352 THE CANADIAN NATURALIST. [Yol. X. 



The total annual value of the 2:as-works by-products may be 

 estimated as follows : — 



Coloring matter £3,350,000 



Sulphate of ammonia 1,947,000 



Pitch (355,000 tons) 365,000 



Creosote (25,000 gallons) 208,000 



Crude carbolic acid (1 ,000,000 gallons) .... 100,000 

 G-as coke, 4,000,000 tons (after allowing 

 2,000,000 consumption in working the re- 

 torts) at 12s 2.400.000 



£8,370,000 



Taking the coal used, 9,000,000 tons, at 12s., equal £5,400,- 

 000, it follows that the by-products exceed in value the coal used 

 by very nearly £3,000,000. 



In using raw coal for heating purposes these valuable products 

 are not only absolutely lost to us, but in their stead we are 

 favoured with those semi-gaseous by-products in the atmosphere 

 too well known to the denizens of London and other large towns 

 as smoke. Prof. Roberts has calculated that the soot in the pall 

 hanging over London on a winter's day amounts to fifty tons, 

 and that the carbonic oxide, a poisonous compound, resulting 

 from the imperfect combustion of coal, may be taken as at least 

 five times that amount. Mr. Aitken has shown, moreover, in an 

 interesting paper communicated to the Royal Society of Edin- 

 burgh last year, that the fine dust resulting from the impecfect 

 combustion of coal is mainly instrumental in the formation of fog; 

 each particle of solid matter attracting to itself aqueous vapour ; 

 these globules of fog are rendered particularly tenacious and dis- 

 agreeable by the presence of tar vapour, another result of imper- 

 fect combustion of raw fuel, which might be turned to much 

 better account at the dye-works. The hurtful influence of smoke 

 upon public health, the great personal discomfort to which it 

 gives rise, and the vast expense it indirectly causes through 

 the destruction of our monuments, pictures, furniture, and 

 apparel, are now being recognized, as is evidenced by the 

 success of recent Smoke Abatement Exhibitions. The most 

 effectual remedy would result from a general recognition of 

 the fact that wherever smoke is produced fuel is being con- 

 sumed wastefully, and that all our caloric effects, from the 

 argest down to the domestic fire, can be realised as completely, 



