"a very beautiful girl, in a big cartwheel hat, sitting in a victoria"
A Victoria Carriage
GNU Free Documentation LicenseA Victoria Carriage - Credit: A. McMurray/Wikimedia Commons

A cartwheel hat is a hat with a very large, flat, circular brim. Click here for images of these hats.

 

A victoria was a light, four-wheeled horse-drawn carriage with a folding hood.