This collection consists of a single diary with one-page entries for the year of 1862. A few pages of memoranda follow on which Barnett has listed miscellaneous clothing expenses and his pay record for the year. The diary describes his time in hospital in January and February, as well as from September through December. These latter entries include his work as a nurse, particularly tending to the wounded following the battle of Fredericksburg in December 1862. Camp life and routine, visits with his brother Henry, and brief trips into Washington D.C. are among the topics mentioned. Barnett also mentions review of the division by President Lincoln, General McDowell, and Secretary Stanton in May near Fredericksburg and again by Lincoln and McClellan in July near Harrison's Landing. The diary includes descriptions of battle at Mechanicsville, Gaines' Mill, Frazier's Farm, and Malvern Hill in the Seven Day's campaign and at the Second Battle of Bull Run.