14 
GREGORY. 
and procured the author the correfpondence, of the Optics, 8vo.—the Exercitatio Geometrica of the fame au- 
moft eminent mathematicians of the age, Newton, Huy. thor, 1684, 4to. or his ingenious piece upon PradlicaE 
gens, Halley, Wallis, and others. Ao account of the Geometry. 
piece la ft mentioned was alfo read by Mr. Collins be- GREG'ORY (David), nephew of the preceding,; 
fore the Royal Society, of which our author, upon his and like him a very eminent mathematician, born at 
return from his travels, was chofen a member; foon af- Aberdeen, in 1661. He was-the eldeft -foil of Mr. Da- 
ter which he communicated to that body an account of vid Gregory of Kinnairdie, a gentleman .who had the 
the cOntroverfy carried on in Italy concerning the mo- ftngular fortune to fee all three of his Ibns profeftors of 
tion of the earth, which was denied by Riccioli and his mathematics, at the fame time, in three of the Britilh 
followers; and he alfo enriched the Philofophical Tranf- univerfities, viz. David at Oxford, his fecond fon James’ 
actions by the contribution of other excellent papers. at Edinburgh, and his third fon Charles at St. Andrew’s. 
In 1G68, lord Brounker having produced his Series David became fo diftinguifhed for his proficiency, that 
for Squaring the Hyperbola, a demonftration of it was in 1684, when only in the twenty-third year of his age, 
foon afterwards given by Mr. Mercator, in the Loga- he was eledted profetfor of mathematics in the uni verfity 
rithmo-technia. Thefe papers induced Mr. Gregory, be- of Edinburgh. In the fame year he publiftied, front 
fore the end of the fame year, to publiftt his Exercita- his uncle’s papers, with confiderable and important ad- 
tiones Geometrica, 410. in which he improved and enlarged ditions of his own, Exercitatio Geometrica de Dimenjione Fi- 
Mercator’s difcovery, and gave a geometrical demon- gurartm, Jive Specimen Melhodigeneralis divictiendi quafvis Fi- 
ftration of it by means of futurning up the fecants of a guras, 4to. In this treatife, alfuming the dodtrine of 
Circular.,arch. In this treatife he likewife, for the firft indivifibles, and the arithmetic of infinites, as already 
time, demonftrated the meridian line to be analogous to known and received by geometers as fufficiently de- 
a fcale of logarithmic tangents of the half complements monftrated, he explained a method which not only 
of latitude, and extended his method of infinite feries to fuited his uncle’s examples, left by him without any 
the menfuration of fome mechanical curves, as the con- way of finding them, but difeovered others, by which 
choid and cifloid of the ancients. About this time he an infinite number of curve lines, and the areas contain- 
was appointed profeflor of mathematics in the univer- ed between them and right lilies, might be meafured. 
fity of St. Andrews, .an office which he held for fix He foon perceived the excellence of the Newtonian phi- 
years. During his. refidence'there he married, in the lofophy, and was the firft who had the merit of intro- 
vear 1669, Mary the daughter of George Jamefon, the ducing it into the fchools, by his public ledhires at 
celebrated painter, whom Mr. Walpole has termed the Edinburgh. He continued to fill the mathematical 
Vandyke of Scotland, and who was fellow-difciple with chair at Edinburgh with great applaufe till the year 
that great artift in the fchool of Antwerp. In 1672, 1691, when, on hearing a report of Dr. Bernard’s inten- 
Mr. Gregory publiftied a fmall fatirical tradl, entitled, tion to refign the Savilian profeftorffiip of aftronomy at 
The Great and New Art of Weighing Vanity ; or, a Oxford, he went to London. There he was introduced 
Difcovery of the Ignorance and Arrogance of the Great to fir Ifaac Newton, who foon conceived a high opinion 
and New Artift, in his Pfeudo-philolophical Writings, of his abilities, and recommended him to the Royal So. 
By M. Patrick Mathers, Arch-beadle to the Univer- 
iity of St. Andrews. To which are annexed, fome 
ciety, of which he was chofen a member. Newton alfo 
introduced him to the acquaintance of Mr. Flamfteed, 
Tentamina de Motu Penduli & Projeflorum , 8vo. In this the aftronomer-royal, who concurred in furthering the 
;e, under an aflumed name, he expofed, with much 
keennefs and humour, the ignorance of Mr. Sinclair, a 
defign on which he had come into England. With 
their recommendation he went to Oxford, where, in the 
profelfor of Glafgow, in his hydroftatic writings, who year laft mentioned, he was incorporated in the degree 
jpiuiciiui U1 Uidi-uw, ill HID iij tai uu.cti.iv. niuiiigjj 
wrote againft Mr. Boyle, and behaved ill towards a col¬ 
league of Mr. Gregory. During the fame year, our au¬ 
thor partook in the univerfal aftoniftiment which ftruck 
the learned world upon the firft news of Newton’s dis¬ 
coveries concerning the nature of light; and though he 
was fenfible of the change made by it in every branch 
of M. A. and accumulated thdfe of phyfic ; foon after 
which he was elected to the vacant chair of Savilian 
profelfor of aftronomy, though Mr. afterwards Dr. Hal¬ 
ley was a competitor. Their rivallhip, however, inftead 
of animolity, laid the foundation of .friendlhip between 
thefe eminent men ; and Halley afterwards became the 
evidence on which that great man’s theory was founded 
But as, in confequence of thefe difeoveries, Newton 
had contrived a new refledting telefcope, and made fe- 
of optics, yet he readily yielded to the experimental colleague of Gregory, by obtaining the profelforlhip of 
„ ,:,i—tU«r,rO uja« frmnrtprt geometry in the fame univerfity. In 1693 Dr, Gregory 
publiftied, in the Philofophical TranfaCtions, a refolu- 
___ .. 4 , tion of the Florentine enigmatical problem de tejludine 
veral objections to Mr. Gregory’s, this circumftance vcliformi quadrabili ; and afterwards communicated to the 
gave rife to a controverfy between thefe two philofo- public through the fame channel feveral ingenious jaa- 
phers, which was carried on in the molt amicable man- thematical papers. In 1695 he publiftied at Oxford, 
ner on both fides. In the courfe of this difpute, Mr. Catoptrics & Dioptric# Spheric a Element a, 8vo. which con- 
Gregory fuggefted the firft idea of a burning concave tains the fubftance of fome of his public ledtures, read 
mirror, which w^as approved by Newton, and afterwards eleven years before at Edinburgh. 
came into common ufe among philofophical experimen- 
talifts. Several of the letters that palled in this amica¬ 
ble controverfy were publiftied by Dr. Defaguliers, in 
n appendix t<J the Englifli edition of Dr. David Gre- 
ory’s Elements of Catoptrics and Dioptrics. In 1674, 
Mr. Gregory 
In 1697, Dr. Gregory was the firft who gave to the 
public the demonftration of that curve s wliich is well 
known fince by the name of catcnaria, or that curve 
which is formed by a chain faftened at each end. His 
paper on this curve was inferted in the Philofophical 
Trar"- ‘ " **** ” ~ " 
called to Edinburgh, to fill the ma- Tranfadtions, and in the Mifcellanea CurioJ'a , 
e of the 
thematical chair in that univerfity. This place he had nobleft difeoveries that had at that time been prefented : 
held for little more than a year, when, in Odtober, 
1675, being employed in ftiewing the fatellites of Jupi¬ 
ter through a telefcope to fome of-his pupils, he was 
the Royal Society. It is true that Leibnitz and John 
Bernouiiii foon afterwards laid claim to the merit of 
Having folved the problem at an earlier period than our 
fuddenly ftruck with total blindnefs, and died a few author; but, fince their inventions were communicated 
days afterwards, at the early age of thirty-feven. 
Such of Mr. Gregory’s inventions as are not con. 
tained in his works already enumerated, are the hub- 
jedts of feveral letters and papers printed either in the 
by them without any demonftrations, he maintained his 
right of precedence at leaft on that point. But Dr. 
Gregory’s moft celebrated performance appeared in 
702, entitled, AJtronomia Phyjica & Geometrica Elemmta, 
Philofophical Tranfactions, vol. iii .—theCommercium Epif- folio. This excellent work was written chiefly with 
tolicumy 1715, 8vo.—the appendix to Dr. Defaguliers’s the defign of explaining fir Ifaac Newton’s geometry of 
EngLilh edition of Dr. David Gregory’s Elements of the centripetal forces, us far as his difeoveries in aftro¬ 
nomy 
