( * 55 ) 
Point D, and the Points C and S, two of thole that 
were given, and let the Interfedtions of the Line re- 
volving about D, with thofe that revolve about G 
and S, be carried over the given Right Lines A E, 
C F-, and the Interfe&ion of thofe that revolve a- 
bout C and S with each other, will, in the mean 
Time, defcribe a Conick Sedtion, that lliall pafs 
through the five given Points A, F, C, S and E. 
It is then fhewn, that when C, S and D are taken 
in the lame Right Line, the Point P defcribes a Right 
Line as alfo when C, S and A are in the fame 
Right Line ; which allb follows from what is de- 
mon (Ira ted in that very ingenious Paper concerning 
‘Pappus’s Porifms, communicated by Mr. Sympfon , 
ProfelTor of Mathematicks at Glafgovj publilhed in 
the Phil. Tranf. N°. 3 77. 
In the next Place it is Ihewn, that if four Right 
Lines revolve about four Poles C, S, D and E, and 
thofe that revolve about D and E, ferve only to 
guide thofe that revolve about C and S ; fo that Q, 
and R, the Interfecbions of that which revolves a- 
bout D, with thofe that revolve about E and S, be 
carried over the fixed Lines A B and A F ; and M the 
U ^ Inter- 
