As soon as the grand assualt was replused, Meade went to the extreme left of his line with the determination of advancing the left, and making an assualt upon the enemy...At five o'clock, Crawford recieved orders from Sykes to advance McCandless's brigade, then just east of the Wheat Field, to enter the woods, and drive out the enemy. Sedgewick sent two brigades to cooperate. At about 5.30, McCandless, followed by Nevin, with Bartlett in reserve, dashed across the Wheat Field, cleared the woods in front, and then turned to the left, charged Benning's brigade on the left flank, and captured many prisoners. Longstreet's right fell back to Seminary Ridge. "The great length of the line," says Meade, "and the time required to carry these orders out to the front, and the movement subsequently made, before the report given to me of the condition of the forces in the front and left, caused it to be so late in the evening as to induce me to abandon the assualt which I had contemplated."
The next day,...it was reported to Meade from the extreme right that the enemy had disappeared; but that they still maintained their appearance on his left and center. Slocum's corps advanced; and Howard's pushed into Gettyburg, and found that the enemy had retired from his circular position and assumed one nearly parallel to Meade's left and center. It rained very violently during portions of this day, "so violently," says Meade, "as to interrupt any very active operations if I had designed making them."
During the night he learned that the enemy had retired through the Fairfield and Cashtown passes.
"The Story of the Civil War", Vol. II, Livermore, 1913.
The Meade's Army had been marching for many days and miles to find Lee and then fought a terrific three day battle in exhausting terrain and July weather. They were simply too spent to pursue.