Routledge's Manual of Etiquette, etiquette for ladies and gentlemen, ball-room companion, courtship and matrimony, how to dress well, how to carve, toasts and sentiments

"To introduce persons who are mutually unknown is to undertake a serious responsibility, and to certify to each the respectability of the other. Never undertake this responsibility without in the first place asking yourself whether the persons are likely to be agreeable to each other; nor, in the second place, without ascertaining whether it will be acceptable to both parties to become acquainted..."