Erard… begins by visiting Bologna, Italy, the hometown of one of history’s most distinguished polyglots, the 19th-century cardinal Giu­seppe Mezzofanti. The cardinal is said to have known 45, 50, 58 or even more languages, depending on whom you ask. Victorian travelers who met him at ecclesiastical banquets reported that he affably conversed in all directions with foreign visitors in languages ranging from French, German and Arabic to Algonquin and “Californian.” (Lord Byron, who challenged the cardinal to a multilingual contest of profanities, was not only summarily defeated but walked away from the contest having learned a number of new Cockney gibes.) No less a figure than Pope Gregory XVI, in an attempt to catch Mezzofanti out, orchestrated a prank in which he secretly gathered dozens of foreign seminarians and then unleashed them on the unsuspecting cleric, all of them addressing him loudly in a tangle of languages. With much aplomb, Mezzo­fanti took up the pontiff’s challenge, answered them, and prevailed.