Electronic edition published by Cultural Heritage Langauge Technologies (with permission from Charles Scribners and Sons) and funded by the National Science Foundation International Digital Libraries Program. This text has been proofread to a low degree of accuracy. It was converted to electronic form using data entry.
PLAYFAIR, JOHN (b. Benvie, near Dundee,
Scotland, 10 March 1748; d. Edinburgh, Scotland,
20 July 1819), mathematics, physics, geology.
Playfair was the eldest son of the Reverend James
Playfair. At the age of fourteen he went to the
University of St. Andrews, primarily to qualify for the
ministry, but he also showed remarkable mathematical
ability. In 1769 he left St. Andrews for Edinburgh. On
the death of his father in 1772, he succeeded him in the
living of Benvie, which he resigned in 1782 to become
tutor for a private family. From 1785 to 1805 Playfair
held a professorship of mathematics at the University
of Edinburgh. He edited the Transactions of the Royal
Society of Edinburgh for many years, and most of his
papers appeared in that periodical. They were
concerned almost entirely with mathematics, physics,
and biographies. His Elements of Geometry was
published in 1795. Following the death in 1797 of his
friend James Hutton, Playfair proceeded to make a
careful analysis, clarification, and amplification of
Hutton's Theory of the Earth, which had originally
been presented as a paper read in 1785 to the Royal
Society of Edinburgh and was expanded into the
two-volume work of 1795. Playfair's efforts resulted in
Illustrations of the Huttonian Theory of the Earth
(1802). In 1805 he became professor of natural
philosophy at Edinburgh, where his lectures now
embraced physics and astronomy. His Outlines of
Natural Philosophy was published in 1814.
Playfair's professional work was thus in mathematics
and physics. His book on geometry is a full
presentation of the first six books of Euclid, with much
additional material. The formal treatment of linear
parallelism requires axioms. Finding Euclid's axioms
on this matter to be unsatisfactory, Playfair proposed
“that two straight lines, which intersect one another,
cannot be both parallel to the same straight line.”
This is what became known as “Playfair's axiom,” as
it is given in his Elements of Geometry.
Playfair's fame as a scientist, however, rests almost
entirely on his work in geology--hardly a “professional”
study at the time--in presenting Hutton's
momentous theory in a clear and palatable form
(which Hutton himself had failed to do), and in adding
materially to the geological knowledge of the time.
The precision and elegance of the style of his mathematical
exposition is here applied to a descriptive,
inductive science. As Archibald Geikie remarked
(1905): “How different would geological literature be
to-day if men had tried to think and write like
Playfair!” The publication of the Illustrations is indeed
one of the most conspicuous landmarks in the progress
of British geology. It ended the early period in the
history of that science, a termination that happened to
coincide with the end of the eighteenth century. There
was a pause in the advance of geology during the early
years of the nineteenth century; but powerful forces
were gathering an impetus that was released in the
second decade with the publication of important works
by William Smith, John Farey, and Thomas Webster,
which were summarized in the next landmark of the
literature, Conybeare and Phillips' Outlines of the
Geology of England and Wales (1822). Playfair lived
well into this second period of activity but did not take
any part in it. A project that was very much in his
mind was the preparation of a comprehensive work on
geology, which was to have been a greatly amplified
edition of his Illustrations. The peace of 1815 enabled
Playfair to make an extensive tour of France, Switzerland,
and Italy, in order to extend his observations for
this purpose; but although we have details of the
journey, nothing of the projected work was composed.