52 Britain's Heritage of Science 



reflecting telescope which goes by his name, but he had no 

 opportunity of actually constructing an instrument. He 

 was also the first to show how the distance of the sun 

 could be deduced by observations of the passage of Venus 

 across the disc of the sun. After a period of study at Padua 

 he became Professor of Mathematics at St. Andrews and 

 subsequently at Edinburgh. His elder brother, David Gregory 

 (1627-1720), was privately engaged in scientific pursuits, 

 and having used a barometer to predict the weather, paid 

 the penalty of his success by being accused of witchcraft. 

 David had three sons, the eldest of whom (1661-1708) 

 successively held the Chair of Mathematics at Edinburgh 

 and the Savilian Professorship of Astronomy at Oxford ; 

 the second son succeeded his elder brother in the Chair of 

 Mathematics at Edinburgh, and the third (Charles) was 

 Professor of Mathematics at St. Andrews. The eldest son 

 of David, the Savilian Professor, was Dean of Christ Church 

 and Professor of Modern History at Oxford. 



Among the descendants of James Gregory we find in 

 three generations four distinguished medical men, all of 

 whom held professorships in the subject, and in the fourth 

 generation, two brothers, the elder of whom, William (1803- 

 1858), became Professor of Chemistry at the Andersonian 

 University in Glasgow, at King's College in Aberdeen, and 

 finally at Edinburgh University. His younger brother, 

 Duncan Farquharson Gregory, entered Trinity College, 

 Cambridge, assisted for a time the Professor of Chemistry, 

 but ultimately devoted his attention to mathematics, and 

 founded the Cambridge Mathematical Journal. 



The scientific activity of the Universities in the second 

 half of the seventeenth century was naturally dominated 

 by the influence of Newton's work. His dynamical investi- 

 gations, leading up to the explanation of the observed motions 

 in the solar system, have already been described, and it 

 is interesting to trace the historical connexion between 

 those discoveries and others which remain to be mentioned. 

 Fortunately his own words describing the succession of 

 ideas as they occurred to him have been preserved : 



" In the beginning of the year 1665 I found the 



method of approximating series and the rule for deducing 



