What are some examples of formal diction?

Certainly Irving used formal diction for the time. Consider this quote,

"Any one but he would have felt unwilling to linger in this lonely, melancholy place, for the common people had a bad opinion of it, from the stories handed down from the times of the Indian wars, when it was asserted that the savages held incantations here and made sacrifices to the Evil Spirit."

Note words like "savages" , "meloncholy" , and "incantations" would have been considered formal at the time.