8S; 



and a half, and I imagine few instances occur where a higher 

 temperature is required, I should now conclude this disquisition 

 which has already exceeded its proper limits, yet I am induced 

 to trespass still more on the indulgence of the Academy and give 

 a succinct account of another species of furnaces, which is as im- 

 portant to the manufacturer as the air furnace is to the chemist • 

 I mean that which acts by the combustion of coal gas, being in 

 fact but a blow-pipe on a large scale, and to which the French 

 in their zeal for appropriation have given the name of fumivore. 

 They are of indispensable use where large quantities of ma- 

 terials are to be heated, and their improvement is beneficial, not 

 merely to the manufacturer who employs them, but to all in their 

 vicinity. What a gloomy spectacle does one of our large towns 

 present to a foreigner, it is covered with a murky shroud of smoke, 

 its edifices are blackened and disfigured, while the very lungs of 

 its inhabitants are stained by the sooty atmosphere which they 

 inhale ! Even a common observer, when he sees a pitchy cloud 

 disgorged from the chimney of a steam engine floating on the 

 wind to an immense distance, views it with disgust as a foul blot 

 in the landscape, and he from whose establishment it proceeds 

 would feel equal annoyance at the sight of it, did he know that in 

 it the most valuable part of his fuel is uselessly evaporated : yet this 

 is actually the case and it is not an exaggeration to say that one 

 third of it is thus lost. Attempts have been made to remedy this 

 nuisance, but have not hitherto been completely successful, at least 

 we may conclude so from the fact that the contrivances which 

 have been proposed are not adopted ; I will therefore give an ac- 

 count of them, and endeavour to ascertain the causes of their 



