No. 3 (1921) MANUFACTURE OF FISH OIL AND GUANO I63 



35. When the oil has been practically freed from visible water, 

 it is usual to "cook " it, or rather to raise it to about 215° F., so as 

 not only to sterilize it but to drive off any suspended water. The 

 oil so heated does not perceptibly darken in colour when steam is 

 used for the heating, while the oil becomes clear by the absence of 

 water and suspended impurities. From the cooking tank the clear 

 oil is drawn off into storage tanks. 



36. The foul water from the separators is sometimes run into 

 " catch-all" tanks, since a quantity of suspended oil and impurities 

 is carried over with the water, and this is caught in the tanks. 

 But in sub-tropical areas, this effluent water is so putrescible from 

 its contents of organic matter that, especially in hot weather, it 

 cannot be thus treated, and is simply run off into the sea. 



37. Quantity.— K?. mentioned above (paragraph 8) this differs 

 enormously according to locality, year, and season ; it is stated 

 that the yield may be as low as I pint (less than one pound) per 

 1,000 fish (666 lb.), and may be as much as and occasionally above 

 15 U.S.A. gallons (lIO lb.) or nearly 17 per cent. Taking the 

 whole Atlantic coast for 20 years, the average of localities and 

 seasons is stated as 43 U.S.A. gallons or 3i'5 lb. or just over 

 5 per cent. But the yield differed greatly in different years; e.g., 

 in several years the aggregate yield averaged 6*84, 6"8l, and 6*38 

 gallons, while in other years the average was 262, 2*79 gallons, etc. 

 Similarly in given stations the amounts differed largely from year 

 to year ; e.g., 6 gallons in one year and 2 gallons in the next. As 

 for locality it is stated that, as might be expected, the fish of 

 northern waters are much fatter than those of warmer southern 

 water; e.g., the yield of the north Atlantic States might be 576 to 

 6'39 gallons, and those of the southern 3'5i. In 1912 the average 

 of the northernmost States was about li'55 gallons, while Virginia 

 and North Carolina gave only 372 and I'98 respectively. Curiously 

 enough the fish seem almost to have deserted the Maine coast 

 (northernmost State) since 1898. 



As for season, it seems that the yield is much higher in autumn 

 than in spring ; presumably the fish, as on the Madras coasts, are 

 fat with high, summer feeding, and store this as fat against the 

 winter; during the winter this is self-consumed, so that in early 

 spring the yield of oil may be I pint per 1,000 fish as against 

 several gallons for the same locality as the average for the same 

 year. It is reported that in one bay the food one year was so 

 3 



