Let us take, for example, the side of France bordering on the Rhine.

Wissembourg and Lauterbourg, Fort Louis, Haguenau, Strasbourg, Schelstadt, Neuf-Brisach, and Huneguen, cover the several passages of the river; while Bitche, Phalsbourg, and Befort form a second line; Thionville, Metz, and Toul, a third line; and Verdun a grand central depot.
The following are the principal objects proposed to be accomplished by fortifications on a sea-coast.
1st.

To close all important harbors to an enemy, and secure them to the navy of the country.
2d.

To prevent the enemy from forming an establishment on our shores, from which, by his naval superiority, he might destroy our commerce and keep the whole frontier in continual alarm.
3d.

To cover our great cities against a maritime attack and bombardment.
4th.