I82 MADRAS FISHERIES BULLETIN VOL. XIII, 



a fertiliser, while the oil is secondary and is removed partly because 

 of its intrinsic value, partly because its presence in the fertilizer is 

 not only not required but is even inimical, partly because it has no 

 manurial value and tends to clog the soil and delay the decompo- 

 sition of the manure, partly because fertilizer containing much oil 

 is apt to heat to the point of spontaneous combustion. Since it is 

 obtained wholly from the sea it is purely an addition to the produc- 

 tivity of the soil ; it is not merely a transfer as in the case of cattle 

 manure, oil cakes, etc., from the soil to plants and animals and then 

 — and only to some extent — a retransfer to the soil, but an absolute 

 and valuable augmentation of fertilizing constituents; hence its 

 importance to India and a strong reason for its retention within 

 our own borders. Its quantity and value will therefore now be 

 discussed. 



75. Quantity. — As stated in paragraph 28 the weight of dry 

 guano in United States of America practice is nearly 22 per cent of 

 that of the fresh fish, or rather more than I ton per 5 tons; on the 

 Madras West Coast the percentage is as nearly as possible 20 

 per cent. The difference is probably due to the factor of moisture. 

 In the United States of America " dried scrap " in its commercial 

 acceptation, refers to guano containing not more than " 12 per cent 

 of moisture " (Stevenson), but the same authority states that " i^ 

 is not always that so large a quantity of water is eliminated and 

 sometimes the finished scrap contains 25 and even 35 per cent of 

 moisture," chiefly when it is to be used in close proximity to the 

 factories. Probably, however, in fully dried " scrap " the moisture 

 in the stuff, as it leaves the drier, " does not exceed 8 per cent ; " it 

 is the averaging of thoroughly dried and only partly dried scrap, as 

 noted in the preceding sentence, that gives the higher average of 

 moisture connoted by a 22 per cent yield. In giving the average 

 of 10 years ending 1898, the yield of guano per 1,000 fish (666 lb.) 

 is given as " 138 pounds of scrap containing 10 per cent of 

 moisture " ; this is equal to 207 per cent on the fresh fish. Seeing 

 that Tanur guano only contains 8 per cent moisture it is not sur- 

 prising that the dry yield is only about 20 per cent and not 22 as 

 mentioned for the United States of America. The fish guano from 

 Tanur sent to England (Imperial Institute) for analysis, showed 

 only an average of 8*4 per cent, though the samples were sent 

 in an ordinary parcel and must have absorbed moisture since they 

 were despatched in the moist season and reached England during 



