HORIZONTAL ROTARY RETORT.

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Gain in the quantity of gas .—A large increasein the quantity of gas obtained, is a natural conse-quence of the mode in which the decomposition ofcoal is effected by means of the horizontal rotaryretort.

Every body knows that coal, when decomposedslowly, affords a larger quantity of tar ami ammo-niacal liquor, but a less quantity of gas than whendecomposed rapidly.

In the former case, the formation of the proxi-mate products which coal is capable of furnishingis effected properly; the bituminous part of thecoal is developed under the most favourable cir-cumstances.

But when coal, after being previously deprivedof moisture, is very suddenly heated to a high tem-perature, in thin strata, and small portions at a time,so that the vaporous products instead of becomingcondensed, are made to come into contact with asubstance (which in this case is the roof of the retort,)kept constantly at a temperature rather higherthan that at which gold, silver, and copper melts,(32°, \\ edgwood, or 5237°, Fahrenheit,) a verydifferent arrangement of principles takes place,

K