Aug., Sep., and Oct., 63.I AM in the habit of going to all, and to Fairfax seminary, Alexandria, and over Long bridge to the great Convalescent camp. The journals publish a regular directory of thema long list. As a specimen of almost any one of the larger of these hospitals, fancy to yourself a space of three to twenty acres of ground, on which are groupd ten or twelve very large wooden barracks, with, perhaps, a dozen or twenty, and sometimes more than that number, small buildings, capable altogether of accommodating from five hundred to a thousand or fifteen hundred persons. Sometimes these wooden barracks or wards, each of them perhaps from a hundred to a hundred and fifty feet long, are rangd in a straight row, evenly fronting the street; others are plannd so as to form an immense V; and others again are ranged around a hollow square. They make altogether a huge cluster, with the additional tents, extra wards for contagious diseases, guard-houses, sutlers stores, chaplains house; in the middle will probably be an edifice devoted to the offices of the surgeon in charge and the ward surgeons, principal attaches, clerks, &c. The wards are either letterd alphabetically, ward G, ward K, or else numerically, 1, 2, 3, &c. Each has its ward surgeon and corps of nurses. Of course, there is, in the aggregate, quite a muster of employés, and over all the surgeon in charge. Here in Washington, when these army hospitals are all filld, (as they have been already several times,) they contain a population more numerous in itself than the whole of the Washington of ten or fifteen years ago. Within sight of the capitol, as I write, are some thirty or forty such collections, at times holding from fifty to seventy thousand men. Looking from any eminence and studying the topography in my rambles, I use them as landmarks. Through the rich August verdure of the trees, see that white group of buildings off yonder in the outskirts; then another cluster half a mile to the left of the first; then another a mile to the right, and another a mile beyond, and still then another between us and the first. Indeed, we can hardly look in any direction but these clusters are dotting the landscape and environs. That little town, as you might suppose it, off there on the brow of a hill, is indeed a town, but of wounds, sickness, and death. It is Finley hospital, northeast of the city, on Kendall green, as it used to be calld. That other is Campbell hospital. Both are large establishments. I have known these two alone to have from two thousand to twenty-five hundred inmates. Then there is Carver hospital, larger still, a walld and military city regularly laid out, and guarded by squads of sentries. Again, off east, Lincoln hospital, a still larger one; and half a mile further Emory hospital. Still sweeping the eye around down the river toward Alexandria, we see, to the right, the locality where the Convalescent camp stands, with its five, eight, or sometimes ten thousand inmates. Even all these are but a portion. The Harewood, Mount Pleasant, Armory-square, Judiciary hospitals, are some of the rest, and all large collections.