The facade of the I.M. Pei-designed National Gallery East Wing is now crumbling. Catesby Leigh reports in the Wall Street Journal that the building, constructed using an experimental curtain wall system that the architect described as "a technological breakthrough for the construction of masonry walls," has become unstable. The clean lines and solid geometrical forms of the building's design simply could not be interrupted with unsightly expansion joints. I.M. Pei quite simply was shackled to his own modern design, constrained to have large uninterrupted geometries of stone, a technological solution was an absolute necessity. The earlier Main Building, designed by...