"When the throat of a chimney is situated very high up above the mantle, and especially when the mantle and breast of the chimney, or the wall that reposes on the mantle, are very thin, workmen who are employed to alter chimnies, setting about the work with their minds strongly prepossessed with what they consider as the leading principle... that the throat of the chimney should not be more than four inches wide, they are very apt to bring the grate too far forward. In dropping their plumb-line from the breast of the chimney, they do not reach up high enough into the chimney, but take a part of the breast, where it still goes on to slope backwards, for the bottom of the perpendicular canal of the chimney. They also very often commit another fault, not less essential... in neglecting to bring down the throat of the chimney nearer to the fire, when... too high."