[Footnote 25:  For further information concerning our system of sea-coast defences, the reader is referred to House Doc. 206, twenty-sixth Congress, second session; Senate Doc. 85, twenty-eighth Congress, second session; and to the annual reports of the Chief Engineer.]

CHAPTER VIII.

OUR NORTHERN FRONTIER DEFENCES.

In discussing engineering as a branch of the military art, we spoke of the use of fortifications on land frontiers, and their influence on the strategic operations of a campaign.  A brief notice was also given of the different systems that have been proposed for arranging these defensive works.  Let us now apply this discussion to our northern frontier.

The principle laid down by Napoleon and Jomini, “that fortifications should always be constructed on important strategic points,” is undoubtedly the correct one:  but how to determine these points is a question that will often perplex the patience and try the skill of the engineer; yet determine them he must, or his fortifications will be worse than useless; for a fort improperly located, like a cannon with its fire reversed on its own artillerists, will be sure to effect the destruction of the very forces it was designed to protect.

The selection of positions for fortifications on our northern frontier must have reference to three distinct classes of objects, viz.:  the security, first, of the large frontier towns, where much public and private property is exposed to sudden dashing expeditions of the foe, made either on land or by water; second, of lake harbors, important as places of refuge and security to our own ships, or to the enemy’s fleets while engaged in landing troops or furnishing supplies to an invading army; third, of all strategic points on the probable lines of offensive or defensive operations.  These objects are distinct in their nature, and would seem to require separate and distinct means for their accomplishment; nevertheless, it will generally be found that positions selected with reference to one of these objects equally fulfil the others, so intimately are they all connected.  To determine the strategic points of a probable line of military operations is therefore the main thing to be attended to in locating fortifications.  That such points of maximum importance are actually marked out by the peaceful or hostile intercourse of nations cannot be doubted.

The relative importance of cities and towns is less varied by the fluctuations of commerce on a land frontier than on the sea-coast.  The ever-changing system of “internal improvements,” by furnishing new highways and thoroughfares for the transportation of the products of manufacturers and agriculture, either continually varies the relative standing of the seaports already opened, or opens new ones for the exportation of these products, and the importation of foreign articles received in exchange.  But