REFRIGERATOR CARS.--A cursory view of the cars in any freight yard discloses a decided difference in the appearance and thoroughness of construction among them. Those styled refrigerator cars fare very much better than their companions. A critical examination shows that these cars are models in all details of construction, and their finish casts the ordinary freight cars far in the shade. The main features of these cars are found, first, in their walls, including floors and ceilings, which are variously made of combinations of filled and air sections, with paper and felt linings; second, an ice tank placed, sometimes at one, or both ends, and in others in the roof of the car; third, in the regulation of the air supply, or ventilation. Some very elaborate designs have been made, covering the features necessary to the successful working of these cars. Most of them are patented. The floor, ceiling and walls have several sections, the outer being usually an air space, or a space filled with thick hair felt. Following is a compartment filled with pulverized charcoal, or other non-conducting filling. This compartment is faced with carefully matched lumber lined with paper. The walls are about six inches thick all together. The doors are the same thickness as the walls, with beveled edges, which wedge into the frame as the door is closed. A fastening is used that is so made that a strong pressure is brought against the door, forcing it into its seat, and an extra precaution taken by inserting a strip of cotton flannel between the door and frame, which thoroughly excludes air and dust. In the best constructed cars there is no chance for direct contact of the cooled air with the ice. This of special is importance in cars in which fresh meat, butter, and other articles, are carried, which are absorbents. Where the ice tank is located in the roof of the car, the circulation of air is secured by gravity, and is changed by admission of air through an opening so arranged that a draft is created by the motion of the car. Very fine brass wire cloth is doubled over these openings, to exclude the dust; as the air enters, it is discharged against a water surface, which catches the fine dust carried through the screens. The waste water is discharged through a trap, which effectually shuts off the entrance of air. When the ice tanks are placed at the ends of the car gravity will not maintain a circulation of air. As the ice melts, the upper strata of air remains warm. To avoid this feature, resource is had in a forced draft. The air in the upper part of the car is collected by a fan and forced through tubes extending through the ice tanks and opening on to the floor of the car. In connection with the fan is an inlet and outlet tube, by which a gradual change of air is effected.