GREGORY. 



" Geometric Pars Universalis, inserviens 

 Quantitatum Curvarum, Transmutationi 

 et Mensurae;" in which he is allowed to 

 have shewn, for the first time, a method 

 for the transmutation of curves. These 

 works engaged the notice, and procured 

 the author the correspondence, of the 

 greatest mathematicians of the age, New- 

 ton, Huygens, Wallis, and others. An 

 account of this piece was also read be- 

 fore the Royal Society, of which Mr. 

 Gregory, being returned from his travels, 

 was chosen a member the same year, and 

 communicated to them an account of the 

 controversy in Italy about the motion of 

 the earth, which was denied by Riccioli, 

 und his followers. Through this channel, 

 in particular, he carried on a dispute with 

 M. Huygens, on the occasion of his trea- 

 tise on the quadrature of the circle and 

 hyperbola, to which that great man had 

 started some objections ; in the course of 

 which our author produced some im- 

 provements of his series. But in this 

 dispute it happened, as it generally does 

 on such occasions, that the antagonists, 

 though setting out with temper enough, 

 yet grew too warm in the combat. This 

 was the case here, especially on the side 

 of Gregory, whose defence was, at his 

 own request, inserted in the Philosophi- 

 cal Transactions. It is unnecessary to 

 enter into particulars: suffice it there- 

 fore to say, that, in the opinion of Leib- 

 nitz, who allows Mr. Gregory the high- 

 est merit for his genius and discoveries, 

 M. Huygens has pointed out, though not 

 errors, some considerable deficiencies in 

 the treatise above-mentioned, and shown 

 a much simpler method of attaining the 

 same end. 



In 1688, our author published at Lon- 

 don another work, entitled " Exercita- 

 tiones Geometries," which contributed 

 still much further to extend his reputa- 

 tion. About this time he was elected 

 Professor of Mathematics in the Univer- 

 sity of St. Andrews, an office which he 

 held for six years. During his resi- 

 dence there he married, in 1669, Mary, 

 the daughter of George Jameson, the 

 celebrated painter, whom Mr. Walpole 

 has termed the Vandyke of Scotland, and 

 who was fellow-disciple with that great 

 artist in the school of Rubens, at An- 

 twerp. 



In 1672, he published " The great and 

 new Art of weighing Vanity : or a Dis- 

 covery of the Ignorance and Arrogance 

 of the great and new Artist, in the pseu- 

 do-philosophical Writings. By M. Pa- 

 trick Mathers, Archbedal to the Univer- 



VOL. VI. 



sity of St. Andrews To which are an- 

 nexed some Tentamina de Motu Penduli 

 et Projectorum." Under this assumed 

 name, our author wrote this little piece, 

 to expose the ignorance of Mr. Sinclare, 

 professor at Glasgow, in his hydrostatical 

 writings, and in return for some ill usage 

 of that author to a colleague of Mr. Gre- 

 gory's. The same year Newton, on his 

 wonderful discoveries in the nature of 

 light, having contrived a new reflecting 

 telescope, and made several objections to 

 Mr Gregory's, this gave birth to a dis- 

 pute between those two philosophers, 

 which was carried on during this and the 

 following year, in the most amicable man- 

 ner, on both sides ; Mr. Gregory defend- 

 ing his own construction, so far as to give 

 his antagonist the whole honour of hav- 

 ing made the catoptric telescopes prefer- 

 able to the dioptric, and showing that the 

 imperfections in these instruments were 

 not so much owing to a defect in the ob- 

 ject speculum, as to the different refran- 

 gibility of the rays of light. In the course 

 of this dispute our author described a 

 burning concave mirror, which was ap- 

 proved by Newton, and is still in good 

 esteem. Several letters that passed in- 

 this dispute are printed by Dr. Desagu- 

 liers, in an appendix to the English edi- 

 tion of Dr. David Gregory's " Elements 

 of Catoptrics amd Dioptrics." 



In 1674, Mr. Gregory was called to 

 Edinburgh, to fill the chair of mathema- 

 tics in that university. This place he 

 had held but little more than a year, when, 

 in October 1675, being employed in 

 shewing the satellites of Jupiter through 

 a telescope to some of his pupils, he was 

 suddenly struck with total blindness, and 

 died a few days after, to the great loss of 

 the mathematical world, at only 37 years 

 of age. 



As to his character, Mr. James Grego- 

 ry was a man of very acute and penetrat- 

 ing genius. His temper seems to have 

 been warm, as appears from his conduct 

 in the dispute with Huygens : and, con- 

 scious perhaps of his own merits as a dis- 

 coverer, he seems to have been jealous 

 of losing any portion of his reputation by 

 the improvements of others upon his in- 

 ventions. He possessed one of the most 

 amiable characters of a true philosoper, 

 that of being content with his fortune in 

 his situation. But the most brilliant part 

 of his character is that of his mathemati- 

 cal genius as an inventor, which was of 

 the first order ; as will appear by the fol- 

 lowing list of his inventions and discove- 

 ries. Among many others may be reck- 

 K 



