At the commencement of the war the rebel cavalry was superior to that furnished by the North. For this there were many reasons. Southern plantation life had accustomed the aristocratic youth to the saddle, and great attention was bestowed on the training of horses. At the North the number of skilled riders was comparatively few. Gradually, however, Northern energy, endurance, and patient discipline began to tell, and the time soon arrived when the Southern cavalry were invariably driven, especially in sabre charges, to which Southerners have great aversion. At present, on account of the scarcity of horses, the difficulty of supplying forage, and the loss of so many gay youths of the chivalry, the Southern, cavalry has dwindled into such a condition as to be no longer formidable. The service of the cavalry in both armies during the war has been exclusively as light cavalry--scouting, picketing, raiding, etc. Its combats have been with forces of its own arm. No commander has yet succeeded in assisting to determine the issue of a pitched battle by the charges of his mounted troops. Our cavalry have rendered, however, brilliant and invaluable services in protecting the rear and flanks of the armies, and by their magnificent raiding expeditions into the enemy's country, destroying his supplies, injuring his communications, diverting his forces, and liberating his slaves. No sufficient accounts of such expeditions and of the numerous cavalry conflicts have been published; yet they are very desirable. They would furnish most interesting narratives, and be a valuable contribution not only to the history of the times, but to the history of warfare; for the operations of the cavalry in this war constitute a new era in the history of this branch of military service. Unless care is exercised to procure such narratives, our posterity will never know anything of many battle fields where fought and fell brave troopers from every Northern State. The chief duties of officers belonging to the _corps of engineers_, when connected with an army acting in the field, are the supervision of routes of communication, the laying of bridges, the selection of positions for fortifications, and the indication of the proper character of works to be constructed. Should a siege occur, a new and very important class of duties devolves on them, relating to the trenches, saps, batteries, etc.