Notice concerning an Autograph Manuscript by Sir ISAAC NEW- 

 TON, containing some Notes upon the Third Book of the Prin- 

 cipia, and found among the Papers of Dr DAVID GREGORY, 

 formerly Savilian Professor of Astronomy in the University of 

 Oxford. By JAMES CRAUFURD GREGORY, M.D., F.R.S.E., 

 Fellow of the Royal College of Physicians of Edinburgh. 



(Read March 2. 1829J 



AN opinion has been entertained by some of the modern French 

 philosophers, and, among others, by the late celebrated Marquis 

 de LA PLACE, that it was only when far advanced in years that 

 Sir ISAAC NEWTON turned his attention to the study of Theology ; 

 and it has been lately assumed by M. BIOT, in an account of 

 NEWTON and his discoveries, contained in the " Biographic Uni- 

 verselle," as a fact which can scarcely be doubted, that, at one 

 period of his life, he was actually in a state of mental derange- 

 ment. 



The only evidence adduced in support of this remarkable as- 

 sertion is the following note, said to have been written by HUY- 

 GENS, and communicated to M. BIOT by M. VAN SWINDEN : 

 " Die 29 Maii 1 694. Narravit mihi D. COLIN, Scotus, virum ce- 

 leberrimum ac rarum geometram ISAACUM NEWTONUM incidisse 

 in phrenitin abhinc anno et sex mensibus. An ex nimia studii 

 assiduitate, an dolore infortunii, quod in incendio, laboratorium 

 chemicum et scripta queedam amiserat ? Cum ad Archiepisco- 



