Fruits which are picked green, or before ripening, mature or ripen while stored. The tendency to decay in ripe fruits is arrested by refrigeration. Upon exposure to heat and air the usual process goes on more rapidly than in foods which have not been refrigerated. Food should enter into consumption with little delay when taken out of cold storage. The length of time during which it is desirable to keep goods in cold storage may be best determined practically with reference to the ends sought to be attained in any particular case. THE PRINCIPLES OF COLD STORAGE.--Refrigeration depends upon the circulation of pure, dry cold air. It is based upon natural laws, which are well known and readily observed. Air exposed to heat is expanded in volume; it is thus made lighter and will rise, being forced upward by the surrounding cooler air. Air exposed to cold is condensed and made heavier; it will then gravitate to lower levels. The capacity of air for absorbing and retaining moisture varies with its temperature. Warm air will sustain a considerable amount of vapor, which will be condensed and precipitated if the air is cooled. As water is cooled and brought to the freezing point it expels a large part of the heat gathered at a higher temperature. As ice is melted to water this process is reversed, and heat and air are reabsorbed. The operation of these natural laws is taken advantage of in refrigeration. As usually constructed, cold storage ice houses are built with two stories; the first floor for storing goods, the second filled with ice. The floor between is arranged with openings, through which the air, chilled by contact with the ice, descends into the store room. A flue is provided to conduct the warm air to the upper part of the ice chamber, when it is dried and purified by contact with the ice as it descends on being chilled. Drains and traps are required to carry off the meltage water, and to secure the water condensed from the warm air. Dampers in the cold and warm air flues assist in controlling the circulation, and ventilators placed in the roof keep the loft free from dampness. The walls, ground floor and ceiling are constructed as nearly non-conducting of heat and cold as practicable. No cracks or any channels are permissible by which air can enter. Drains which take out the water are securely trapped, to keep out the air. Vestibules with perfectly fitting doors are placed at all entrances. Windows are fitted with three or four sashes and air spaces between.