3. On the elements of lines. Relation that should exist between the crest and the internal size of a closed work. Maximum and minimum of the sides of a square redoubt. Defects inherent to the trace of this kind of redoubt. Circular redoubts. Redoubts _en crémaillères_. Star forts. Lines with bastions. 4. Revetments of various kinds; case in which the slope of the ditch should be reveted; choice to be made of the different kinds of revetments. 5. Exterior dispositions; accessories to the defense; abattis; _trous de loups_; palisades; _chevaux de frise_, &c. Precautions to be adopted with reference to such accessories. 6. Interior dispositions; armament of musketry, artillery, barbettes, and embrasures; their advantages and disadvantages; construction of. 7. Powder magazines of different kinds. Small earthen entrenchments; palisades, carpentry, or blockhouses; advantages and disadvantages of blockhouses. African blockhouse. Closing of field-works. 8. Artificial inundations; under what circumstances they can be considered as obstacles. Positions and dimensions of dikes. Details of their execution; what advantage can be drawn from an inundation having less than five feet depth of water. 9. What is understood by the defilading of a work. The defilading of fieldworks should, above all things, be made to depend on their trace and situation. Definitions: dangerous ground; dangerous points. Defilement of an isolated and closed work; in what case it is practicable. Use of traverses. A partial defilement may sometimes be sufficient. 10. Continuous lines. Broken lines. Traces of redan, tenailles, cromailleres. Bastioned lines. Comparison between continuous and broken lines. Principal objections to their use. Utility of each demonstrated under certain circumstances. 11. Lines in broken ground: their form should depend on the nature of the ground. On the manner of fortifying a table-land. Expedients for defilading portions of lines. On the manner of making use of the natural obstacles of the ground; forests, scarps, marshes, water-courses, &c. Method of fortifying a house, village, an open town. Defense of a bridge or road. 12. _Têtes de pont_. Utility of small earthen entrenchments in these cases to facilitate the passage of a retreating army. Traces of a large _tête de pont_. Principal circumstances relating to the use of lines in war. Lines of circumvallation and countervallation. Frontier lines. Retrenchments against a descent. Lines that an army should make in an enemy’s country, far from its base of operations. Entrenchment on the field of battle. Lines, mixed, proposed by General Rogniat. 13. Attack and defense of entrenchments, of a continuous line; of a line at intervals; of an isolated work, &c. Examples of the attack and defense of lines. 14. Instruction relating to the operations for profiling and defilading on the ground.