An unpublished diary which Ruskin kept during the summer of 1842 when he was conceiving the plan of Modern Pointers furnishes new information on the development of his mind at that time. Writing of this year in Praeterita, Raskin was obliged to rely on a memory weakened by age and disease. “To my sorrow, and supreme surprise,” he noted in his autobiography which he had begun in 1885, “I find no diary whatever of the feelings or discoveries of this year.” He apparently had forgotten that in 1872 he had given such a diary as a Christmas present to his American friend, Charles Eliot Norton. This important manuscript, which remained in the Norton family until 1936 and was then donated to the Yale University Library as a gift of Mr. and Mrs. Arnold Whitredge, seems to have been unknown to Ruskin's editors and succeeding students of his ideas. As reliable and recent a work as Derrick Leon's biography of Ruskin makes no mention of it and follows instead the account of the events of 1842 offered in Praeterita. A comparison of the manuscript with Praeterita shows that Ruskin's memory had dramatized this year of his youth in a way that misrepresented the state of mind in which Modern Painters was begun.