Thomas U. Walter’s draftsman drew a plan of the structural elements of the Capitol’s tholus, or dome. He created a trompe l’oeil (fool-the-eye) effect of a smaller drawing of the cross section laying on top of another drawing sheet showing the same element in elevation. The construction drawings were skillfully done in ink and filled in with watercolor. The details needed to be clear and exact, as they were used to guide the casting of the iron structural pieces in New York.
Architect of the Capitol