Engines of Our Ingenuity

No. 1938:
DISCOVERING AIR

by John H. Lienhard

Today, we learn what air is made of. 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.

Strange thing the other day: In the M-volume of the Dictionary of Scientific Biography, I suddenly noticed that three successive M-names were all little-known seventeenth-century scientists. Two were Italian and one was French. All were born in the last years of the sixteenth century. And the work of each was connected to work done by Galileo and Torricelli on gases, liquids, and vacuums.

Too much coincidence for a random throw of the dice, yet that's what it was. My three M-names were Magiotti, Magni, and Magnenus. They were from Rome, Milan, and eastern France.

Magiotti worked with barometers. He helped us see that water expands or contracts when it's heated or cooled, but that pressure hardly affects it. He was first to verify experimentally that the speed of water leaving a nozzle varies as the square root of the height of the water above the nozzle.

The second of the three, Magni (like Galileo) was eventually accused of heresy. That was partly because he'd gotten crosswise with the Jesuits, but also because he (like Galileo) opposed the Church's Aristotelian science. Aristotle, he said, was wrong in saying that nature abhors a vacuum. To show that we could create a vacuum, he invented the barometer, independent of Torricelli and at about the same time as Torricelli.

The third of our three M's, Magnenus, specifically argued that matter was made of atoms, not Aristotelian Earth, Air, Fire, and Water. Magnenus began putting flesh and blood on atoms. He said, for example, that they had finite size, and were not mere points.

While Magiotti and Magni talked about barometers and vacuums, Magnenus told us what air was made of. He believed in only three kinds of atoms -- atoms of earth, of fire, and of water. But he also knew that air (or any gas) was a thin collection of atoms of one kind or another.

I've said before that invention is always the work of a Zeitgeist, not just one great thinker. Well here we watch a Zeitgeist, a spirit of the times, at work. So many people, many of whom actually knew Galileo, all worked this same problem from different an-gles. My three M's were at it along with the likes of Torricelli, Gassendi, von Guericke -- finish the list if you dare. Just be sure Galileo is on it with the rest.

A few Hellenic Greeks, and some Romans as well, had it right. But the idea did not yet converge around any of them, the way it later converged around Galileo. Without the Zeitgeist, scribes faithfully passed those ancient writings along, but what the writings said gained no acceptance. That's because invention is never the work of just one. Invention is always the work of many. Maybe that's what another Zeitgeist was telling me about invention, when those three M names popped off the page so unexpectedly.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


The three articles are all in the Dictionary of Scientific Biography (C.C. Gilespie, ed.) Vol. 9, New York: Charles Scribner's Sons, 1970-1980, pp. 13-17. The entries are: P, L, Rose, Magiotti, Raffaello; M. Fichman, Magnenus, Johann Chrysostom; and P. L. Rose, Magni, Valeriano.

A Homemade BarometerWould you like to make your own barometer? If so, click on the image to the right. You will get complete instructions as they were given on pages 188-189 of The Boy Mechanic, Book 1. Chicago: Popular Mechanics Co., 1915.

For more on these ideas, see, Episode 1553.





The Engines of Our Ingenuity is Copyright © 1988-2004 by John H. Lienhard.