It s a detail, but the details accumulate, Tufte explains. It s design by aggregate pickiness. On Courbet, alternate grids are tried out. On Mondrian, Tufte watches as the storm unfolds over and over again, growing from a bead of mercury into something like a slug, then an anvil, then a delirious version of Dumbo the elephant. The storm slides above the grid, slips in front of the tripod scale.
Tufte is delighted.
You know right away it s supporting information, not primary. Flying home that evening, his plane passes over Chicago. It is a breathtakingly clear night, at rush hour. The grid of the city glows. Lending scale are the Hancock and Sears towers, shifting in relationship to each other on the horizon, alternately concealing and revealing each other as the plane banks.