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 cylinder, 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 dry 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 following items : To 

 heat the drier, approximately 3|- tons of soft coal is required, while an 

 additional 1^ tons is consumed in supplying 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 



