The military hospitals, convalescent camps, etc., in Washington and its neighborhood, sometimes contain over fifty thousand sick and wounded men. Every form of wound (the mere sight of some of them having been known to make a tolerably hardy visitor faint away), every kind of malady, like a long procession, with typhoid fever and diarrhoea at the head as leaders, are here in steady motion. The soldier's hospital! how many sleepless nights, how many women's tears, how many long and waking hours and days of suspense, from every one of the Middle, Eastern, and Western States, have concentrated here! Our own New York, in the form of hundreds and thousands of her young men, may consider herself here--Pennsylvania, Ohio, Indiana, and all the West and Northwest the same--and all the New England States the same. Upon a few of these hospitals I have been almost daily calling as a missionary, on my own account, for the sustenance and consolation of some of the most needy cases of sick and dying men, for the last two months. One has much to learn to do good in these places. Great tact is required. These are not like other hospitals. By far the greatest proportion (I should say five sixths) of the patients are American young men, intelligent, of independent spirit, tender feelings, used to a hardy and healthy life; largely the farmers are represented by their sons--largely the mechanics and workingmen of the cities. Then they are soldiers. All these points must be borne in mind. People through our Northern cities have little or no idea of the great and prominent feature which these military hospitals and convalescent camps make in and around Washington. There are not merely two or three or a dozen, but some fifty of them, of different degrees of capacity. Some have a thousand and more patients. The newspapers here find it necessary to print every day a directory of the hospitals--a long list, something like what a directory of the churches would be in New York, Philadelphia, or Boston.