Page:Popular Science Monthly Volume 45.djvu/79

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the drying field comprises nearly twenty acres. From first to last the greatest care is taken that no foreign substance shall become mixed with it. When it is sufficiently dry it is bagged for transportation, either to the manufacturer of artificial fertilizers or direct to the farmer. The total quantity of menhaden "scrap" manufactured during the nineteen years from 1874 to 1892 inclusive was 912,467 tons (dry and acid), and the amount made from other non-edible fishes and waste fish in the United States is estimated

PSM V45 D079 Non edible fish scrap processing.jpg
Fig. 4.—Interior of Curb Room in Factory, showing the Iron Cylinders in which the Scrap is Pressed.

at 150,000 tons. By analysis, the average percentage of nitrogen was found to be eight per cent in the dry scrap and six per cent in the acid, while the acid guano contained four per cent of phosphoric acid, and the dry seven per cent. This gives us a total plant food (nitrogen and phosphoric acid) of 135,000 tons, or about $31,000,000 worth at the present rate fixed by the New England experiment stations.

The average price at which this fish guano was sold was fifteen dollars per ton for the acid scrap and twenty-five dollars for the dry. The guano from the Peruvian deposits which has been imported into this country during the past thirty years contained from four to eight per cent of nitrogen, with about an equal percentage of phosphoric acid, and millions of dollars have been paid for it at the rate of from forty-five dollars to eighty dollars per ton. Why such a great disproportion exists in the prices seems