AQUATIC PEODUCTS IN ARTS AND INDUSTRIES. 241 



Cera of salmon yields such a small quantity of oil that usually it is 

 not profitable to attempt its extraction. 



In the United States the heads of halibut have been generally util- 

 ized for oil-manufacture since 1870. They are of no value as food 

 and are discarded in dressing the fish for market. In Gloucester and 

 Boston, the headquarters of the halibut fishery, the}' are collected by 

 the oil-manufacturers, cooked, and pressed in the same manner as 

 other waste products. They are placed in large receptacles and 

 treated with steam until the tissues are thoroughly disintegrated, 

 when the oil and water are extracted by subjecting the mass to 

 hydraulic pressure, 1,000 pounds yielding about 20 gallons of oil. 

 The annual product in Boston and Gloucester is about 12,000 gallons, 

 valued at about 30 cents per gallon. When refined by treating with 

 caustic potash, refrigerated, pressed, and sun-bleached, it looks as fine 

 as choice whale oil and is commonly sold as a substitute therefor and 

 at about the same price. 



Sword-fish heads are usually very fat, a single head sometimes yield- 

 ing one gallon of oil. As a rule, however, 100 heads yield about 65 

 gallons of oil. It is extracted in precisel}'' the same manner as in case 

 of halibut-head oil. The quantity prepared is small, probably not 

 exceeding 1,000 gallons annually on the entire New England coast. 

 It is clear and sweet and is probably sold as whale or cod oil. 



The heads of other food-fish as a rule contain little oil. Cod and 

 related species, for instance, contain practically none, and in utilizing 

 them for fertilizer in this country, as well as in the British provinces 

 and in Norway, no effort whatever is made to secure oil therefrom. 



OIL FROM VISCERA OF FISH. 



The quantity of viscera resulting from dressing food-fish at the 

 markets, canneries, drying establishments, and the like in the United 

 States amounts to upward of 100,000 tons annually. In certain 

 species of fishes this material is very oleiferous, yielding as high as 

 150 gallons to the ton; but in most species the viscera are so poor in 

 oil as to preclude their use for this purpose, the possible yield in some 

 instances being as low as 4 or 5 gallons to the ton of crude material. 



Probably the greatest yield of oil is from the viscera of the blue-fin 

 white-fish and the chub or deep-water herring of Lake Michigan. The 

 quantity ranges from 7 to 16 gallons of oil to the barrel and is much 

 greater in winter than in summer. The average quantitj' of oil from 

 the waste of lake trout is about 4 gallons to the barrel of 200 pounds. 

 The yield from herring is small, probablj'^ not exceeding 1 gallon per 

 barrel. The total quantity of oil contained in the viscera of all food- 

 fish taken in the United States amounts probably to upward of 800,000 

 gallons. Only a relatively small proportion of this oil is saved. 



Very few establishments exist in this countr^^ for utilizing the oil 

 contained in the viscera of fish. A majority of these are on the shores 



F. C. 1902 16 



