"If it should be necessary to diminish the opening of a large Chimney in order to prevent its smoking, it is much more simple, œconomical, and better in all respects, to do this with marble, fire-stone, or even with bricks and mortar, than to make use of iron, which... is the very worst material... for that purpose; and as to registers, they not only are... unnecessary, where the throat of a Chimney is properly constructed, and of proper dimensions, but in that case would do mach harm. If they act It all, it must be by opposing their flat surfaces to the current of rising smoke in a manner which cannot fail to embarrass and impede its motion. But... the passage of the smoke through the throat of a Chimney ought to be facilitated as much as possible in order that it may be enabled to pass by a small aperture."