In many respects cavalry is the most difficult branch of military service to maintain and to operate. It is exceedingly costly, on account of the great loss of horses by the carelessness of the men, by overwork, by disease, and by the fatalities of battle. The report of General Halleck, for the year 1863, stated that from May to October there were from ten thousand to fourteen thousand cavalry in the Army of the Potomac, while the number of horses furnished them for the same period was thirty-five thousand; adding to these the horses taken by capture and used for mounting men, the number would be sufficient to give each man a horse every _two months_. There were two hundred and twenty-three regiments of cavalry in the service, which, at the same rate, would require four hundred and thirty-five thousand horses. This is an immense expenditure of animals, and is attributable in part to the peculiarities of the volunteer service--such as the lack of care and knowledge on the part of the officers, and the disposition of the men to break down their horses by improper riding, and sometimes out of mere wantonness, for the purpose of getting rid of animals they do not like, for the chance of obtaining better. A measure has recently been adopted to remedy these evils, by putting into the infantry cavalry officers and men who show themselves incompetent to take proper care of their animals, and who neglect other essentials of cavalry service. The provision and transportation of forage for cavalry horses also constitute items of great cost. To attain proficiency and effectiveness, cavalry soldiers require much longer instruction than those of any other arm. They must become expert swordsmen, and acquire such skill in equitation that horse and rider shall resemble the mythical centaurs of the ancients--shall be only one individual in will. The horses should be as thoroughly trained as the riders. In European armies this is accomplished in training schools. The Governments keep constantly on hand large supplies of animals, partly purchased and partly produced in public stables, and capable instructors are continually employed in fitting both men and horses for their duties. To insure the provision of proper horses and to recuperate those which are sent from the army disabled or sick, an immense cavalry depot has been established at Giesboro', near Washington. Thousands of horses are kept there ready for service, and as fast as men in the army are dismounted by the loss of their animals, they are sent to this depot. It is one of the most useful and best-arranged affairs connected with our service, and has greatly assisted in diminishing the expense attending the provision of animals, and in increasing the efficiency of our cavalry.