MECHANICS AND USEFUL ARTS. 125 



TRANSPORTATION OF FRESH MEATS AND FRUITS, ETC., THROUGH 

 LONG DISTANCES. THE DAVIS REFRIGERATOR CAR. 



The shell of the car consists exteriorly of the ordinary wood 

 casing. A second wooden shell is made smaller than the first, 

 and placed within it so as to leave an air space or chamber 

 entirely around the top, bottom, and sides of the car. Within this 

 second shell is placed a layer of hair, about 2 inches in thick- 

 ness, and this again is lined with an interior wooden shell. This 

 construction makes a non-radiating and non-conducting compound 

 shell or case, of great power to resist the action of external heat, 

 and renders the expenditure of ice quite small to maintain the 

 required depression of temperature, after the interior of the car 

 and its contents have been cooled clown to the proper point, say 

 from 34 to 38 Fah. 



The refrigeration is accomplished in the following manner : 

 Along the sides of the car are placed sheet-metal tanks shaped 

 like the frustra of very gradually tapering wedges. They extend 

 from the top to the bottom of the car, and are about 5 inches 

 thick at the top and 2 inches at the bottom. These tanks com- 

 municate at the top with the exterior of the car through funnel 

 or hopper-shaped openings, and at the bottom through drip-pipes, 

 which convey awa}^ the moisture. The funnel-shaped openings 

 at the top are used for putting in the refrigerating mixture, con- 

 sisting of broken ice and salt, and are provided with air-tight cov- 

 ers. The car is entered through a hatchway at the top, through 

 which its freight is also introduced. This hatchway is also pro- 

 vided with a tight-fitting cover, made non-radiating and non-con- 

 ducting, like the sides of the car. 



The store of ice and salt for the trip is contained in a separate 

 department in one end of the car, so that its contents can be 

 reached, and the refrigerating tanks supplied, without opening the 

 freight-room. 



The freight is placed in the car on strips of board, strips of 

 board also preventing its coming in contact with the walls of the 

 refrigerating tanks. The packages are also so placed as to leave 

 interspaces through, between, and around each. During the 

 process of refrigeration the air circulates around the packages and 

 nlong the sides of the tanks like water in a steam-boiler, the colder 

 air falling, and the warmer air rising to the top, becoming chilled 

 in its passage along the sides of the tanks, and depositing its 

 moisture on the tanks till their sides are covered with a thick 

 stratum of congealed water or hoar-frost. Thus the air is not 

 only cooled but dried, no accession of moisture being derived 

 from the external air or from the ice in the tanks, with either of 

 which the interior of the car has no communication so long as the 

 car is kept closed. 



The two essentials for the preservation of substances liable to 

 ferment, namely, absence of heat and of moisture, are thus se- 

 cured in a veiy perfect manner, and the arrangement of the tanks 

 is such that the space within the car for the storage of freight is 

 not materiallv reduced. Some addition to the refrigerative mix- 



/ O 



