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DIFFERENCE IN THE QUANTITY

When larger retorts are employed for decompo-sing coal in masses, from five to ten inches in thick-ness, the loss of heat is in a much greater ratio.

In the hope of remedying in some measure theevils thus distinctly ascertained to arise from theundue thickness of the masses of coal subjected tothe distillatory process, there have not been want-ing manufacturers who have had recourse to expe-riments on a large scale, to ascertain with certaintywhether they might not be gainers by suffering thedistillatory process, when the retorts are chargedwith two bushels of coal, to proceed only for thespace of six hours, instead of eight. But the resultof these experiments, as will be presently explained,has shown satisfactorily that it is more profitableto keep up the distillatory process for a period ofeight hours, with the retorts fully charged, than toabridge the operation by terminating it at the endof six hours.

Others again, have imagined, that it would bemore economical to decompose a less quantity ofcoal at once, or to decrease the thickness of thestratum of coal in the cylindrical, or in any of thebefore named retorts ; but then again, serious diffi-