3 £8 Mr. JelTop to Mr. Willughby. 



many other Birds, being fo general as it is - y and thd 

 Cut doth fomcthing referable it, altho' not exa&Iy. 



I have bgen labouring all this Day to fend you the 

 Problem you fpeak of, but find it too long and difficult 

 to difpatch it fo foon > for I had committed very lit- 

 tle of it to writing, and am not fo confident of the 

 Succefs of it, that I dare fend it thus imperfe&j there 

 being a great many Propofitions to be demonftrated 

 before I can come to the thing I aim at. All that I 

 can certainly promife is this, akho' I have been a little 

 more bold than wife. 



Si conns re£ius fecetur a piano axi parallelo, de- 

 mittantur dute re£l<z ayertice ejufdem toni, ad terminos 

 bafes hyperbolae per earn feffiioncm fattse, invenire quadra- 

 turn tequale fuperficiei conictf a lined hyper 'bolted £5? iifdem 

 reUis terminate. And after this to find a conical Su- 

 perficies equal to an Hyperbole, which fhail cut the 

 Axis of a Cone $ and another conical Superficies (all 

 of them fomething after the fame Manner) equal to a 

 Triangle, lefs by an Hyperbole. And I fancy that 

 I have found out the Ratio that fome of thefe feveral 

 Sorts of conical Superficies have one to another. 

 Whether thefe things are ordinary or no, I know not : 

 But however the main Defign fucceed, I find this, 

 which is a little furprizing unto one who is not much 

 verfed in thefe Matters, that it is poflible to find a 

 plain Figure equal to any Part of the Superficies of a 

 Cone cut oft after any manner by Planes : It is alfo 

 poflible a plane Figure being given, however termi- 

 nated after any manner by thofe ordinary Lines ufed 

 by Geometricians, to find a Part of the Superficies 

 of a Cone equal to it. You may alfo find in a Cone 

 cut by an Ellipfts an Ungula, to which you may find 

 a Pyramide equal, as well as in the Cylinder, befides 

 a great many other Portions of a Cone, to which the 

 like may be done more eafily } but that which I molt 

 take notice of is this, viz. 



Sir 



