Plate glass was first produced by the French, in the late seventeenth century, although the Romans had pioneered a primitive version in ancient times. By the 1840s plate glass sheets two feet (70 cm.) long were becoming available, but many of the buildings on this walk retain the Georgian style twelve-paned rectangular windows, which let in plenty of light without the need for expensive large plate glass sheets. Partially glazed French doors with louvred shutters were also popular in this period.