CONSTRUCTION OF RETORTS. 95 



necessary. This large quantity is owing to the incomplete setting and the 

 unnecessary thickness of the retort itself ; and if we allow that an increase of 

 1000 cubic feet of gas may be obtained from a ton of coal by distilling it in 

 a brick oven instead of an iron retort, we shall arrive at the following costs 

 by each process. 



One bench of five large York Ds will carbonize two tons of coal in twenty- 

 four hours ; each ton will yield, say 8000 cubic feet of gas, with ten cwt. of 



coal as fuel 



s. d. 

 Two tons of coal, at 20*. per ton 200 



Fuel 25 per cent. 10 



Wear and tear of retorts for 24 hours - - 026 



Cost for 16,000 cubic feet - - 2126 



which is equal to nearly 3s. 3^d. per thousand. 



Two brick ovens will carbonize the same quantity, viz. two tons in twenty- 

 four hours, and produce, say 9000 cubic feet of gas from each ton, with one 



ton as fuel 



a. d. 



Two tons of coal, at 20*. per ton 200 



Fuel 50 per cent. 100 



Wear and tear of ovens 006 



Cost of 18,000 cubic feet - - 3 6 



which is equal to nearly 3s. 4%d. per thousand ; giving three farthings per 

 meter in favour of iron retorts. 



I have taken neither labour, purifying, leakage, nor interest on capital into 

 consideration, supposing them to be the same in both cases. 



