oil. Yet, if oil should happen
to be moved in a unit container today, it'll be a 55-gallon steel drum, with a capacity nearer
that of a hogshead than a barrel.
Wooden barrels were marvels of engineering design. Their staves cannot be allowed to bend,
so they're given an outward arch. The staves act like stone arches when you press on their
sides. Instead of bending, they stay rigid and transmit the force onto solid top and bottom
plates. They let one roll a weight that one could never lift. And, since the barrel meets
the floor only at one point, it's easy to steer it as it rolls.
In their time, barrels were used to hold everything -- meat, gunpowder, spirits -- even people
going over Niagara Falls and living to tell of it. As the death toll
among builders of the Panama Canal grew, the companies began using
barrels to ship the cadavers back to medical schools in the US.
Now their main use is to store wine, beer, and liquor. Bourbon is cured in charred oaken
barrels where a chemical process releases sugar from the oak, and adds a slight natural caramel
flavor. But the place barrels really survive is in the abstract digital accounting of our vast
consumption of oil -- even though crude oil never touches wood on its long road to our hungry
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
R. E. Hardwicke, The Oilman's Barrel. (Norman, OK: Univ. of Oklahoma Press, 1958).
Thirty-two grains of wheat makes a pence, twenty pence makes an ounce, 12 ounces, a pound
and eight pounds makes a gallon. That's 61,440 grains of wheat adds up to a gallon of wheat.
(And we know that a gallon of wheat will weigh a lot less than a gallon of water.)
Here's a useful online history of barrels,
And here's a page on British Imperial units which differ from ours,
See also, W. Curtis, The Brilliance of the Barrel. Invention & Technology, Vol 21,
No. 4, Spring, 2006, pp. 36-43. (My thanks to Pat Bozeman, UH Libraries, for suggesting an episode
from this source.)
A machine for shaping the metal hoops that hold a barrel together, 1892 Appleton Cyclopaedia of Applied Mechanics
The Engines of Our Ingenuity is
Copyright © 1988-2006 by John H.