f, Fig 60, is a manometer, which indicates the degrees of pressure exerted by the steam in the interior of the boiler. It consists of a wrought-iron pipe bent double, and is filled with mercury 1.22 meter (4.002 feet) high counted from its base. One end of the pipe communicates with the boiler, while the other end is provided with a small brass wheel. Upon the latter is a thread of twisted silk, to the end of which is suspended an iron cylinder of somewhat smaller circumference than the bore of the pipe, so that it can move up and down in it without friction. This cylinder rests always upon the mercury. To the other end of the thread is fastened an indicator of somewhat less weight than the cylinder, which, by sliding in a groove in a graduated board placed alongside the pipe, indicates the degrees of steam pressure.
g is a cast-iron pipe for heating the drying room, and
h another cast-iron pipe for heating the store-room for the bones.
i is the forcing pump for feeding the boiler with water.
k is a sheet-iron reservoir placed close to the end of the boiler. It is filled with water, which is heated by the heat lost in the fire-place in consequence of the draught, and by allowing the smoke to circulate under the reservoir before passing into the chimney. The reservoir communicates with the forcing-pump by means of a pipe and stopcock, so as to avoid feeding the boiler with cold water.
l is the fire-place, consisting of the grate, door and cast-iron frame.
The drum, e, is a spherical vessel of strong sheet-iron doubly riveted. It is 3 meters (9.84 feet) in diameter, and capable of resisting a pressure of six to seven atmospheres. It serves for softening the bones with the assistance of steam passed into it from the boiler, a. It is provided with a manhole similar to that of the boiler.
n is a wrought-iron shaft passing horizontally through the drum and revolving in the brasses, o.
g, Fig. 61, is a gearing with a crank, by means of which the drum e is revolved. The power of the gearing must be so calculated that one man can turn the wheels when the drum is filled with water.
