"I hope you saw her petticoat, six inches deep in mud, I am absolutely certain; and the gown which had been let down to hide it"
Fashionable evening dresses - 1818
Public DomainFashionable evening dresses - 1818

The gown was a woman's skirted overgarment, worn over one or more petticoats.

The petticoat was an undergarment, often finished in lace. It was typically made to be seen, with the gown cut shorter than the petticoat.