Be that as it may, the order was given for his artillery to open. Longstreet had massed seventy-five guns in one battery, Hill sixty-three, and Ewell enough more to bring the number up to one hundred and fifty in all. At precisely one o'clock the signal guns were fired. Before their echoes died away the whole line of Confederate batteries was blazing like a volcano. There seemed to be but one flash and one report, and their simultaneous discharges, pealing out deafening salvos, went rolling and rolling on through the valleys, and echoing among the hills, in one mighty volume of sound, vying with the loudest thunder. It was sublimely grand, sublimely terrifying. Without a moment's warning, as if the heavens above had opened and the earth below yawned beneath their feet, the Union soldiers found themselves in the midst of the pitiless storm. A tornado of shot and shell burst upon Cemetery Hill, tearing the air, rending the rocks, plowing up the ground, and dealing death on all sides at once. This terrific cannonade, under which the solid earth shook, the sky was darkened at noonday, the valley filled with thick-rolling smoke, the air with explosions and nameless rubbish, and which seemed announcing the coming of the Last Day, is thus described by an eye-witness:-- "The storm broke upon us so suddenly that soldiers and officers who leaped, as it began, from their tents, or from lazy siestas on the grass, were stricken at their rising with mortal wounds, and died, some with cigars between their lips, some with pieces of food in their fingers, and one at least--a pale young German from Pennsylvania--with a miniature of his sister in his hands. Horses fell shrieking out such awful cries as Cooper told of, and writhing themselves about in hopeless agony. The boards of fences, scattered by explosions, flew in splinters through the air. The earth, torn up in clouds, blinded the eyes of hurrying men; and through the branches of the trees and among the gravestones of the cemetery a shower of destruction crashed ceaselessly. The hill, which seemed alone devoted to this rain of death, was clear in nearly all its unsheltered places within five minutes after the fire began." Eighty guns replied from the Union position almost as soon, so that the very air between the two armies was alive with flying missiles.[73] During the cannonade the Union infantry were lying down in open ranks behind the crest, taking it, for the most part, with remarkable steadiness. As the enemy's artillerists mostly overshot the ridge, the ground behind was a place of even greater danger. The little farmhouse standing on the Taneytown road, occupied as army headquarters, was so riddled that the general was compelled to seek a safer spot. Even as far back as Culp's Hill, where the Twelfth Corps were still facing their assailants, the enemy's shot came plunging and plowing through the ranks from behind, thus killing men by a fire in the rear.