The life of William Cowper has been written many times; first by his friend and fellow poet, William Hayley, and most recently by Thomas Wright, Principal of the Cowper School at Olney. The present manuscript, here reprinted in full, was probably prepared for the first of these biographers about two years after the poet's death. It is in the hand of the Rev. John Johnson, Cowper's cousin and constant companion during the last five years of his life. It was doubtless used by Hayley for his brief record of these years, but seems to have been unknown to all succeeding biographers. The dismal circumstances of this part of Cowper's life combined with the unscientific historical attitude of a century ago to make Hayley's account altogether unsatisfactory today. The diary comes to the modern student of Cowper, therefore, as virtually new source material for those years of his life which have always been the least documented.