Snugly packed on the first floor's northeast corner in the New York Public Library's grand halls is the IRMA AND PAUL MILSTEIN DIVISION OF U.S. HISTORY, LOCAL HISTORY AND GENEALOGYa haven for fine, aged, bookish beauties. Among the two-tiered stacks' Works Progress Administration records, World War accounts, and census records you might be so lucky to find an elder to teach you a thing or two. The infrequent visitor, researching family background, is your best bet. Guide her through the Ancestry.com database and let her tell you how she moved to Washington Heights at the turn of the century with her adopted parents, and how her Philadelphia-born mother got pregnant at 19, then gave her up. How she worked as a substitute 10th grade teacher nearly her whole life. If you're open, she'll slip a tale and tongue gently across the slope of your youthful neck.