On the Axial Involution of a Net of Conics and its Associated (1,2)

In every net of conics

N : c₁S₁ + c₂S + 0S = 0

where S₁, S₂, and S₃ are ternary quadratics in point or line co-ordinates, and the e's are constants, there is in general a unique member which has a given line u for a principal axis. It follows, therefore, that the two principal axes of conies of the net are co-lines in a Cremona lineinvolution in the plane.