Andy Goldsworthy, artist. Two weeks after finishing his site-specific installation, Roof, on the Ground Level of the East Building of the National Gallery of Art, British artist Andy Goldsworthy returned to the Gallery to present the Elson Lecture on March 17, 2005. His lecture describes the working process involved for his concurrent exhibitions The Andy Goldsworthy Project and Andy Goldsworthy: Roof, which first showed the permanent sculpture of nine stacked slate domes, completed over the course of nine weeks in the winter of 2004-2005. Goldsworthy notes that the installation required him to stay in one place longer than he had in nearly 20 years. As an artist who uses natural materials to create both ephemeral work in landscapes and permanent sculptures, Goldsworthy explains his interest in change and the value of returning to the same place to get deeper and deeper into it.