MARKETING SOUTHERX-GROWX SWEET POTATOES. 
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doorway only; additional 2 by 4 pieces should be used to splice the 
stringers, connecting them across the door space. If the car is to 
be loaded solid, the floor should be completed by nailing 1 by 4 
pieces across the connecting stringers. 
HEATING AND VENTILATING CARS. 
Subject to a few exceptions in certain territories, a heater car 
service is not available to southern sweet-potato shipper-. Although 
they are permitted to furnish heat in transit, subject to conditions 
specified in the railroad tariffs, it is not done. It is a common prac- 
tice, however, in extremely cold weather to place a stove in the car 
about 12 hours before it is to be loaded. An oil heater is suitable 
for the purpose, and may be kept burning during loading. The car 
should be loaded as quickly as possible and the doors closed. 
Fig. 16. — Doorway bracing. Three boards should have been used, onefor each layer of hampers. 
Many shippers make it a practice to leave the vents in refrigerator 
cars wide open when the temperature is 40° F., or above, decreasing 
the ventilation as the temperature drops between 40° and freezing, 
and closing all vents when the temperature reaches the freezing 
point. In warm weather ventilator cars are used with all vents 
open. 
LINING CARS. 
In cold weather cars are sometimes lined with building paper. A 
car 8 feet by S feet 6 inches by 36 feet requires approximately 2,250 
square feet of paper to line throughout. Whether or not it should be 
completely papered, as shown in Figure 17. or only partially papered. 
depends upon the type of car and its condition. If it is necessary 
to use a ventilator car it should be papered throughout. Refriger- 
ator cars are ordinarily papered only over the ends, the floor, and 
as high as the load on the sides. Two thicknesses of paper are often 
used on the ends and across the doors. All seams should lap at least 
