534 Of Chimney Fireplaces. 



consideration to be passed over in silence. A knowl- 

 edge of the cause of the ascent of smoke being indis- 

 pensably necessary to those who engage in the improve- 

 ment of fireplaces, or who are desirous of forming just 

 ideas relative to the operations of fire and the manage- 

 ment of heat, I shall devote a few pages to the investi- 

 gation of that curious and interesting subject. And as 

 many of those who may derive advantage from these in- 

 quiries are not much accustomed to philosophical dis- 

 quisitions, and would not readily comprehend either the 

 language or the diagrams commonly used by scientific 

 writers to explain the phenomena in question, I shall 

 take pains to express myself in the most familiar man- 

 ner, and to use such comparisons for illustration as may 

 easily be understood. 



If small leaden bullets, or large goose-shot, be mixed 

 with peas, and the whole well shaken in a bushel, the 

 shot will separate from the peas, and will take its place 

 at the bottom of the bushel ; forcing, by its greater 

 weight, the peas, which are lighter, to move upwards, con- 

 trary to their natural tendency, and take their places above. 



If water and linseed oil, which is lighter than water, 

 be mixed in a vessel by shaking them together, upon 

 suffering this mixture to remain quiet the water will 

 descend and occupy the bottom of the vessel, and the 

 oil, being forced out of its place by the greater pressure 

 downwards of the heavier liquid, will be obliged to rise 

 and swim on the surface of the water. 



If a bottle containing linseed oil be plunged in water 

 with its mouth upwards, and open, the oil will ascend 

 out of the bottle, and, passing upwards through the mass 

 of water, in a continued stream, will spread itself over 

 its surface. 



