an Autograph Manuscript by Sir Isaac Newton. 65 



pum Cantabrigiensem venisset, ea locutum quae alienationem 

 mentis indicarent ; deinde ab amicis cura ejus suscepta, domoque 

 clausa, remedia volenti noleriti adhibita, quibus jam sanitatem 

 recuperavit, et jam nunc librum suum Principiorum intelligere 

 incipiat." Upon this note the following observations are made 

 by M. BIOT : " II parait d'apres ces details que Ton ne saurait 

 guere douter du fait meme, c'est a dire, que cette tete qui pen- 

 dant tant d'annees s'etait appliquee continumerit a des contem- 

 plations si profondes quelles etaient comme la derniere limite 

 de la raison humaine, se serait enfin troublee elle-meme par 

 1'exces de ses efforts, ou par la douleur d'en voir les resultats 

 aneantis." 



The misfortune here alluded to by HUYGENS and M. BIOT, is 

 the well known anecdote of the loss caused by his dog Diamond ; 

 and it is to this circumstance principally that M. BIOT ascribes 

 the mental derangement under which he supposes NEWTON to 

 have laboured. He adds, " Mais ce fait, d'un derangement 

 d'esprit, quelle qu'en puisse etre la cause, expliquerait pourquoi, 

 depuis la publication du livre des Principes en 1687, NEWTON 

 age seulement alors de 45 ans, n'a plus donne de travail nouveau 

 sur aucune partie des sciences, et s'est con ten te de faire connaitre 

 ceux qu'il avait compose long-temps avant cette epoque, en se 

 bornant a les completer dans les parties qui pouvaient avoir 

 besoin de developpemens." M. BIOT supposes, that after this 

 period of NEWTON'S life, he almost ceased to think on scientific 

 subjects, and that religious reading formed his most habitual 

 occupation ; and he states, that after the " fatal epoch," as he 

 terms it, of 1693, only three really new scientific productions 

 appeared from his hand, one of which had been probably pre- 

 pared for a long time previously, and the others had cost him 

 very little time. 



It is not the object of the present notice to disprove the as- 

 sertion that Sir ISAAC NEWTON was at one period of his life in a 



VOL. XII. PART I. I 



