UTILIZATION OF THE FISH WASH-; OF THE PACIFIC OCEAN. 47 
mum possible daily output of raw materials from a w * one-line " can- 
nery, amounting to 27,000 pounds, at least four of those would be re- 
quired, a number which scarcely could be operated economically. 
This estimate is based on the supposition that the driers will be op- 
erated only six hours per day. 
There are other forms of steam driers of more or less desirable 
design which could be adapted to the small-scale drying of scrap. 
However, no steam drier should be considered which does not pro- 
vide for evaporation under vacuum or for the removal, at frequent 
intervals or continuously, of the moisture-saturated air. The effi- 
ciency of any other form necessarily must be low. 
We believe that there are other possible forms of apparatus which 
could be operated more economical^, and others again which would 
yield a higher efficiency, but these lack demonstration in actual prac- 
tice and for the sake of conservativeness and fairness to all concerned 
are not recommended here. We have in mind, in this connection, 
continuous mechanical cookers and screw presses, of small capacities, 
capable of rendering in about 6 hours the waste resulting from a 12- 
hour run of the cannery. For a " one-line " cannery, packing 900 
cases per day of 12 hours, it has been seen this would be 18 tons for 
the day, or 6,000 pounds per hour (900 cases, 40 pounds per case, 
rendered in 6 hours) . To operate with these, a suitable drier, prefer- 
ably continuous and automatic, must be installed. For this purpose 
a hot-air drier is recommended, one designed to utilize the waste heat 
from the boiler fires, or, more simply, a rotary, direct-heat, cylindri- 
cal drier, heated with petroleum burners. This, in order to keep pace 
with the cooker and press, would be required to have the capacity of 
about 1,800 pounds wet or 900 pounds dry scrap per hour. The lat- 
ter figure is obtained by taking 15 per cent of the weight of the orig- 
inal raw cuttings as its equivalent in dry scrap. In the press the 
moisture of this would be reduced to about 50 per cent. Eequisite 
mechanical conveyors for transporting the raw materials from the 
storage bin to the cooker and from one machine to another would 
make the entire operation automatic and would reduce the labor 
required to a minimum. 
Another form of apparatus for small-unit rendering plants is the 
one-operation apparatus, referred to in a foregoing paragraph, which 
prescribes the cooking of the material to be rendered in a closed 
retort, under pressure of steam and with revolving knives or macera- 
tors, the withdrawal of the water and oil which rises to the surface, 
and the evaporation to dryness, under vacuum, of the solids remain- 
ing. Heat for both cooking and desiccation is supplied b} T steam. 
As the entire operation is performed in a closed vessel and as all gases 
and liquids are conducted out of the building in pipes, the process is 
inodorous. While it is automatic it is discontinuous. Low initial 
