DIRECTORY 335
CLAUDE BERNARD
1813–1878French physiologist Claude Bernard
was a pioneer in experimental
medicine. He was the first scientist
to study the internal regulation
of the body, and his work was to
lead to the modern concept of
homeostasis—the mechanism
by which the body maintains
a stable internal environment
while the external environment
changes. Bernard studied the
roles of the pancreas and liver
in digestion, and described how
chemicals are broken down into
simpler substances only to be
built up again into the complex
molecules needed to make
body tissues. His major work,
An Introduction to the Study of
Experimental Medicine, was
published in 1865.
See also: Louis Pasteur 156–59WILLIAM THOMSON
1824–1907Born in Belfast, physicist William
Thomson became professor of
natural philosophy at Glasgow
University at 22 years old. In 1892,
he was ennobled, and became
Baron Kelvin, after the river that
runs through Glasgow University.
Kelvin viewed physical change as
fundamentally a change in energy,
and his work produced a synthesis
of many areas of physics. He
developed the second law of
thermodynamics and established
the correct value for “absolute
zero,” the temperature at which all
molecular movement ceases, at
–459.6°F (–273.15°C). The Kelvin
scale, which starts at 0 at absolute
zero, is named after him. Heinvented the mirror galvanometer
to receive faint telegraph signals,
and presided over the laying of the
transatlantic cable in 1866. He
also invented an improved
mariner’s compass and a tide-
predicting machine. Lord Kelvin
often courted controversy, rejecting
Darwin’s theory of evolution and
making many bold statements—
including the prediction that “no
aeroplane will ever be practically
successful,” made one year before
the Wright brothers’ first flight in- However, a quote widely
attributed to Lord Kelvin stating
that “there is nothing new to be
discovered in physics now” is
almost certainly apocryphal.
See also: James Joule 138 ■
Ludwig Boltzmann 139 ■
Ernest Rutherford 206–213
JOHANNES VAN
DER WAALS
1837–1923Dutch physicist Johannes van
der Waals made a significant
contribution to the field of
thermodynamics with his 1873
doctoral thesis, in which he showed
that there is a continuity between
a liquid and gaseous state at a
molecular level. Van der Waals
showed not only that these two
states of matter merge into one
another, but also that they should
be considered as essentially
of the same nature. He postulated
the existence of forces between
molecules, which are now called
the van der Waals forces, and
which explain properties of
chemicals such as their solubility.
See also: James Joule 138 ■
Ludwig Boltzmann 139 ■
August Kekulé 160–65 ■
Linus Pauling 254–59JEAN-DANIEL COLLADON
1802–1893
Swiss physicist Jean-Daniel
Colladon demonstrated that light
could be trapped by total internal
reflection inside a tube, allowing it
to travel along a curved path—a
core principle behind modern-day
optical fibers. In experiments
conducted on Lake Geneva,
Colladon demonstrated that sound
travels four times more quickly
through water than through air. He
transmitted sound through water
over a distance of 30 miles (50km),
and proposed using this method
as a means of communicating
across the English Channel. He
also conducted important work in
the field of hydraulics, studying the
compressibility of water.
See also: Léon Foucault 136–37
JUSTUS VON LIEBIG
1803–1873
The son of a chemical manufacturer
in Darmstadt, Germany, Justus
von Liebig conducted his first
chemistry experiments as a child
in his father’s laboratory. He
grew up to become a charismatic
professor of chemistry whose
laboratory-based teaching methods
were hugely influential. Von Liebig
discovered the importance of
nitrates to plant growth and
developed the first industrial
fertilizers. He was also interested
in the chemistry of food and
developed a manufacturing process
to produce beef extracts. The
company he founded, the Liebig
Extract of Meat Company, would
later produce the trademarked
Oxo stock cubes.
See also: Friedrich Wöhler 124–25