"Various have been the contrivances to avoid this: such as bringing in fresh air through pipes, in the jams of the chimney, which, pointing upwards, should blow the smoke up the funnel; opening passages into the funnel above, to let in air for the same purpose. But these produce an effect contrary to that intended; for, as it is the constant current of air passing from the room through the opening of the chimney into the funnel, which prevents the smoke coming out into the room, if you supply the funnel by other means, or in other ways, with the air it wants, and especially if that air be cold, you diminish the force of that current, and the smoke, in its efforts to enter the room, finds less resistance."