REFRIGERATION OF DRESSED POULTRY IN TRANSIT. 17 
The indices of efficiency obtained by the use of the foregoing 
formula have served as a basis on which to compare cars of different 
construction. They are not claimed to be an accurate expression 
of the resistance of the car to heat transmission nor of its exact 
capacity for utilizing the refrigerant supplied. To obtain figures 
mathematically and physically exact would necessitate the record- 
ing of the amount of ice and salt used during the period of observa- 
tion and other data not readily secured from cars in commercial 
service. It is highly desirable that such accurate figures should be 
obtained, and it is hoped that the information which this report is 
able to furnish may lead to the compilation and utilization of such 
data. 
COMPARISON OF CAR EFFICIENCY. 
The magnitude of the field of operation covered by this investi- 
gation and the complexity of the factors uniting to determine the 
efficiency of the refrig- 
erated carrier made it 
highly desirable that 
some concrete expres- 
sion be worked out 
whereby a comparison 
of the various types of 
cars studied might be 
made. 
The application of 
the formula to the 
cars used in the ex- 
perimental shipments 
results in a wide dif- 
ference of efficiency 
indices (see Table 5) 
for the various types 
of cars. All of the 
cars of type A are 
identical hi original construction and are operated by a single 
company. The cars of type B are alike in ice bunkers and insula- 
tion, but, belonging to a different series, they vary in size. The 
cars of type C are all of the same dimension; likewise those of type D. 
Each type is operated by one railroad or car company. The four 
types are unlike each other hi many of the essential elements of 
refrigerator construction, such as the kind and thickness of insu- 
lation, its manner of application, ice bunkers, and doors. For the 
sake of a clearer understanding, the efficiency indices of Table 5 are 
presented graphically as figure 4, in which the height of the columns 
increases directly as the efficienc} T . 
7078°— Bull. 17—13 3 
Fig. 4.— Comparative efficiency of cars of types A, B, C, and D. 
