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.
NEWTON, ISAAC (b. Woolsthorpe, England,
25 December 1642; d. London, England, 20 March
1727), mathematics, dynamics, celestial mechanics,
astronomy, optics, natural philosophy.
Optics.
on the other hand, understandably thought that he
deserved more credit for his own contributions—including
hypothesis-based explanations—than
Newton was willing to allow him.83 Newton ended the
resulting correspondence on a conciliatory note when
he wrote in a letter of 5 February 1676, “What
Des-Cartes did was a good step. You have added
much in several ways, and especially in taking the
colours of thin plates into philosophical consideration.
If I have seen further it is by standing on the shoulders
of Giants.”84
The opening of Newton's original letter on optics
suggests that he began his prism experiments in 1666,
presumably in his rooms in Trinity, but was interrupted
by the plague at Cambridge, returning to this
topic only two years later. Thus the famous eighteen
months supposedly spent in Lincolnshire would
mark a hiatus in his optical researches, rather than
being the period in which he made his major discoveries
concerning light and color. As noted earlier, the
many pages of optical material in Newton's manuscripts85
and notebooks have not yet been sufficiently
analyzed to provide a precise record of the development
of his experiments, concepts, and theories.
The lectures on optics that Newton gave on the
assumption of the Lucasian chair likewise remain only
incompletely studied. These exist as two complete,
but very different, treatises, each with carefully drawn
figures. One was deposited in the University Library,
as required by the statutes of his professorship, and
was almost certainly written out by his roommate,
John Wickins,86 while the other is in Newton's own
hand and remained in his possession.87 These two
versions differ notably in their textual content, and
also in their division into “lectures,” allegedly given
on specified dates. A Latin and an English version,
both based on the deposited manuscript although
differing in textual detail and completeness, were
published after Newton's death. The English version,
called Optical Lectures, was published in 1728, a year
before the Latin. The second part of Newton's
Latin text was not translated, since, according to the
preface, it was “imperfect” and “has since been
published in the Opticks by Sir Isaac himself with
great improvements.” The preface further states that
the final two sections of this part are composed “in a
manner purely Geometrical,” and as such they differ
markedly from the Opticks. The opening lecture
(or section 1) pays tribute to Barrow and mentions
telescopes, before getting down to the hard business
of Newton's discovery “that ... Rays [of light] in
respect to the Quantity of Refraction differ from one
another.” To show the reader that he had not set forth
“Fables instead of Truth,” Newton at once gave
“the Reasons and Experiments on which these things
are founded.” This account, unlike the later letter in
the Philosophical Transactions, is not autobiographical;
nor does it proceed by definitions, axioms, and
propositions (proved “by Experiment”), as does the
still later Opticks.88
R. S. Westfall has discussed the two versions of the
later of the Lectiones opticae, which were first published
in 1729;89 he suggests that Newton eliminated from
the Lectiones those “parts not immediately relevant
to the central concern, the experimental demonstration
of his theory of colors.” Mathematical
portions of the Lectiones have been analyzed by
D. T. Whiteside, in Newton's Mathematical Papers,
while J. A. Lohne and Zev Bechler have made
major studies of Newton's manuscripts on optics.
The formation of Newton's optical concepts and
theories has been ably presented by A. I. Sabra; an
edition of the Opticks is presently being prepared by
Henry Guerlac.
Lohne finds great difficulty in repeating Newton's
“experimentum crucis,”90 but more important, he has
traced the influence of Descartes, Hooke, and Boyle
on Newton's work in optics.91 He has further found
that Newton used a prism in optical experiments
much earlier than hitherto suspected—certainly before
1666, and probably before 1665—and has shown that
very early in his optical research Newton was
explaining his experiments by “the corpuscular
hypothesis.” In “Questiones philosophicae,” Newton
wrote: “Blue rays are reflected more than red rays,
because they are slower. Each colour is caused by
uniformly moving globuli. The uniform motion which
gives the sensation of one colour is different from the
motion which gives the sensation of any other
colour.”92
Accordingly, Lohne shows how difficult it is to
accept the historical narrative proposed by Newton
at the beginning of the letter read to the Royal Society
on 8 February 1672 and published in the Philosophical
Transactions. He asks why Newton should have been
surprised to find the spectrum oblong, since his
“note-books represent the sunbeam as a stream of
slower and faster globules occasioning different
refrangibility of the different colours?” Newton must,
according to Lohne, have “found it opportune to let
his theory of colours appear as a Baconian induction
from experiments, although it primarily was deduced
from speculations.” Sabra, in his analysis of Newton's
narrative, concludes that not even “the ‘fortunate
Newton’ could have been fortunate enough to have
achieved this result in such a smooth manner.” Thus
one of the most famous examples of the scientific
method in operation now seems to have been devised