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DESCRIPTION OP THE

flues, and the fire-place. The whole retort isguarded from the contact of the fire, which wouldsoon destroy it, by fire-bricks ; it notwithstandingspeedily receives the full effect of the heat, andretains its temperature when once heated for a longtime. Fig. 1, plate II., exhibits one of the retortsfixed in its furnace. A perspective view of threeretorts may be seen in fig., 2, plate VII.

Through the centre of the retort, passes perpen-dicularly, an iron shaft D, as shown in the sectionof the retort, fig. 2, plate III., and also in fig. 1,plate II. The lower extremity of the shaft re-volves upon the bottom of the retort, in a cup-shapedcavity, w hile its upper extremity passes through theroof of the retort, where the latter is made air-tight by means of a pipeE, fig. 1, plate II., and E,fig. 2, plate III., closed at the top and surroundingthe shaft, and hence the shaft must always pre-serve its centre.

To the lower extremity of the shaft is keyeda box or centre piece, (technically called a rosecentre,) F. fig. 2, plate III. It is also seen in theperpendicular section of the retort, fig. 1, plate II.From this shaft radiate twelve wrought-iron arms,