n, are cast-iron steam pipes occupying the entire surface of the box, being placed at equal distances from each other, and connected on their ends by semicircular pieces. The steam, which is allowed to circulate in the pipes in order to boil the liquid, enters through one of the ends which rises up vertically and is connected with the cock h´, Fig. 59. The other end is secured to the inner side of the box, which is perforated for the admittance of the cock o´. Upon the steam pipes lies a wooden framework with linen nailed upon it, the object of which is to prevent the comminuted bone substance from falling under the pipes. The frame must, of course, fit closely into the box.
The cock h´ graduated in eight equal parts serves to admit steam into the pipes n´, and is opened either entirely or half, or one-quarter, or one-eighth, according to the stronger or gentler ebullition to be produced.
To prevent the steam from becoming stagnant in the steam pipes n´, a small jet is allowed constantly to escape through the cock o´. The latter serves also to run off the condensed steam when it no longer possesses the heat required to keep up ebullition.
p´, Fig. 62, is a cock in the bottom of the box d´ for drawing off the gelatinous solution from the residue. The box e´, Fig. 62, a ground-plan of which is shown in Fig. 63, serves for evaporating the gelatinous solution, which is effected by circulating steam through several tubular pieces of cast-iron which form the bottom of the box and are connected in a similar manner as the pipes in the box d´.
The cock i is graduated and similar to h´.
Fig. 63.
The cock r´, Fig. 63, is similar to o´, Figs. 59 and 62.
s´, Fig. 63, is a cock for drawing off the evaporated gelatinous solution.