It requires good judgment to select topics for the moral and religious instruction of convicts, and much skill and tact to illustrate them. A false position on a moral subject will be quite as likely to strike a congregation of rogues as a congregation of honest men; and it is wonderful how the faith of a disciple is weakened by a single material error in a teacher. The moral instructor of prisoners, having nothing to do with points of polemic theology or subtle casuistry, has a plain and easy path if he is only willing to keep it. The elementary truths of religion and morality, which lie within the comprehension alike of a child and of an angel, and which are recognized by all sober-minded men as the basis and stamina of all true moral reformation, are to be explained and enforced, and their influence in promoting happiness, respectability and prosperity in this life and in preparing us for the future, is to be clearly exhibited. In illustrating these truths, much depends on a seasonable reference to those things within the knowledge or present consciousness of the convicts. Incidents of daily observation--the familiar phenomena of nature, their own history in its social and moral relations, (with which the teacher is supposed to have made himself acquainted) will furnish topics appropriate in character and abundant in variety. VI. _It is very important that a moral instructor should possess the faculty of casual teaching._--It is an easy thing to occupy ten or fifteen minutes in talking with a convict, but if he would leave something behind him for the man to ponder and reflect on when the cell-door closes again, the visitor or instructor must weigh well what he says, and seize the opportunity to drop a casual word of admonition, or encouragement, or intimidation, as the condition and habits of each individual may warrant. These casual suggestions often have far more weight than a studied sermon, or an elaborate and earnest exhortation. The methods of exerting an influence over others, and especially over thoughtless and perverse persons, would be much more appropriate and effective were they governed less by the teacher's own state of mind, and more by the state of the mind which he wishes to change. Moral instructors of all grades are oftentimes in the dark respecting the mental condition and habits of their catechumens; and prison chaplains or instructors not unfrequently err in occupying so much of their interviews in expostulation, reproof and entreaty, as to leave no proper opportunity to hear, much less to draw out, an expression of the convict's own feelings. In such a case their labors, however well meant, lose much of their value, and are sometimes worse than wasted.