CANNING SARDINES 158 
diffusion takes place, more quickly than if they enter at the other 
end. ‘The drop in air temperature in a tunnel of given size will not 
have to be as great if air is handled in this way. 
Another plan of handling the trucks so as to prevent loss of heated 
air where the trucks enter and leave the cooking tunnel is shown in 
Figure 29. A and B are two vestibules so arranged on a platform 
with rollers that the whole can be shifted from the position shown 
(CD) to the position DE, and back again, as desired. Trucks of 
fish as loaded are run into A. When full, and as soon as all the trucks 
in B have moved into the cooker Ff, the door G is closed and AB is 
moved to the position DE, after which G@ is again opened. While 
the trucks are passing from A to F, more trucks are loaded in B at 
E. The vestibules A and B slope towards F, so that the trucks move 
into F as fast as there is room for them. 
In F the trucks continue to roll forward, down a slight incline, to 
H, where they are picked up by a conveyer and carried up an incline 
at the desired speed and out of the cooker at 7. The hot air is blown 
through the tunnel in the same direction that the trucks move. This 
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Fic. 29 
air can be handled in such a way as to prevent much loss of air at J, 
although the tunnel is open at this point. A window in the end of 
the tunnel at D and a light somewhere in the tunnel near @ will 
enable the operator to know when more trucks should be placed in 
the cooker. 
One firm of drying engineers suggested the use of a cooker in which 
the air is blown at right angles to the direction in which the trucks 
are conveyed. Equipment of this sort is used extensively in drying 
substances where the drying time usually is long and the air velocity 
low. It can be changed, however, to make an excellent cooker. 
In Figure 30 is shown a plan of operation that will give good results. 
The trucks A are made with two solid sides, BB. As they enter 
and leave the cooker they pass through a vestibule, GG, just the size 
of the trucks and a little over one truck width in length. The two 
solid sides prevent loss of air. In the center of the cooker a similar 
arrangement divides it into two parts, through which the air is made 
to travel in different directions in order to give all trucks more or less 
similar heat treatment. If high-pressure steam is used for heating 
