discovery named 'oxygen'
As luck would have it, Lord Shelburne was setting off
on a trip to the continent, and took Priestley along.
In France, Priestley met Lavoisier and described his
discovery. It turned out to be the clue Lavoisier needed
to develop his theory of chemical reactions the
"revolution" in chemistry that would finally dispel
the phlogiston theory. Burning substances, Lavoisier
argued, did not give off phlogiston; they took on Priestley's
gas, which Lavoisier called "oxygen" from the Greek
By then, however, Priestley had returned to England,
where he escalated his support for the American revolution
and for highly unorthodox religious views. Those positions
were a source of embarrassment for Lord Shelburne. Priestley
left his service in 1780, moving to Birmingham and taking
a position as head of a liberal congregation called
His new location brought him into contact with numerous
luminaries including Erasmus Darwin, grandfather of
Charles, the great architect of evolutionary theory.
James Watt and Matthew Boulton who were about
to transform society with their steam engine
were there, as was Josiah Wedgwood, the famous potter,
who supported Priestley's chemical experiments. Birmingham
also boasted a distinguished scientific discussion group,
the Lunar Society, which met on nights of a full moon
so that the members could see their way home.
Priestley's encouragement of the French Revolution,
together with his increasingly controversial theology
and attacks on the doctrine of the trinity, eventually
became too notorious for safety. In 1791, an alcohol-fueled
mob of royalists burned the New Meeting house, and then
Priestley's home. The scientist and his family barely
escaped. They fled to London, but eventually it proved
no safer. Priestley's sons could not find work and emigrated
to Pennsylvania, where they hoped to found a center
for free-thinking Englishmen.
Finally Joseph and Mary followed them, setting sail
for America on April 8, 1794. Priestley turned down
the offer of a teaching position at the University of
Pennsylvania in Philadelphia, and instead built a house
in the remote hamlet of Northumberland to be near his
sons. The area was decidedly rustic.
There Priestley continued his research, isolating carbon
monoxide (which he called "heavy inflammable air") and
founding the Unitarian Church in the United States.
For the most part, he led a quiet and reflective lifeespecially
after his friend Thomas Jefferson was elected president
During his final trip to Philadelphia, he told the Philosophical
Society that "having been obliged to leave a country
which has been long distinguished by discoveries in
science, I think myself happy by my reception in another
which is following its example, and which already affords
a prospect of its arriving at equal eminence." His words
proved prophetic. A colloquium held on the centennial
of Priestley's discovery of oxygen led to the founding
of the American Chemical Societytoday the world's
largest scientific societyin 1876.
February 3, 1804, Priestley began an experiment, but
found himself too weak to continue. He went to his bed
in his library, never again to emerge. On February 6,
he summoned one of his sons and an assistant. He dictated
some changes in a manuscript. When he was satisfied
with the revisions, he said "That is right. I have now
done." Minutes later he died painlessly, ending what
Jefferson called "one of the few lives precious to mankind."