midnight
He kept a straight course for the Potomac , at least half of his men knowing thoroughly every foot of the way . `` What time can we reach the river and the place at which they say McClellan is going to cross ? '' asked Harry . `` By midnight anyway , '' replied Sherburne . `` Of course , we 'll have to slow down as we draw near , or we may run square into an ambush . Do you see that grove about two miles ahead ? We 'll go into that first , rest our horses , and take some food . ''