246 Jordan on the Floaluge of 



whilst I have been observing, these have been changed to that 

 state of vapour which is called, and considered as, burned 

 smoke. What, however, is intended by a fire burning its own 

 smoke? Does it mean the annihilation of all and every particle 

 of coal thrown on the fire ? Nothing can be more unphilosophi- 

 cal than this supposed destruction of ultimate aggregate par- 

 ticles, this annihilation of matter; and the particles, under 

 whatever form rising, and rise they must, will again be preci- 

 pitated. The precipitation of all that rises is of necessity, and 

 perhaps the black form of undecomposed coal is the least 

 injurious. 



When a given quantity of coals is thrown on a fire, and 

 after combustion a few ounces of ashes remain in the hearth, 

 what has become of the remainder ? It has ascended the chim- 

 ney in the form of vapour, at first black, and afterwards grey, 

 white, colourless, or transparent. The proposal to burn the 

 smoke, or black vapour, assumes, that the black vapour is 

 more noxious than the others, and this requires proof. Upon 

 reflection, it would appear, that minute parts of the coal, 

 simply divided so as to float in air, would be less noxious than 

 the more active and offensive parts when decompounded. Of 

 whatever colour the particles are, they ascend the chimney, 

 and unless annihilated, are precipitated, and nothing is gained 

 by this notable project of consuming smoke, but change of 

 appearance in the vapour, and a precipitation perhaps more 

 noxious. Of this, experiments may decide, but the decision 

 promises to be of so little use as not to require the skill and 

 industry of the chemist. As long as any fire continues to burn 

 with or without flame, there is an emanation of heated particles, 

 of particles of the air, and of the body, by whose union with air 

 the heat is developed and continued. This may be per- 

 ceived by the change of figure produced in bodies seen through 

 them. The particles of the body are almost in a state of 

 solution in the heated air, and, together with the heated air, 

 change the places of bodies looked at through them. Ignited 

 stacks of bricks exhibit these appearances after the gross smoke 

 has passed away. 



