222 



Composition and Value of Guano. 



calculation, however, that the sulphuric acid is of some value as 

 manure, and that the whole cost should not be thrown upon the 

 ammonia. In a ton of sulphate of ammonia there are 1075 lbs. of 

 sulphuric acid, which would be supplied by about 20f cwts. of 

 gypsum, at a cost of 16s. l^d. If, therefore, 



£. 5. d. 



From the cost of 1 ton of sulphate of ammonia .12 0 0 

 Is deducted the agricultural value of its sulphuric acid 0 16 1^ 



11 3 10£ 



will be the expense of the ammonia, or rather more than 5jc7. 

 per lb. 



From the preceding- calculations it will be evident that we shall 

 not greatly err in fixing 6d. per lb. as the value of ammonia, as 

 supplied by the sulphate at its present price of 12/. a ton. 



Muriate of ammonia contains, when quite pure and dry, 31*6 

 per cent, of ammonia. I am unable to say what quantity of 

 water and impurity it may usually contain in its crude state, but 

 it may be sufficiently near for the present purpose to estimate 

 this at 10 per cent. : accordingly, crude commercial muriate of 

 ammonia will have about 28 per cent, of ammonia. 



Taking its average value to be 19/. a ton, and, without any 

 allowance in this case for the acid, the price of ammonia in the 

 muriate will be 7\d. per lb. At 17/. a ton the ammonia would 

 cost about 6Jd ; and at 21/., rather more than 8d. per lb. 



It remains now to inquire what is the cost of ammonia in its 

 other available sources. The importation of oilcake into a farm 

 must be looked upon as an indirect importation of ammonia. In 

 feeding his stock with oilcake the farmer increases the quantity, 

 and, in a greater proportion, the quality of his manures ; and every 

 ton of cake thus consumed is equivalent to the purchase of a 

 certain quantity of ammoniacal manures. 



What relation in value the manure so produced (or imported) 

 may bear to the cost of its importation it is not the purpose of 

 this paper to inquire, nor is the question to be very readily settled. 

 The value of a ton of oilcake regarded as manure is obviously 

 dependent upon the proportion of its original cost, which may be 

 fairly placed to the account of profit in feeding with it. 



Leaving the discussion of this subject to a more fitting place, 

 we may simply calculate the value of ammonia as supplied by 

 oilcake, considered only in a manurial point of view. The market 

 price of oilcake is so variable, that no actual sum can be fixed 

 upon as its average cost; we shall therefore make a calculation 

 for the extreme of fluctuation. 



From the analyses of a great many specimens examined in my 

 laboratory, I find that the average proportion of nitrogen in oil- 



