... side of the surface, or some on the same side, and some on < ;the surface> itself, but none on the other side. /5/ And, when a cone cuts a sphere, having a vertex at the center of the sphere, ... taken, the straight <lines> between the <two> points either all fall on the same side of the line, or some fall on the same side, and some on the line itself, but none on the other ... consideration of the work. Once the groundwork is laid, in Propositions 1–22, the second half of the work is less constrained by strong deductive relations, one result leading to the next: the...