562 Of Chimney Fireplaces. 



ably be beat back into the room ; but when the breast 

 of the chimney is properly rounded off, the ascending 

 cloud of dust and smoke more easily finds its way into 

 the throat of the chimney, and is even directed and 

 assisted in some measure by the warm air of the room 

 that gets under the mantle, and is going the same way. 



Another very common fault that I have observed in 

 chimney fireplaces, that have been altered on what have 

 been called my principles, and which has a direct ten- 

 dency to bring dust, and even smoke, into the room, is 

 the sloping of the covings too much, and leaving the 

 opening of the fireplace in front too wide. I have said, 

 in my Essay on Chimney Fireplaces, that where chimneys 

 are well constructed and well situated, and have never 

 been apt to smoke, in altering them the covings may be 

 placed at an angle of 135 degrees with the back; but I 

 have expressly said that they should never exceed that 

 angle, and have stated at large the bad consequences 

 that must follow from making the opening of a fireplace 

 very wide, when its depth is very shallow (see page 

 510). I have also expressly said (page 530), that, 

 for chimneys that are apt to smoke, the covings should 

 be placed less obliquely^ in respect to the back, than in 

 others that have not that fault. But most of the work- 

 men who have altered chimneys seem to have paid little 

 attention to these distinctions, and I have frequently 

 found, and sometimes in fireplaces that have been re- 

 markably shallow, that the covings have been placed at 

 an angle even more oblique than that above mentioned. 



Another cause that sometimes has considerable effect 

 in bringing dust and smoke into rooms, from the fires 

 that are made in them, is the great nicety with which the 

 doors and windows are fitted in their frames, which pre- 



