Once there were but the spear and bow and shield, and hand-to-hand conflicts of brute strength. See now the whole enginery of war, the art of fortification, the terrific perfection of artillery, the mathematical transfer of all from the body to the mind, till the battlefield is but a chess-board, and the battle is really waged in the brains of the generals. How astonishing was that last European field of Solferino, ten miles in sweep,--with the balloon floating above it for its spy and scout,--with the thread-like wire trailing in the grass, and the lightning coursing back and forth, Napoleon's ubiquitous aide-de-camp,--with railway-trains, bringing reinforcements into the midst of the _melée_, and their steam-whistle shrieking amid the thunders of battle! And what a picture of even greater magnificence, in some respects, is before us to-day! A field not of ten, but ten thousand miles in sweep! McClellan, standing on the eminence of present scientific achievement, is able to overlook half the breadth of a continent, and the widely scattered detachments of a host of six hundred thousand men. The rail connects city with city; the wire hangs between camp and camp, and reaches from army to army. Steam is hurling his legions from one point to another; electricity brings him intelligence, and carries his orders; the aëronaut in the sky is his field-glass searching the horizon. It is practically but one great battle that is raging beneath him, on the Potomac, in the mountains of Virginia, down the valley of the Mississippi, in the interiors of Kentucky and Tennessee, along the seaboard, and on the Gulf coast. The combatants are hidden from each other, but under the chieftain's eye the dozen armies are only the squadrons of a single host, their battles only the separate conflicts of a single field, the movements of the whole campaign only the evolutions of a prolonged engagement. The spectacle is a good illustration of the day. Under the magic of progress, war in its essence and vitality is really diminishing, even while increasing in _materiel_ and grandeur. Neither time nor space will permit the old and tedious contests of history to be repeated. Military science has entered upon a new era, nearer than ever to the period when wars shall cease.