Figs. 4 and 5 give plans of the ground floor and first story, and Figs. 1, 2, and 3 give vertical sections.  The second story is arranged like the first, and serves as a drier.  As we have said, there is a double series of chambers for carbonization, drying, and work generally.  These two series are arranged on each side of a central portion, which contains the heating and ventilating apparatus and a stone stairway giving access to the upper stories.  The heating apparatus is a hot air stove provided with a system of piping.  The rags to be carbonized or the wool to be dried are placed upon wire cloth frames.

The carbonization is effected in the following way:  When the heating apparatus has been fired up, and has been operating for about half an hour, the apertures, i, are opened so as to let the air in, as are also those, m, which allow the hot air to pass into the chambers.  The hot air then descends from the top of the chamber into the wool or rags, and, becoming saturated and heavier, descends and makes its exit from the chamber through an aperture, n, near the floor, whence it flows to the central chimney.  This latter, which is built of brick or stone, contains in its center a second chimney (formed of cast or forged iron pipes) that serves to carry off into the atmosphere the products of combustion from the heating apparatus.  The heat that radiates from these pipes serves at the same time to heat the annular space through which the vapors derived from the wool are disengaged.

The air, heated to 40 deg. or 50 deg., is made to pass thus for several hours, until the greater part of the humidity has been removed.  The temperature is then raised to 80 deg. or 90 deg. by gradually closing the apertures that give access to the ventilating chimney.  In order that it may be possible to further increase the temperature during the last hour, and raise it to 90 deg. or 120 deg., an arrangement is provided that prevents all entrance of the external air into the heating apparatus, and that replaces such air with the hot air of the chamber; so that this hot air circulates in the pipes of the stove and thus becomes gradually hotter and hotter.  The hot vapors that issue from the lower chamber rise into the upper one, where they are used for the preliminary drying of another part of the materials.

The hot air stove should be well lined with refractory clay, in order to prevent the iron from getting red hot, and the grate should be of relatively wide surface.  All the pipes should be of cast iron, and all the joints be well turned.  Every neglect to see to such matters, with a view to saving money, will surely lead in the long run to bad results.

[Illustration:  Plan of works for carbonizing wool. (Scale 1-200.)]