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ADVANTAGES OF THE

rotary retorts, with the cost and deterioration of a setof cylindrical, parallelopipedal, ellipsoidal, or semi-cylindrical retorts of an equal power, (that is to sayto produce a like quantity of gas, in a given time,)a difference not less striking presents itself infavour of the horizontal retort.

We have stated already, that cylindrical, ellipsoi-dal, parallelopipedal, or semi-cylindrical retorts,when constantly kept in action, and worked to thegreatest advantage, cannot be made to last longerthan six months.*

Only one-third part of the top and bottom platesof the rotary retort being exposed to the actionof heat, are alone liable to deterioration. It isonly necessary therefore that these parts of thevessel be renewed, while the other parts remainuninjured for years. The new top and bottomplates being rivetted to the old and undecayedpart, without deranging the rest, the retort isrendered as good as new.

* They are frequently rendered unfit for use in three months, andat some works in two months, owing not less to the irregularity ofthe temperature at which they are worked, than to the carelessness ofthe workmen.