Upon such a wooden shovel Abraham was able to work his sums by the flickering firelight. If he had no pencil, he could use charcoal, and probably did so. When it was covered with figures he would take a drawing-knife, shave it off clean, and begin again. Under these various disadvantages, and by the help of such troublesome expedients, Abraham Lincoln worked his way to so much of an education as placed him far ahead of his schoolmates, and quickly abreast of the acquirements of his various teachers. The field from which he could glean knowledge was very limited, though he diligently borrowed every book in the neighborhood. The list is a short one--"Robinson Crusoe," Aesop's "Fables," Bunyan's "Pilgrim's Progress," Weems's "Life of Washington," and a "History of the United States." When he had exhausted other books, he even resolutely attacked the Revised Statutes of Indiana, which Dave Turnham, the constable, had in daily use and permitted him to come to his house and read. It needs to be borne in mind that all this effort at self-education extended from first to last over a period of twelve or thirteen years, during which he was also performing hard manual labor, and proves a degree of steady, unflinching perseverance in a line of conduct that brings into strong relief a high aim and the consciousness of abundant intellectual power. He was not permitted to forget that he was on an uphill path, a stern struggle with adversity. The leisure hours which he was able to devote to his reading, his penmanship, and his arithmetic were by no means overabundant. Writing of his father's removal from Kentucky to Indiana, he says: "He settled in an unbroken forest, and the clearing away of surplus wood was the great task ahead. Abraham, though very young, was large of his age, and had an ax put into his hands at once; and from that till within his twenty-third year he was almost constantly handling that most useful instrument--less, of course, in plowing and harvesting seasons."