one o’clock
Since the morning scarce a gunshot has been heard . Now and then only , a single cannon , like a signal-gun , sends its growl through the hills . Those two tigers , the army of Northern Virginia and the army of the Potomac , are crouching , and about to spring . At one o'clock the moment seems to have arrived . Along the whole front of Hill and Longstreet , the Southern artillery all at once bursts forth . One hundred and forty-five cannon send their threatening thunder across the peaceful valley . From Cemetery Heights eighty pieces reply to them ; and for more than an hour these two hundred and twenty-five cannon tear the air with their harsh roar , hurled back in crash after crash from the rocky ramparts .