Exhibit explores Gustavino family's structural-tile technique

In 1759, Samuel Johnson launched a letter-writing campaign against the design for a new Blackfriars bridge in London. The proposed span would have used elongated or elliptical arches, which infuriated the curmudgeonly and conservative Johnson, who preferred old-fashioned, semicircular arches, like the Romans built. Commerce depends on bridges, which should be built for strength, and the strongest arches -- as any intelligent person can deduce -- are semicircular, Johnson argued. Supporters of th...