AQUATIC PKODUCTS AS FEETILIZERS. 261 



middle, where is stationed a trough or chute with a covering movable 

 in sections of short length. In this trough runs a conveyar, consist- 

 ing of two parallel endless chains, between which, at intervals of 2 or 

 3 feet, are attached pieces of board which act as buckets to push the 

 fish along through the trough when a section of the covering is removed. 

 This trough with endless carrier is in use in practically all the large 

 factories, irrespective of the method of cooking. It carries the fish 

 to the cooking bins, or to the steam cooker in case the latter is 

 employed, traps or slides in the bottom of the trough permitting the 

 distribution of the fish into any of the tanks desired. 



The cooking bins or tanks are large rectangular wooden boxes hav- 

 ing capacity of from 50 to 100 barrels each and arranged with a lattice 

 platform, about 4 inches above the bottom, on which the fish rest. 

 Between the lattice platform and the bottom there is a nest of steam 

 piping connected with a pipe leading from steam boilers. A water 

 pipe also leads into the bin, through which salt water for cooking the 

 fish is pumped into the tanks to a depth of about 1 foot or more. For 

 convenience in handling the materials, the bins are commonlj^ 

 arranged in two adjacent rows, and above them runs the endless car- 

 rier conveying the fish from the receiving bin. On the outer side of 

 each of the two rows of tanks runs a track leading to the presses, to 

 be described later. When the bins are filled with fish, steam is 

 turned into the piping in the bottom and heats the water, thus cook- 

 ing the fish, reducing them to pulp, and breaking the oil cells. The 

 amount of the cooking determines the extent to which the oil is 

 removed. If carried to an extreme point, nearly all the oil can be 

 pressed out. But severe cooking results in greatly damaging the 

 quality of the oil and in loss of a certain amount of the nitrogenous 

 comi)ounds so imj)ortant in determining the commercial value of the 

 scrap. It is, therefore, important that the heat be so regulated as to 

 extract as much oil as practicable without injuring the quality and 

 with a minimum loss of nitrogen. The requisite degree of cooking is 

 reached when the fish crumble to pieces easily. A high degree of 

 temperature is maintained for about fifty minutes, when the mass of 

 fish is broken up and then fiermitted to simmer for four or five hours. 

 The free oil and water are then drawn oft" and the fish j)ermitted to 

 drain for several hours. 



During the last two or three years the largest factories on the coast 

 have been using continuous steam cookers. The most poj)ular form is 

 constructed so that a conveyor transmits the fish into a steam-tight 

 receptacle, into which a large number of jets of steam are introduced, 

 which thoroughlj" cooks the mass. The process is conti nuous, requiring 

 about fifteen minutes for the fish to pass through, and the capacitj^ of 

 each cooker is about 600 barrels per hour. From the cooker the mass 

 of fish is carried by means of a screw conveyor into an upright elevator 

 casing, whence a bucket elevator carries it to receiving tanks, where 

 it drains overnight. These tanks are usually about 10 feet squg^-e 



