Engines of Our Ingenuity

No. 722:
JULIUS ROBERT MAYER

by John H. Lienhard

Click here for audio of Episode 722.

Today, a story about blood and heat. 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.

In 1840, Robert Mayer was 26. That year he shipped to the East Indies as the surgeon on a Dutch vessel. Afterward, he came back to Germany, married, and settled down as a town doctor. It might seem he was done with adventure.

But something touched him in Java, and it changed his life. Whether or not it changed history is moot. But insight came on Mayer in 1840, and science historians still talk about it.

He was letting blood from sick sailors. You do that by lancing a vein. Venous blood carries less oxygen than arterial blood. It runs darker. The first time Mayer opened a vein in Djarkata, blood ran far too red. He thought he'd hit an artery.

Then he found that's normal in the tropics. And he realized: People burn less of the food they eat. They generate less heat.

We knew that food fuels our power output. Now Mayer realized that it also fuels our heat supply. And we need a lot less heat in Djakarta than we do in Europe.

In 1840 we didn't know that heat and work can be traded back and forth. Mayer thought about that red blood on the long trip back. And he tumbled to the truth of energy conservation.

Mayer identified our most important physical law. But he didn't know classical physics. He didn't know formal math. He wrote a clumsy paper about the idea, and the editor ignored it.

So Mayer went back to study physics. Then he wrote a better paper in 1842. Meanwhile, a young Englishman, James Joule, was measuring how many foot-pounds of work made a Btu. By 1847, Joule had honed his accuracy to 99 percent.

And there the plot thickens. Mayer had spun a correct theory for the number of foot-pounds per Btu. But no one would believe it until measurements were more complete.

Physicists sorted through Mayer's theory and Joule's experiment. When they finally resolved the whole business, they overlooked Mayer. By 1850 Mayer was angry and frustrated. He attempted suicide. For years after, he was in and out of asylums.

Finally, in 1863, the Englishman John Tyndall wrote an important text: Heat: A Mode of Motion. It began and ended with Mayer. Mayer was vindicated.

Twenty years before, insight had touched him in Java. His vision of bright blood and heat really did change history. But first, professional scientists -- men untouched by visions -- had to put it in familiar terms. In the meantime, Mayer's insight had almost driven him mad. And I hear words by the poet Rilke:

. . . if you set this brain of mine on fire,
then on my blood I yet will carry you.
I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.
(Theme music)


Lindsay, R.B., Julius Robert Mayer: Prophet of Energy. New York: Pergamon Press, 1973.

Turner, R.S., Mayer, Julius Robert. Dictionary of Scientific Biography. Vol. ??, (C.C. Gilespie, ed.) Chas. Scribner's Sons, 1970-1980. pp. 235-240.

Deickmann, F., Vor 150 Jahren: Robert Mayer und die Erhaltung der Energie. Lufthansa Bordbuch, March, 1991, pp. 52 and 54.

Rukeyser, M., Willard Gibbs. Garden City, NY: Doubleday, Doran, and Co., 1942. (Poet Muriel Rukeyser begins her biography of the thermodynamicist J.W. Gibbs with an account of Mayer's recognition of the conservation of energy in the year after Gibbs was born.)

The Correlation and Conservation of Forces: A Series of Expositions. (E.L. Youmans ed.). New York: D. Appleton and Co., 1865.

Tyndall, J., Heat Considered as a Mode of Motion. New York: D. Appleton and Co., 1863.

Rilke, R.M., Poems from the Book of Hours (tr. B. Deutsch). New York: New Directions Pub. Corp., 1941.

Today, Mayer is once again largely forgotten in textbooks. We give most of the credit to Joule. However, the building block of Mayer's theory was that the conversion factor, J ft-lb/Btu, (or dyne-cm/cal or N-m/J) could be obtained from,

J = R/(Cp - Cv)
R is the ideal gas constant expressed in work units. Cp and Cv are the specific heats at constant pressure and constant volume. They're expressed in heat units.

Our textbooks simply write, R = Cp - Cv, and we presume that students know how to convert heat and work units. One problem with Mayer's work was that he had an accurate value of R, but Cp and Cv data were flawed. Therefore his value of J was far less accurate than Joule's.

We call the law of conservation of energy the First Law of Thermodynamics. It says energy is conserved over its many forms -- potential, kinetic, thermal, and so on. Energy can neither be created nor destroyed. In 1850 another German, Clausius, codified the law in the words, "Die energie der Welt ist Konstant," where we take the word Welt to mean universe, not world.

Today, of course, we amend the First Law to acknowledge that matter and energy are also interchangeable in nuclear reactions.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

Previous Episode | Search Episodes | Index | Home | Next Episode