Punctuation marks help to clarify the meaning of a sentence. Here is a sentence where the punctuation needs improvement.
“The sitting room was bright and cheery; small, but warm, and with the fire that crackled in the marble hearth it was rather cozy.”
Since the phrase small, but warm describes the sitting room, it should not be set off by a semicolon. To correct the sentence, change the semicolon to a comma, remove the comma before but, and use a semicolon before and.
The sitting room was bright and cheery, small but warm; and with the fire that crackled in the marble hearth it was rather cozy.