538 
Value of Artificial Manures. 
of each ingredient, by reference to the other sources of supply and 
sharing the advantage or h)ss of the comparison in proper pro- 
portion between the different ingredients. An example will 
best serve to make this plain. 
Let us suppose that a farmer wishes to apply to his soil nitric 
acid in the state of a nitrate, and potash in some form of that 
alkali ; it is obvious that he could most readily do this by means of 
nitrate of potash, but the question arises as to the economy of 
such a proceeding. 
Nitrate of potash containing 90 per cent, of real nitre, we shall 
suppose to cost 40/. per ton, which corrected for pure nitrate would 
be 44Z. 8s. Nitrate of soda containing 95 per cent, real nitrate 
is to be taken at 18Z. lO^t. per ton, which corrected, as in the 
other case, will be 19Z. Now 1 ton of nitrate of Soda contains 
1423 lbs. nitric acid, and as we shall assume that the soda is of 
no agricultural value, those 1423 lbs. of nitric acid will have to 
bear all the cost of the salt. At this rate we shall buy nitric 
acid in nitrate of soda at Sj%d. per lb. 1 ton of nitrate of potash 
contains 1197 lbs. nitric acid and 1043 lbs. of potash : these 1197 
lbs. nitric acid could be supplied in the state of nitrate of soda for 
15Z. 19s., and consequently the diffference between this sum and 
44/. 8s. (the cost of a ton of nitrate of potash) or 28/. 9s., would 
be the cost of the potash alone, or at the rate of Q^d. per lb. 
Now in sulphate of potash, as will be seen by a Table presently 
to be given, potash is bought at about 3jc?. per lb., or just half 
the above price. 
It is obvious, therefore, that in buying nitric acid and potash 
in the form of nitrate of potash we should buy one or both of 
them much too dearly. Indeed, in buying the ingredients of 1 
ton of nitrate of potash separately, in the form of sulphate of 
potash and nitrate of soda we shall have a cost as follows : — 
£. s. 
1197 lbs. of Nitric Acid at S'jti. per lb 15 19 
1043 lbs. of Potash at 3,^. per lb 14 6 
Making the total cost of the two ingredients . . . . 30 5 
Instead of 44/. 8s., Avhich it would be if bought as nitrate of 
potash. 
The proper way in this case is to share the additional cost of 
the last salt pro rata between the two ingredients. In this way 
we find that nit,rate of potash furnishes nitric acid at 4/i,c?., and 
potash at Aj%d. per lb. 
In drawing up a Table to be used in the calculation of the value 
of manures, I propose to give the results in three different ways, 
in order that each person may employ that method which appears 
to him the simplest. 
The following Table gives the cost of all the different sub- 
stances, as calculated by myself: — 
