Today, a piece of apparatus and a piece of history.
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.
An unexpected article by
Theodore Sterling in Rittenhouse's Journal of
Scientific Instruments: The title, "Marcet's
Apparatus," calls to mind the great
early-19th-century textbook writer,
Jane Marcet. But this item is credited to
François Marcet. Who is he?
First the article: It's about an instrument for
measuring the vapor-pressure of water. A small
spherical boiler is fitted with a thermometer and a
long mercury manometer. You half-fill it with
water, then heat it. The thermometer and manometer
give a sequence of pressures and the matching
boiling-point temperatures. The instrument is
limited by the height of the manometer. If it's
2½ feet high, you can measure up to twice
atmospheric pressure. If it's five feet high, you
can go to three atmospheres, and so on.
Marcet probably built this device around 1826 when
he was only 23. If that date is correct,
François Arago of the French Academy of
Sciences had done the same experiment three years
earlier. Arago mounted sections of pipe up the side
of a church tower and managed to measure
water-vapor pressures to 24 atmospheres. Author
Sterling tries to determine whether Arago or Marcet
originated the idea. He decides Arago was probably
But I thought there might be more to the story of
François Marcet, so I did some looking of my
own. Marcet was born in England, where he went by
the name of Francis. But he was living in
Switzerland when he did the experiments. It turns
out that Jane Marcet was his mother. She wrote her
first book, Conversations in Chemistry, when
he was a toddler. Jane Marcet's husband, Alexander,
was a noted Swiss physician. The family spent time
in both countries.
Jane Marcet was the focal point for women
scientists in England. She was well-connected, and
Arago was one of her European scientific friends.
That apparatus was almost certainly the fruit of
shared ideas, and its significance reached beyond
measuring water's boiling points.
Jane Marcet and François Arago both used
technology as a vehicle for social reform. She did
much to take women out from behind the "Crinoline
Curtain." He strove to bring the Industrial
Revolution to France, and that meant getting the
French to adopt the new English steam engines.
James Watt had been among the first to measure
vapor-pressures. Now both Arago and Jane Marcet's
young son were trying to improve that basic
In 1872, Francis Marcet (now 69 years old) edited a
14th edition of his mother's physics book. By then
steam engines were running at far higher pressures
than Marcet's, or even Arago's, apparatus could
reach, and those engines had transformed us. But
the apparatus was still a part of college courses.
Jane Marcet's books were still teaching students in
those courses. And France had, at last, become a
major steam-driven industrial nation.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
Sterling, T.C., Marcet's Apparatus. Rittenouse:
Journal of the American Scientific Instrument
Enterprise, Vol. 8, No. 4, 1994, pp. 110-113.
Marcet, J.H., Conversations on Natural
Philosophy. Boston: Lincoln, Edmonds & Co.,
1834. (This is one of many later editions of
Marcet's book. This particular edition bears the
name of J.L. Blake on its title page.)
I am grateful to Helen Coffeen for providing me
with issues of Rittenhouse and urging me to
do programs from their pages.
For more on Jane Marcet see Episodes 741, 744,
745, 828, and 950.
For more on François Arago, see Episodes
691, 704, and 1296.
This episode was written in 1998. In a 2010 email, Dr. John S. Reid,
of the University of Aberdeen Physics Dept., provided this
fascinating addition: "You mention a possible date of invention of 1826.
... Our University accounts record the purchase for teaching demonstration by the Professor of
Natural Philosophy at Marischal College, Aberdeen, of 'Marcet's steam
apparatus' from the London maker/supplier Al. Garden in the 1824/25
accounts. If it was being made in London then, it's invention in France
must have been a year or two earlier. We have a version in almost
pristine condition by Watkins and Hill, London instrument makers who were
in existence at that time, in our historic scientific instrument collection
derived from the University's teaching demonstration apparatus."
From Illustrations of Chemical
François Marcet's vapor-pressure measurement
The Engines of Our Ingenuity is
Copyright © 1988-1998 by John H.
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