5 1 6 Of Chimney Fireplaces. 



chimney, this manner of uniting the lower extremity of 

 the canal of the chimney with the throat would tend to 

 assist the winds which may attempt to blow down the 

 chimney, in forcing their way through the throat, and 

 throwing the smoke backward into the room ; but when 

 the throat of the chimney ends abruptly, and the ends 

 of the new walls form a flat horizontal surface, it will be 

 much more difficult for any wind from above to find 

 and force its way through the narrow passage of the 

 throat of the chimney. 



As the two walls which form the new covings of the 

 chimney are not parallel to each olher, but inclined, 

 presenting an oblique surface towards the front of the 

 chimney, and as they are built perfectly upright and 

 quite flat, from the hearth to the top of the throat, 

 where they end, it is evident that a horizontal section 

 of the throat will not be an oblong square ; but its 

 deviation from that form is a matter of no consequence ; 

 and no attempts should ever be made, by twisting the 

 covings above, where they approach the breast of the 

 chimney, to bring it to that form. All twists, bends, 

 prominences, excavations, and other irregularities of 

 form, in the covings of a chimney, never fail to pro- 

 duce eddies in the current of air which is continually 

 passing into and through an open fireplace in which a 

 fire is burning; and all such eddies disturb either the 

 fire, or the ascending current of smoke, or both, and 

 not unfrequently cause the smoke to be thrown back 

 into the room. Hence it appears, that the covings of 

 chimneys should never be made circular, or in the form 

 of any other curve, but always quite flat. 



For the same reason, that is to say, to prevent eddies, 

 the breast of the chimney, which forms that side of the 



