Page 58
Hence will follow▪ That if the centers of two like Ellipses be laid upon one line, as upon one of their common Diameters, and from any point assigned (unto which they are to be alike situated) there be an infinite line drawn to any point of one of the Ellipses, and the like point of the other Ellipsis be brought to that ••••finite line (the center of it still keeping upon the common Diameter,) those Ellipses in that situation shall stand alike posited to the assigned point.
Because there are two lines (the common diameter and the infinite line) that from the point assigned do cut like parts of both Ellipses. The common diameter makes them alike situate in respect of one dimension (suppose the length) of the locus planus whereon they lie, and the infinite line limits them in respect of the other dimension (suppose the breadth) of the same locus planus. So that they are quite limited in respect of their like situation to the point, and can (in this respect) lie in no other place for this individuall position.