In Bierma's recent language column, he talks about Hartley's ""Lewis and Clark Lexicon of Discovery," which aims to explain interesting words of the 19th century, as well as to give the readers a feel for English during that time.

It especially helped that Clark spelled phonetically, rather than correctly. We can see how they pronounced words during that time. For example, Clark spells "board" as "boad" and "horse" as "hose," while Lewis spells "sharp" as "shap" and "shortly" as "shotly." These phonetic spellings suggest the men pronounced the words without an "r" -- a phonetic feature of the accent of Virginia, where both men were born. Hartley describes some of the dialects of the time as: Virginia drawl, Ohio River backcountry lingo, New Hampshire twang, lilting French Canadian and American Indian.

It is interesting that the misspellings have been so useful to the linguists.