16 



USE OF DAMPERS. 



may return within a few inches of the former, and in both cases the smoke 

 will escape through the back wall near to the furnace. Two narrow flues 

 are better than one broad one of a capacity equal to both. In narrow 

 flues, the velocity of heat is much greater than in broad ones, therefore, it 

 sooner reaches the end farthest from the fire, and consequently maintains 

 a more regular degree of temperature between both ends of the house. 

 Flues should never, if it can be avoided, be built upon the top of each other ; 

 neither should they be placed at too great a distance from the front of 

 the house, which is in all houses the coldest part. If a flue be placed in 

 the centre of a house, it would appear at first sight, from the well kno^Ti 

 property of heat, that it would radiate equally from each point, and 

 that the centre of the house would be the most proper situation for 

 the flue to be placed in. That the heat would radiate in this manner, 

 is quite true ; but the lower and front part of the house being colder than 

 any other parts, the pressure of the cold air would be so great, that 

 the particles sent oiF by radiation from the flue, would be unable to 

 resist it with suflacient force. It Tvill, consequently, remain the coldest 

 part of the house, and, therefore, the most proper situation for the flues 

 to be placed in. 



The use of dampers have been recommended, and these have been of 

 various constructions: the object to be attained by them is to regulate the 

 heat in the flue, and also to prevent its escape from the chimney top, 

 by confining it in the flue and causing it to escape into the house through 

 the bricks. This would no doubt be all very well, if we were certain of 

 the purity of the heat so enclosed, or if there were a total absence of 

 expansibility in the natm*e of heat ; but if heat be so enclosed, it is apt to 

 expand to that degree, that the flues would not be able to contain it, and 

 an explosion might be the consequence, which might prove destruction to 

 the whole contents of the house. The best mode of regulating flues is 

 decidedly the proper use of a good fm-nace, with double doors and an 

 ash pit register. With such an apparatus and a weU constructed flue, 

 eveiy ol>ject of the cultivator may be accomphshed. 



