26 . 



The curves q' resting on a straight line /, are represented by the 

 generatrices of the cone that projects the curve ^' out of M'. As 

 this cone is cut by a /u' in nine points, the curves q)' intersected 

 by / form a surface ./'. On this surface a^,a,,a, and 0' are three- 

 fold lines, because any straight line tki and any line t cuts the 

 cone (M' , )^) three times and the image of the double generatrix of 

 this cone is a double curve of A\ Any curve of [(>'] has 8X3 

 points in common with A* on the singular lines; hence M is a 

 triple point of A\ 



