Allied to the matter just mentioned was Plucker's discovery of the six equations connecting the numbers of singularities in algebraical curves (see Curve).
From this time Plucker's geometrical researches practically ceased, only to be resumed towards the end of his life.
Xvi.), to which is appended an appreciation of Plucker's physical researches by Hittorf, and a list of Pliicker's works by F.
Gerhardt, Geschichte der Mathematik in Deutschland, p. 282, and Plucker's life by A.
The whole theory of the inflections of a cubic curve is discussed in a very interesting manner by means of the canonical form of the equation x +y +z +6lxyz= o; and in particular a proof is given of Plucker's theorem that the nine points of inflection of a cubic curve lie by threes in twelve lines.