486 Of Chimney Fireplaces. 



vapour, and to examine the laws of their motions, and 

 the necessary consequences of their being rarified by 

 heat, will perceive that it would be as much a miracle 

 if smoke should not rise in a chimney, all hindrances 

 to its ascent being removed, as that water should refuse 

 to run in a syphon, or to descend in a river. 



The whole mystery, therefore, of curing smoking 

 chimneys, is comprised in this simple direction ; find 

 out and remove those local hindrances which forcibly prevent 

 the smoke from following its natural tendency to go up the 

 chimney ; or rather, to speak more accurately, which pre- 

 vent its being forced up the chimney by the pressure 

 of the heavier air of the room. 



Although the causes by which the ascent of smoke in 

 a chimney may be obstructed are various, yet that cause 

 which will most commonly, and I may say almost uni- 

 versally, be found to operate, is one which it is always 

 very easy to discover, and as easy to remove, the bad 

 construction of the chimney in the neighbourhood of the 

 fireplace. 



In the course of all my experience and practice in 

 curing smoking chimneys, and I certainly have not 

 had less than five hundred under my hands, and among 

 them many which were thought to be quite incurable, 

 I never have been obliged, except in one single instance, 

 to have recourse to any other method of cure than 

 merely reducing the fireplace, and the throat of the 

 chimney, or that part of it which lies immediately above 

 the fireplace, to a proper form and just dimensions. 



That, my principles for constructing fireplaces are 

 equally applicable to those which are designed for burn- 

 ing coal, as to those in which wood is burned, has lately 

 been abundantly proved by experiments made here in 



