[71.] Problem VII. 55. To find the Perſpective of a Line, perpendicular to the Geometrical Plane.

[72.] Operation.

[73.] Demonstration.

[74.] Method II.

[75.] Demonstration.

[76.] Method III.

[77.] Operation, Without Compaſſes.

[78.] Demonstration.

[79.] Scholium.

[80.] Corollary.

[81.] Problem VIII.

[82.] To do this another Way.

[83.] Demonstration.

[84.] Problem IX.

[85.] Problem X.

[86.] Demonstration.

[87.] EG: EN:: GY: NM.

[88.] Definition.

[89.] Problem XI.

[90.] Lemma.

[91.] Demonstration.

[92.] Remarks.

[93.] Problem IX.

[94.] Operation.

[95.] Demonstration.

[96.] Problem X.

[97.] Operation.

[98.] Demonstration.

[99.] Remarks.

[100.] Method II. 70. By the accidental Point of inclin’d Lines.