How did the Schlesinger and Mayer department store emphasize horizontal lines?

In contrast to the vertical emphasis seen in his earlier office buildings, such as the Wainwright and Guaranty buildings, Louis Sullivan designed the Schlesinger & Mayer department store (now the Sullivan Center) to stress horizontal lines.12

This horizontal emphasis was achieved primarily through the use of rectangular "Chicago windows." These windows consist of a large fixed central pane flanked by movable sash windows, which help define the building's horizontal rhythm across its upper floors. Additionally, the building's design features a clear distinction between the upper levels and the lower floors; while the upper floors maintain an elegant simplicity, the first two levels are treated as display windows, with rich, naturalistic cast-iron ornament forming elaborate picture frames that further accentuate the structure's horizontal orientation.2