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 GREGORY,
JAMES, whose valuable discoveries served so much to accelerate the
progress of the mathematical and physical science in the seventeenth
century, was born in 1638, at Drumoak in Aberdeenshire, where his father,
the reverend John Gregory, was minister. Little is known of James Gregory’s
father, but from some slight notice of him in the Minutes of the General
Assembly; and whatever part of the genius of the subject of this memoir
was possessed by inheritance seems to have descended from the mother. It
is an observation of a distinguished philosopher of the present day, Dr
Thomson, that, "he never knew a man of talent whose mother was not a
superior woman;" and a more happy instance of the truth of this
remark could not be found than that of James Gregory. Mrs Gregory seems to
have descended from a family of mathematicians. Her father was Mr David
Anderson of Finghaugh, whose brother, Alexander Anderson, was professor of
mathematics (about the beginning of the seventeenth century,) in the
university of Paris, and he himself was long noted for his application to
mathematical and mechanical subjects. The reverend John Gregory died when
the subject of this article was yet in his boyhood, and left the care of
the education of James to David, an elder brother, and the surviving
parent. The mother having observed the expanding powers of his mind, and
their tendency to mathematical reasoning, gave these early indications of
his genius all possible encouragement, by instructing him herself in the
elements of geometry. Having received the rudiments of his classical
education at the grammar school of Aberdeen, he completed the usual course
of studies at Marischal college. For a considerable time after leaving the
university, James Gregory devoted his attention to the science of optics.
The celebrated French philosopher Descartes had published his work on
Dioptrics the year before Gregory was born, nor had any advances been made
in that science until James Gregory published the result of his labours in
a work printed at London in 1663, entitled, "Optics Promoted, or the
mysteries of reflected and refracted rays demonstrated by the elements of
geometry; to which is added, an appendix, exhibiting a solution of some of
the most difficult problems in astronomy." In this work, which forms
an era in the history of the science of that century which its author so
eminently adorned, and which was published when he was only twenty-four,
there was first given to the world a description of the reflecting
telescope, of which Gregory is the indisputable inventor. He proposed to
himself no other advantage from using mirrors instead of glasses in the
construction of telescopes, than to correct the error arising from the
spherical figure of the lenses, and by forming the reflectors of a
parabolic figure, to bring the rays of light into a perfect focus, being
ignorant of the far greater error arising from the unequal refrangibility
of the rays of light, which it was reserved for Newton afterwards to
discover. Gregory went to London a year after the publication of his work
on optics, with a view to the construction of his telescope, and was
introduced to Mr Rieves, an optical instrument maker, by Mr Collins,
secretary to the Royal Society. Rieves could not finish the mirrors on the
tool so as to preserve the figure, and so unsuccessful was the trial of
the new telescope that the inventor was deterred from making any farther
attempts towards its improvement, nor were these reflectors ever mounted
in a tube. Sir I. Newton objected to this telescope, that the hole in the
centre of the large speculum would be the cause of the loss of so much
light, and invented one in which this defect was remedied. The Gregorian
form is universally preferred to the Newtonian, when the instrument is of
moderate size, the former possessing some material advantages; yet the
latter was always employed by Dr Herschel, in those large instruments, by
which the field of discovery has, of late, been so much extended. Although
the inventor of the reflecting telescope has received all the honour which
posterity can bestow, yet it is lamentable to think that he never had the
satisfaction of seeing an instrument completed in his own lifetime. It is
only necessary to remark farther, on this subject, that some papers of
great interest passed between Gregory and Sir Isaac Newton, concerning the
reflecting telescope, which may be consulted with advantage by those who
would wish to investigate the subject. His work on optics contains,
besides the discovery of the reflecting telescope, that of the law of
refraction. Descartes had made a similar discovery long ere this, but
Gregory had not heard of it till his own work was ready for publication -
to which circumstance he alludes in his preface. Playfair, in considering
this subject, very justly remarks, that "though the optics of
Descartes had been published twenty-five years, Gregory had not heard of
the discovery of the law of refraction, and had found it out only by his
own efforts;—happy in being able, by the fertility of his genius, to
supply the defects of an insulated and remote situation." [Playfair’s
Dissertation, in the Supplement to the Encyclopedia Britannica, part 1st,
page 25, 6th edition.] The method in which Gregory investigated
the law of refraction is truly remarkable, not only for its singular
elegance, but originality, and the series of experiments which he
instituted for the purpose of demonstration, affords an indelible proof of
the accuracy of his observations. It is truly remarkable, that the
calculations by this law differ so little from those obtained by the most
accurate experiments. There is yet another discovery of the very highest
importance to the science of astronomy, which is falsely and, we would
hope, unknowingly attributed to another philosopher, whose manifold
brilliant discoveries throw an additional lustre over the country which
gave him birth. We allude to the employment of the transits of Mercury and
Venus, in the determination of the sun’s parallax, the merit of which is
always ascribed to Dr Halley, even by that eminent astronomer Laplace. But
it is plainly pointed out in the scholium to the 28th proposition of
Gregory’s work, published many years prior to Halley’s supposed
discovery. The university of Padua was at this time in high repute for
mathematical learning, and Gregory repaired thither from London, about the
end of 1667, for the purpose of prosecuting his favourite study. Here he
published a Latin work on the areas of the circle and hyperbola,
determined by an infinitely converging series; a second edition of which
he afterwards published at Venice, with an appendix on the transmutation
of curves. Mr Collins, who always showed himself zealous in Gregory’s
favour, introduced this work to the notice of the Royal Society of London,
of which he was secretary. This work received the commendation of that
distinguished nobleman lord Brounker, and Dr Wallis, the celebrated
inventor of the arithmetic of infinites. Gregory’s attention was once
more drawn to the squaring of curves, by the method of converging series,
on account of receiving an instance of the case of the circle in a letter
from his friend Collins, who informed him that Newton had discovered a
general method for all curves, mechanical and geometrical. Gregory
speedily returned to Collins a method for the same purpose, which he was
advised by his brother David to publish. Gregory refused to do this, and
that from the most honourable motive: as Newton was the original inventor,
he deemed it unfair to publish it, until Sir Isaac should give his method
to the public. Soon after, he returned to London, and from his celebrity
as a mathematician, he was chosen a fellow of the Royal Society. He read
before the society, the account of a dispute in Italy concerning the
motion of the earth, which Riciolli and his followers had denied, besides
many other valuable communications. Huygens had attacked Gregory’s
method of quadrature in a journal of that period, to which he replied in
the Philosophical Transactions. The dispute was carried on with great
warmth by both, and from Gregory’s defence it would appear he was a man
of warm temperament, but acute and penetrating genius. Of the merits of
either, in this dispute, it would be out of place here to enter into
detail. Leibnitz, who considered the subject with attention, and whose
capacity of discernment in such matters cannot be questioned, is of
opinion, that although Huygens did not point out errors in the work of
Gregory, yet he obtained some of the results by a much simpler method.
The small work "Exercitationes
Geometricae," published by Gregory at London in 1668, consisted of
twenty-six pages, containing however a good deal of important matter.
Nowhere do we learn more of the real private character of Gregory than in
the preface and appendix to this little work. He speaks in explicit terms
of his dispute with Huygens, complains of the injustice done him by that
philosopher and some others of his contemporaries; and we are led to
conclude from them, that he was a man who, from a consciousness of his own
powers, was jealous of either a rival or improver of any invention or
discovery with which he was connected. The same year in which he published
this last work, he was chosen professor of mathematics in the university
of St Andrews. The year following he married Miss Mary Jamieson, daughter
of Mr George Jamieson, the painter whom Walpole has designated the Vandyke
of Scotland. By his wife he had a son and two daughters. The son, James,
was grandfather of Dr Gregory, author of the "Theoretiem Medicinae,"
and professor of the theory of medicine in the university of Edinburgh.
James Gregory remained at St Andrews for six years, when he was called to
fill the mathematical chair in the university of Edinburgh. During his
residence at St Andrews, he wrote a satire on a work of Mr George Sinclair’s,
formerly professor of natural philosophy in Glasgow, but who had been
dismissed on account of some political heresies. Dr Gregory did not live
to enjoy the chair in Edinburgh more than one year; for returning home
late one evening in October, 1675, after showing some of his students the
satellites of Jupiter, he was suddenly struck blind, and three days
afterwards expired. Thus, at the early age of thirty-seven, in the vigour
of manhood, was put a melancholy termination to the life of James Gregory.
Of the character of this great man little can be said. His knowledge of
mathematical and physical science was very extensive; acuteness of
discrimination and originality of thought are conspicuous to all his
works; and he seems to have possessed a considerable degree of
independence and warmth of temper.
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