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during freezing. The cells are flat and constructed of galvanized iron, so as to form a hollow space of about 2 in. in width, through which cold brine is circulated by a pump. They are placed vertically in a tank, the distance between them being from 8 to 14 in., according to the thickness of the ice to be produced. The tank is filled with water, which is kept in agitation by means of a reciprocating paddle or piston; in this way the air escapes, and with pro er care a block of great transparency is produced. To thaw it off? warm brine is circulated through the cells. A usual size for cell ice is 4 ft. by 3 ft. by I ft. mean thickness, the weight being about 6 cwt. If perfect y transparent ice is required, the two sides of the block are not allowed to join up, and it is then called plate ice, which is often made in very large blocks, afterwards divided by saws or steam cutters. In such cases the evaporation of the ammonia or other refrigerating liquid frequently takes place in the cells themselves, brine being dispensed with. With a well constructed can ice-plant of say 25 tons capacity per day, from I5 to 16 tons of ice should be made in Great Britain to a ton of best steam coal. For cell and plate ice the production is considerably below this, and the first cost of the plant is much greater than that for can ice.

Fig. 7 shows an arrangement of cold storage on land, refrigerated on the air circulation system. The insulated rooms, on two floors,

are approached by corridors, so as to exclude external air, which if allowed to enter would deposit moisture upon the cold goods. The air cooler is placed at the end, and the air is distributed by means of wood ducts furnished with slides for regulating the temperature of the rooms, which are insulated according to the method shown in fig. 5. In some cases, instead of the entrance being at the sides or ends, it is at the top, all goods being raised to the top floor in lifts and lowered by lifts into the rooms. With good machinery the cost of raising is not great, and is probably equalled by the saving in refrigeration, since the rooms hold the heavy cold air as a glass holds water. Large passenger vessels and yachts are now generally fitted with refrigerating machinery for preserving provisions, cooling water and wine, and making ice. Usually two insulated compartments are provided, one for frozen meats at about 20° F., and one for vegetables, &c., at about 4o°. They have a capacity of from ISOO to 3000 cub. ft. or more, according to the number of passengers carried, and they are generally cooled by means of brine pipes, though direct expansion and air circulation are sometimes adopted. A passenger vessel requires from 2 to 4 cwt. of ice r day. On battleships and cruisers the British Admiralty use smagiompressedair machines for ice-making, and larger machines, generally on the carbonic-acid system, for cooling the magazines. A modern frozen meat-carrying vessel will accommodate as much as 120,000 carcases, partly sheep and partly lambs, requiring a hold capacity of about 300,000 cub. ft. In some vessels both fore and aft holds and 'tween decks are insulated. Lloyd's Committee now issue certificates for refrigerating installations, if constructed according to their rules, and most modern cargo-carrying vessels have their refrigerating machinery classed at Lloyd's. In the meat trade between the River Plate, the United States, Canada and Great Britain, ammonia or carbonic acid machines are now exclusively used, but for the Australian and New Zealand frozen meat trade compressed-air machines are still employed to a small extent. The holds of meat-carrying vessels are refrigerated either by cold air circulation or by brine pipes. A ' " Though the adoption of refrigerating and ice-making machinery for industrial purposes practically dates from the year 1880, the manufacture of these machines has already assumed very great proportions; indeed, in no branch of mechanical engineering, with the exception of electrical machinery, has there been so' remarkable a development in recent years. The sphere of application is extending year by year. The cooling of residential and public buildings in hot countries, though attempted in a few cases in the United States and elsewhere, is yet practically untouched, the manufacture of ice and the preservation of perishable foods (apart from the frozen and chilled meat trades) have in many countries hardly received serious consideration, but in breweries, dairies, margarine works and many other industries there is a large and increasing field for refrigerating and ice-makin machinery. A recent application is in the cooling and drying otg the air blast for blast furnaces. Though this matter had been discussed for some years, it was only in 1904 that the first plant was put to work at Pittsburg.

For further information reference may be made to the following: Siebel, Compend. of Mechanical Refrigeration (Chicago); Redwood, Theoretical and Practical Ammonia Refrigeration (New York); Stephansky, Practical Running of an Ice and Refrigerating Plant (Boston); Ledoux, Ice-Making Machines (New York); Wallis-Taylor, Refrigerating and Ice-Making Machines (London); Ritchie Leask, Refrigerating Machinery (London); De Volson Wood, Thermodynamics, Heat Motors and Refrigerating Machinery (New York); Linde, Kdlteerzeugungsmaschine Lexikon der gesamten Technik; Behrend, Eis und Kalteerzeugungs-Maschinen (Halle); De Marchena, Kompressions Kaltemaschinen (Halle); Theodore Koller, Die Kdlteinduslrie (Vienna); Voorhees, Indicating the Refrigerating Machine (Chicago); Norman Selfe, Machinery for Refrigeration (Chicago); Hans Lorenz, Modern Refrigerating Machinery (London); Lehnert, Moderne Kdltetechnik (Leipzig)? L. Marchis, Production et utilisation du froid (Paris); C. Heinel, Ban und Betrieb von Kdltemaschinen Anlagen (O1denburg)§ R. Stetefeld, Eis und Kdlteerzeugungs-Maschinen (Stuttgart). (T. B. L.)

REGAL, a small late-medieval portable organ, furnished with beating-reeds and having two bellows like a positive organ; also in Germany the name given to the reed-stops (beating-reeds) of a large organ, and more especially the “ vox humana ” stop. The name was not at first applied to the small table instrument, but to certain small brass pipes in the organ, sounded by means of beating-reeds, the longest of the 8-ft. tone being but 5% in. long. Praetorius (1618) mentions a larger regal used in the court orchestras of some of the German princes, more like a. positive, containing 4-ft., 8~ft. and even sometimes 16~ft. tone reeds, and having behind the case two bellows. These regals were used not only at banquets but often to replace positives in small and large churches. The very small regal, sometimes called Bible-regal, because it can be taken to pieces and folded up like a book, is also mentioned by the same writer, who states that these little instruments, first made in Nuremberg and Augsburg, have an unpleasantly harsh tone, due to their tiny pipes, not quite an inch long. The pipes in this case were not intended to reinforce the vibrations of the beating-reed or of its overtones as in the reed pipes of the organ, but merely to form an attachment for keeping the reed in its place without interfering with its functions. The beating-reed itself in the older organs of the early middle ages, many of which undoubtedly were reed organs, was made of wood; those of the regal were mostly of brass (hence their “ brazen Voices ”). The length of the vibrating portion of the beating-reed governed the pitch of the pipe and was regulated by means of a wire passing through the socket, the other end pressing on the reed at the proper distance. Drawings of the reeds of regals and other reed-pipes, as well as of the instrument itself, are given by Praetorius (pl. iv., Xxxviii.). H

There is evidence to show that in England, and France also, the word “regal ” was applied to reed-stops on the organ; Mersenne (1636) states that “ now the word is applied to the vox humana stop on the organ.” In England, as late as the reign of George III., there was the appointment of “ tuner of the regals ” to the Chapel Royal.

The reed-stops required constant tuning, according to Praetorius, who lays special emphasis on the factithat the pitch of the reed-pipes alone falls in summer and rises in winter. During the 16th and 17th centuries the regal was a- very great favourite, and. although, owing to the civil wars and the ravages