A "coach" is a large enclosed four-wheeled carriage, drawn by four or more horses, with at least two rows of seats in the compartment, and usually with seats on the top etc. The "box" is a luggage compartment to the front of the main coach body; the driver either sits on this coach box, or sits on the front edge of the coach body with his legs resting on the box (depending on the design of the coach); there is also usally a "basket", or open luggage compartment hanging from the rear of the coach body.
Coaches are used by wealthy families, and in long-distance public transportation. ) and six, with a "box" in front and "basket" behind (Rowlandson, 1798).
To save postage, letters were frequently "crossed": i.e.
after a sheet of paper had been written on, it was turned 90°, and further lines were written crossing the original writing (there is a reference to this practice in ).
So Elinor Dashwood in Jane Austen's novel , when she sees a letter from Edward Ferrars to Lucy Steele, thinks "a correspondence between them by letter could subsist only under a positive engagement, could be authorised by nothing else", and, when she is unsure whether or not Willoughby and Marianne are engaged, says "If we find they correspond, every fear of mine will be removed".