A mile of valley and undulating slopes separated Cemetery Hill from Seminary Ridge, and their crests were crowded with artillery when the sun rose on July 3, 1863. But for a time the battle was confined to the infantry, the Confederates continuing fierce assaults of the previous evening. Then, suddenly, all their troops were withdrawn, firing ceased and absolute silence ensued along their whole lines. At an utter loss to understand this complete disappearance of the foe, the Union commanders peered through their glasses at the silent and apparently deserted heights of Seminary Ridge, growing more and more nervous as time wore on. What was the explanation of this ominous silence? Was it possible that Lee had retreated? Was he trying to lure them out of their position and catch them in some giant ambuscade? Was he engaged in a flanking movement such as had crumpled them to pieces at Chancellorsville? Doubtless, more than one soldier shot an apprehensive glance toward the rear during the strange hush as he remembered the terrifying appearance of Jackson on that fearful day. But no Jackson stood at Lee's right hand, and suddenly two sharp reports rang out from the opposing height. Then, in answer to this signal, came the crash of a hundred and thirty cannon and instantly eighty Union guns responded to the challenge with a roar which shook the earth, while the air was filled with exploding shells and the ground was literally ploughed with shot. For an hour and a half this terrific duel continued; and then the Union chief of artillery, seeing that his supply of ammunition was sinking, ordered the guns to cease firing and the Confederates, believing that they had completely demolished the opposing batteries, soon followed their example. Another awful silence ensued and when the Union troops peered cautiously from behind the stone walls and slopes which had completely protected them from the wild storm of shot and shell, they saw a sight which filled them with admiration and awe.