TCF.-HO USES.

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effecting the ice. Unless the ground is composed of porous materials, as sand or gravel, it isnecessary to use a heavy bed of broken stone, slag, cinders, or ashes, to afford better drainage.

Fig. 157.—Cross-section.

Fig. 158.—Cross-section.

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In the coal regions coal dirt is used very extensively for this purpose, with good results. Ontop of the bed thus prepared it is customary to lay a loose floor of rough plank or mill slabs.It is preferable, however, to place this floor on mud-sills or scantlings in such a way as to leavean air-space below, which insures better drainage under the ice and assists to insulate the icefrom the heat of the earth. A layer of sawdust, brush, or similar material is spread on top ofthis floor. It is a very common mistake in building ice-houses to simply level off the groundand lay down boards with a layer of sawdust on top to form the bed, the whole being sur-rounded by water-tight masonry walls or earth embankments. The result is that the bottomlayers of ice are constantly in water, and hence melt much faster.

The top of the bedding material, whatever it be, should be dished from all sides towardthe centre of the house or toward the centre of each compartment, if the house is divided intocompartments, so as to give better drainage. An additional reason for this is, that, if the massof ice should have a tendency to slide on its bed, the resultant pressure would more likely betoward the centre of the mass, and detrimental movements toward the sides of the buildingwould be prevented. The side walls and partitions are frequently tied together by wrought-iron rods, so as to be better able to resist the pressure of the ice, in case it should move in abody and bring an outward pressure on the walls.

To facilitate the handling of the ice into and out of the house, doors should be arrangedat different levels, or else one door provided leading into a shaft inside the building, the sidesof the shaft being formed of loose boards, which can be adjusted to suit the change of levelof the ice. A double set of doors are better than a single door, as in the first case an air-space is formed between the doors when closed. Large ice-houses are divided into compart-ments, so that the ice is only exposed in one compartment at a time when the doors have tobe opened.

Small amounts of ice are handled by means of a tackle hung from a beam projecting outfrom the building over the doors. Where large amounts of ice are handled daily, or whilestocking the house, it will be more economical to provide a small hoist, cage, elevator, ortraveller, operated by steam or horse power, arranged to dump the blocks of ice automaticallywhen the proper level is reached.

The erection of an artificial-ice plant has, as far as the author knows, never been under-taken by railroad companies. Having studied the question very carefully from the theo-retical, practical, and industrial standpoints, the author is firmly convinced that the intro-duction of an artificial-ice plant on a railroad, especially in southern sections of the country,