When the width of the opening of the Fire-place, in front, is very great, compared with the depth of the Fire-place, and with the width of the back, the covings in that case being very wide, and consequently very oblique, and the Fire-place very shallow, any sudden motion of the air in front of the Fire-place, (that motion, for instance, which would be occasioned by the clothes of a woman passing hastily before the fire, and very near it,) would be apt to cause eddies in the air, WITHIN THE OPENING OF THE FIRE-PLACE, by which puffs of smoke might easily be brought into the room. Should the opening of the Chimney be too narrow, which however will very seldom be found to be the case, it will, in general, be advisable to let it remain as it is, and to accommodate the covings to it, rather to attempt to increase its width, which would be attended with a good deal of trouble, and probably a considerable expence. From all that has been said it is evident, that the points of the greatest importance, and which ought most particularly to be attended to, in altering Fire-places upon the principles here recommended, are, the bringing forward the back to its proper place, and making it of a proper width.--But it is time that I should mention another matter upon which it is probable that my reader is already impatient to receive information.--Provision must be made for the passage of the Chimney-sweeper up the Chimney.--This may easily be done in the following manner:-- In building up the new back of the Fire-place; when this wall, (which need never be more than the width of a single brick in thickness,) is brought up so high that there remains no more than about ten or eleven inches between what is then the top of it, and the inside of the mantle, or lower extremity of the breast of the Chimney, an opening, or door-way, eleven or twelve inches wide, must be begun in the middle of the back, and continued quite to the top of it, which, according to the height to which it will commonly be necessary to carry up the back, will make the opening about twelve or fourteen inches high; which will be quite sufficient to allow the Chimney-sweeper to pass. When the Fire-place is finished, this door-way is to be closed by a few bricks, by a tile, or a fit piece of stone, placed in it, dry, or without mortar, and confined in its place by means of a rabbet made for that purpose in the brick-work.--As often as the Chimney is swept, the Chimney-sweeper takes down this temporary wall, which is very easily done, and when he has finished his work, he puts it again into its place.--The annexed drawing (No. 6.) will give a clear idea of this contrivance; and the experience I have had of it has proved that it answers perfectly well the purpose for which it is designed.