The Penitentiary, which is under the wardenship of Mr. Fitch, is capable of accommodating about seven hundred and fifty prisoners, but at present their numbers are slightly under five hundred--about three hundred men, and ninety women. The prisoners are divided into classes, the particular dress of each indicating the nature and gravity of their offences, and though amenable to the same laws as to labor and discipline, they work in separate gangs and mess by themselves. They are under the control of twenty-four keepers, each keeper, who is heavily armed, having fifteen men in his charge, whose roll he calls, and for whose absence he is responsible. At six o'clock the prisoners are all paraded to call the roll, at half-past six they have breakfast, consisting of dry bread and a bowl of coffee, and at seven, those who are skilled workmen are told off to the blacksmiths', carpenters', tailors', and weavers' shops, where all necessary repairs to the building and its fittings are done, and the clothing for the prisoners is made; others to labor in the gardens and fields, while the remainder are marched off in two divisions, one to work in the stone quarries at home, the others to be conveyed by the Commissioners' steam vessel Bellevue to the quarries on Ward's Island. The female prisoners are principally occupied in the sewing-room, in the brush-manufactory, in washing clothes, and scrubbing out the cells. The majority of the prisoners are committed for assault and battery or larceny, for terms varying from one month to four years and a half; those committed for graver offences are confined at Sing Sing; all drunkards, vagrants, and disorderly characters at the workhouse. During the past year two thousand three hundred and fifteen persons were incarcerated for different periods--two thousand one hundred and thirty-nine whites, one hundred and seventy-six blacks. Of these about one third were native Americans, one third Irish, one tenth German, and the remainder of various nationalities. The visitor to the Penitentiary cannot but be struck by the youth of the male prisoners compared with that of the females, the bulk of the males being between fourteen and thirty years of age, the females between twenty-five and fifty. Few young girls find their way here, as in their earlier career they are able to gain enough by a life of prostitution, without committing larceny, and consequently do not resort to it till their charms begin to wear, and the consequent diminution of their means of subsistence from such a source compels them to resort to some other. There is another fact which appears in these statistics of crime, one highly suggestive to the housekeeper. Of the four hundred and eleven female prisoners committed during the past year, no less than three hundred and two were domestic servants, and of these two hundred and forty-one were Irish girls and women.