"For the same reason, that is... to prevent eddies, the breast of the Chimney, which forms [the front] side of the throat... or nearest to the room, should be neatly cleaned off, and its surface made quite regular and smooth. This may easily be done by covering it with a coat of plaister, which may be made thicker or thinner in different parts as may be necessary in order to bring the breast of the Chimney to be of the proper form."