144 



CORRESPONDANCE. 1 664. 



Ns 1272. 



W. Brouncker à Christiaan Huygens. 



[novembre 1664]. 



Appendice IV au No. 1268. 



La lettre se trouve à Leiden, coll. Huygens, 



de Milord Brouncker. 1664 ')• 



") According to my Principle, which agrées well with 

 the few Experiments j haue made of that kind, a Pendu- 

 lum ifochrones to any line or plain, or folidgiuen equals 

 the diftance from the Vertex of the horizontal plaine paf- 

 fing the Center of Grauity of that plaine or folid which 

 is made of the horizontal parts of the giuen line, plain or 

 folid multiplied into the diftance from the Vert,ex ^). 



For Example AB being a line giuen, the triangle 



ABC is the plain fo made and AD is the diftance from the 



Vertex A of the horizontal plaine ED paffing the Center 



of grauity f, which is therefore the Altitude of the Pen- 



dulum ifochrone to the line AB (AD ■=: | AB). And fo a Pendulum ifochronc 



to a rightline triangular plaine is |- of the Altitude of the triangle &c. 



This pray prefent to Monfieur de Zulichem with my very humble feruice & 

 thanks for what he bas been pleafd to communicate; and afTure him of a very 

 acceptable réception of as much more as he fhall think fit to oblige me with. 



") Sa théorie n'eft pas vraye , fi non dans l'agitation des figures planes fur un axe 

 qui eft dans leur mefme plan, mais dans les folides elle eft entièrement faufile, 

 [Chr. Huygens]. 



*) Methodus indiuifibilium. [Chr. Huygens]. 



') Ces mots sont de la main de Chr. Huygens. 



