seven o'clock
He immediately ordered his attack on the centre and left of his enemy . The artillery horses were cropping the tender dew-laden grass with eagerness . They had had no breakfast . The riders sprang to their backs at seven o'clock and they dashed into position . Lee 's guns opened the fateful day . For hours his lines blazed with the steady sullen boom of artillery and rattle of musketry . Hooker 's hosts replied in kind .