Mifceltanea Curio fa. ^ 



2* That they will all have one common Cen- 

 ter, viz. the Center or Pole of Proje&ion. 



That their common Center, viz,, the 

 Centre of Proje&ion, will be their common 

 Pole. 



4. That their Radij or Semi- Fig. 1. 

 diameters will be equal to the 

 Semi-tangent of their Diftance from the remo- 

 te? Pole of Projedtion. 



For in Figure 1. fuppofing e the Eye, ab 

 the Plain of Proje&ion, p its remoter Pole, 

 and mn the Circle to be proje&ed oc equal 

 to q, will be equal to the Semi-tangent of mp 

 or p», the Diftance of the Circle mn from p th@ 

 remoter Pole. 



LEMMA the lid. 



If an inclined Cone be cut with a Plain not 

 parallel to the Bafe, yet fo that it cuts off a 

 Part fimilar to the whole, the Se&ion made in 

 the Superficies of the Cone fhall be a Circle. 



Whence it follows. 



1 . That all Circles whatfoevcr ( except 

 fuch as lie in the fame Plain with the Eye, and 

 which have been already confidered) thothey 

 are not parallel to the Periphery of the Plain 

 of Proje&ion, yet become Circles in the Pro- 

 jection. 



For if, as before, e reprefents Fig. 2, 3,4; 

 the Place of the Eye, ab the Plain 

 of Proje&ion, p its remoter Pole, and mn the 

 Circle to be proje&ed. 



Through 



