HORIZONTAL ROTARY RETORT.

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required in the old plan (by means of cylindricalretorts) to the narrowest available limits, therebeing no outward crust of coke to be kept red hotfor hours to no purpose, while the decompositionof the interior mass of coal is going on ;—the cokeitself being as soon as formed removed from thesource of heat, and applied while cooling, to warmup a fresh supply of coal next in order of becomingdecomposed, instead of being discharged in a redhot state, into the open air, as requires to be donein the practice before detailed—the whole fuel inshort being necessarily and beneficially expended—the saving of coal employed as fuel in this respect,is exactly the gaining of all that is lost on the planof employing cylindrical or any of the retorts be-fore described. Hence one chaldron of coal isdecomposed at the gas establishments where hori-zontal rotary retorts are in action by means oftwenty per cent of fuel, and at some establish-ments an expert stoker will work the retortswith fifteen per cent of fuel.

Saving of time .—The saving of time does notmerely amount to what is consequent on the spee-dier decomposition of the coal, and the saving of