UTILIZATION OF THE FISH WASTE OF THE PACIFIC OCEAN. 41 
not essential. However, even with the continuous cooker a certain 
degree of pressure can be maintained, if desired, by the correct modi- 
fication of the cooker. 
The press in use in the menhaden factories has been designed for 
expressing the cooked menhaden. As that material is markedly 
different from salmon waste, there is no reason to suppose that the 
press efficacious with the former will be so with the latter. How- 
ever, there is every reason to believe that the press so useful with 
the one can be modified so that it can meet the demands of the other. 
This is not a necessary conclusion, since the limits of usefulness of 
this form of press may lie between the requirements of menhaden 
on the one hand and of salmon cuttings on the other. As indicated 
above, this is not believed to be the case. In this connection it should 
be emphasized that, in view of the fact that the screw press has 
never received a thorough demonstration in the salmon-scrap in- 
dustry, before other plants are equipped with it it should be made 
to conform to the demands of that industry. This can be done only 
by thorough experimentation by those familiar with the press and 
the nature of the material to be pressed. 
The rotary, direct-heat drier probably should be the most economical 
type at present available. Its present methods of operation can not 
be so considered. In construction, it is a sheet-iron c} T linder, about 
40 feet in length and 5 feet 6 inches in diameter. It is mounted, at a 
slight angle out of the horizontal, on roller bearings which support its 
weight and on which it revolves. The material to be dried is fed into 
the upper end and falls out at the lower. Also into the higher end is 
blown a stream of hot gases, generated by forcing air from a blower 
through the firebox of a furnace. The wet scrap falls directly into 
this stream of hot gases and by it is assisted through the drier. It 
also is lifted and let fall repeatedly by the rotation of the cylinder. 
Such a drier yields about 45 tons of dr}^ scrap per day. In prac- 
tice the moisture content of the material (fish-pomace) is reduced 
from 55 or 60 per cent to 7 per cent, at a closely estimated cost of 
50 cents per dry ton. This cost is based on the f ollow T ing items : To 
heat the drier, approximately 3} tons of soft coal is required, w T hile an 
additional 1J tons is consumed in supptying the power for the rota- 
tion of the drier and the operation of the conveyors. One skilled 
laborer is required to operate the drier and two unskilled laborers 
to tend the drier furnace and the boilers. 
For the most efficient utilization of a stream of drying gases, 
theory demands that it shall flow from the opposite direction over 
and through the stream of material being dried. Thus the hottest and 
driest gases are brought into contact with the hottest and driest part 
of the material being dried, and the coolest and wettest gases with the 
