The refrigerator itself consists of a number of zigzag or spiral tubes, immersed in a tank-con structed of nonconducting substances. Each one of the zigzags receives an equal supply of liquid ammonia from the distributor. The small tubes conve) lug this supply are shown at p. The vessels r to be refrigerated are sustained on a carriage, which is slid to and fro by the same power that works the pump g', by which the re-saturated solution of ammonia is returned to the boiler. The space in the tank surrounding the zigzags and the water-vessels is filled with an nncongealable liquid, such as alcohol, or a solution of chloride of calcium. The ammonia in the zigzags g dis charges in a vaporized form into the collector a, and passes through the tube t to the cylinder u, where it extends nearly to the bottom of the vessel, and there discharges the gas into the water which baa been brought from the bottom of the boiler a, and partially fills the cylinder u. From this water, the ammonia has been nearly exhausted, and it therefore greedily absorbs the gas ejected into it by pipe t. On the left of vessel u, is a water-level indicator. Within the vessel a, is a worm which receives water by the pipe a' from the elevated reservoir z; after passing to the bottom of the spiral, the pipe curves upward, and then (marked b) descends nearly to the bottom of the vessel y, where it discharges.
The water from the boiler a passes by pipes w to the coolers x y, before reaching the vessel u, where it re-absorbs ammonia. Between the boiler a and the vessel a, the water is cooled so as to fit it for absorbing gas more freely. The pressure in the boiler is sufficient to expel it when the stop-coek w is opened. The vessel x is formed of two concentric cylinders, between which are two spiral tubes, formed of the pipe w continued, and these spirals are immersed in a liquid which fills the annular space between the cylinders, and is the reconstituted ammoniacal solution on its way from the absorber a to the boiler a. From x, the water in the spiral is conveyed in the pipe w, still continued in a single spiral ascending in the vessel y, and continued farther in a pipe w, alongside of the absorber u, where it discharges into a sieve a, and from which it descends in a shower. The exhausted solution from the boiler flows freely by the pipe w to the absorber a, passing the coolers x y, as described ; but it requires some power to force the reconstituted solution back from the absorber u through the pipe f to the boiler. This power is a pump y', driven by a steam-engine or other motor, taking the saturated solution from the absorber by pipe h', and discharging it by pipe into the vessel x, whence it passes by pipe f to the dome abovo the boiler. Gas finding its way into the pump is discharged into the upper part of n. A pipe e" leads to the enveloping-tube o, wbenoe water is conducted by for the use of the ice-vessels r. As the water passes through u,
it is cooled by the ascending vapours of ammonia. In starting the machine, it is first blown through to expel the air. The air escaping from the vessel a passes by the pipe c to the purger d, and beneath the surface of the water therein, which retains any escaping ammonia.
'Holden's (of Philadelphia) machine is adapted to the use of almost any volatile liquid, whether ether, ammonia, carbon bisulphide, &c. The refrigerator-cylinder, Fig. 838, is covered with a non-conducting aubstanoe. It is journalled on a longitudinal shaft A, provided with radial arms B, which carry upon their outer ends longitudinally arranged ribs C. Around these ribs, and near the inner periphery of the cylinder, is wound a continuous coil-pipe D, in which circulates strongly saturated brine, or other non-oongealable liquid, which is received from a convenient cistern or tank. A coil of pipe extends the entire length of the oylinder, and, at each end, oommnnioatea with the hollow ends of the shaft A, and through this hollow with the supply-pipe E, and the exit-pipe F, so that a continuous circulation of the non-congealable liquid may be kept up in the coil. Inside this oylinder, the volatile liquid is placed. It is introduced through a pipe G, and is maintained at such a level as to immerse the bottom portion of the coil of pipes, whioh level may be regulated by means of a glass gauge upon the outside. As the coil of pipes is revolved, the coil passes to the upper portion of the cylinder with ita surface moistened by the volatile liquid, which it carries up from adhesive attraction ; and as the cylinder is exhausted of its gaseous contents through the pipe H by means of pumps, the evaporation of the liquid upon the surface of the coil rapidly takes place to supply the partial vacuum, and a corresponding reduction of tho temperature of the pipes and its contained vehicle of non-congealable liquid takes place. To guard against leakage, which would prevent the best action of the pump in effecting evaporation, the ends of the shaft A are provided with stuffing-boxes, while the outer parte of the bearings are enlarged to form water-boxes, which are filled with the non-congealable liquid, and these, together with the stuffing-boxes, effectually aeal the bearings against all leakage of air in the interior.
As the gas is exhausted from the cylinder, it passes to the pumps previously referred to, thence to a condenser, and thence through a pipe (ae liquid) to a receiver. The cooled non-congealable liquid passes into the case M, Fig. 829, through the pipe F, and thence back to the coil in the cylinder through the pipe E. The circulation of liquid is effected through a circulating-pump, whioh is operated by the engine which works the large pumps, the refrigerator-coil, and a rotary blower for oiroulating air in the congealing-case.