AQUATIC PRODUCTS AS FERTILIZERS. 263 



pressing is iiroperly performed. The chum now passes to the scrap 

 room and its further treatment is described on pj). 265-268. 



About two-thirds of the total amount of oil obtained runs from the 

 cooked fish while it drains in the vats, the remaining- one-third being 

 extracted by the presses. The former is a trifle better than the latter, 

 as it is somewhat lighter in color. The two grades are sometimes kept 

 separate, but such is not the general practice. 



Among the many methods of extracting the oil which have been 

 tried but not adopted is the use of fumes of benzine or bisulphide of 

 carbon. When these are lirought'in contact with the fish in air-tight 

 chambers, they absorb the oil, the liquid result collecting in tanks at 

 the bottom of the receptacle and the benzine being subsequently 

 expelled b}^ evai^oration. 



Much attention has been paid to devising a continuous i^rocess of 

 cooking and pressing, in which the elements of labor are reduced to 

 a minimum. When the Stanley process was invented, about five 

 years ago, it was thought that the problem was solved and the patent 

 rights were sold for a very large sum of money. In this i^rocess the 

 fish are cooked in boiling water in a large, comparatively shallow, 

 semicylindrical tank, the lower portion of which is fitted with a worm 

 conveyor, while near the top is a perforated plate or grating, above 

 which the fish or other solid matter can not pass, but through which 

 the water and oil rise. The material is fed in through a hopper at 

 one end and is discharged at the other end, being carried forward by 

 the worm conveyor, which also reduces the material to a finely divided 

 state, thus enabling- the action of the water upon all parts of the 

 material freely to liberate the oil. The oil rises to the surface of the 

 water in the cooking- vessel and escapes through a pipe in the end 

 into a settling tank. From the bottom of this tank whatever water 

 has come over with the oil is pumped back into the cooking vessel, 

 entering at the opposite end from the outlet through which the oil 

 flows and at a point near the surface of the level at which the water 

 in the boiler is constantly kept, thus creating a current which carries 

 the oil constantly forward toward the outlet. The scrap from which 

 the oil has been liberated is carried forward to an outlet in the bottom 

 of the cylinder by the worm conveyor and falls into an upright eleva- 

 tor casing having elevator buckets running upon an endless chain, 

 which carry the material up and over, dumping it into a receptacle 

 suitable for removing for further treatment. The liquid matter is 

 carried up by the elevator buckets, drains through them, and returns 

 to the liquor in the cooking apparatus. This x^rocess, however, has 

 not yet been found suificiently practical for general adoption. 



As long ago as 1858 the Ocean Oil and Guano Companj^ of Southold, 

 N. Y. , used a steam cylinder cooker somewhat similar to the continuous 

 cooker now in use. This is said to have been invented by a French- 

 man named De Molon, and is described in a pamphlet issued by the 

 above company in 1860 as follows: The raw fish, in quantities of If 



