View source for Conical net

A [[conjugate net]] on a surface in three-dimensional space formed by the conical lines of the surface, that is, by the tangent lines to the cones circumscribed about the surface. A surface carrying a conical net is called a [[Peterson surface]]. A [[transport net]] can be considered as a special case of a conical net. The vertices of the cones of a conical net are positioned on two curves. Conical nets depend on at most four parameters. Only non-degenerate surfaces of the second order can carry a $4$-parameter family of conical nets. A surface carrying a $2$-parameter family of conical nets is a [[ruled surface]] belonging to a linear congruence (that is, a [[congruence of lines]] which are the common secants of two straight lines).

====References====
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<TR><TD valign="top">[1]</TD> <TD valign="top">  Ya.P. Blank,   "A certain generalization of S. Lie's problem on translation surfaces"  ''Trudy Geom. Sem. Inst. Nauchn. Inform. Akad. Nauk SSSR'' , '''3'''  (1971)  pp. 5–27  (In Russian)  (English summary)</TD></TR>
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