496 Of Chimney Fireplaces. 



practice, building a wall of bricks, supported by a flat 

 bar of iron, immediately under the mantle. 



Nothing is so effectual to prevent chimneys from 

 smoking as diminishing the opening of the fireplace in 

 the manner here described, and lowering and diminishing 

 the throat of the chimney; and I have always found, 

 except in the single instance already mentioned, that a 

 perfect cure may be effected by these means alone, even in 

 the most desperate cases. It is true, that when the con- 

 struction of the chimney is very bad indeed, or its situ- 

 ation very unfavourable to the ascent of the smoke, and 

 especially when both these disadvantages exist at the 

 same time, it may sometimes be necessary to diminish 

 the opening of the fireplace, and particularly to lower it, 

 and also to lower the throat of the chimney, more than 

 might be wished ; but still I think this can produce no 

 inconveniences to be compared with that greatest of all 

 plagues, a smoking chimney. 



The position of the throat of a chimney being de- 

 termined, the next points to be ascertained are its size 

 and form, and the manner in which it ought to be con- 

 nected with the fireplace below, and with the open canal 

 of the chimney above. 



But as the.se investigations are intimately connected 

 with those which relate to the form proper to be given to 

 the fireplace itself, we must consider them all together. 



That these inquiries may be pursued with due method, 

 and that the conclusions drawn from them may be clear 

 and satisfactory, it will be necessary to consider, first, 

 what the objects are which ought principally to be had 

 in view in the construction of a fireplace; and secondly, 

 to see how these objects can best be attained. 



Now the design of a chimney fire being simply to 



