A letter of introduction should not, unless circumstances make it absolutely unavoidable, be delivered in person. It should be sent, with the card of the person introduced, to the person to whom it is addressed, by a servant. The person receiving it should then call at once or send a written invitation to his house, and the person introduced may then call in person. If, however, the stay in the city is very short, these formalities must be omitted, and the person introduced call in person, sending in his letter and card by a servant. Business letters of introduction should mention the errand and business of the party introduced, and if your own acquaintance is of recent date, mention by whom your were yourself introduced. Letters introducing professional artists may contain a few words expressive of the pleasure conferred by the talent or skill of the person introduced. Letters of introduction soliciting favors should be but seldom given, and never unless the claims upon both parties interested are very strong. There is no rule of etiquette prescribing the exact amount of attention required to be shown to the bearer of a letter of introduction by the person to whom it is addressed. A thousand circumstances of time, place, position, leisure and disposition of the parties must control this, but as a rule, the most generous hospitality and courtesy it is possible to give, should be extended to your friend's friend. It is a compliment to both the bearer and the writer of the letter. La Fontaine says: "A letter of introduction is a draft at sight, and you must cash it." It might be added, "You must cash it in full, never allowing the courtesy exchange to be against the presenter of the draft." Letters of introduction should bear upon the envelope the name and address of the party introduced, written in the left hand corner-- thus: JOHN JONES, ESQ., No. 714 --- Street, Philadelphia. Introducing L. F. Townsend, Esq., of Troy. Letters of introduction to and from business men, for business purposes, may be delivered by the bearers in person, and etiquette does not require the receiver to entertain the person introduced as the private friend of the writer. Good nature and native courtesy would suggest some attentions, which could be increased according to the pleasure conferred or received, but it is entirely optional. Letters of introduction are very useful to travellers, or those about to change their place of residence; care, however, should be especially taken in the latter case to present persons to each other only, who will prove mutually agreeable, as it is surely no friendly act to force upon your friends a life-long acquaintance, perhaps with uncongenial persons.