548 
Value of Artificial Manures. 
siderable a proportion of phosphoric acid readily soluble in 
water. Guano, in fact, in addition to the large quantity of 
nitrogen it furnishes, is of the nature of superphosphate of lime. 
I have found that the phosphatic varieties of guano also contain 
soluble phosphates ; and hence, no doubt, their immediate action 
as turnip manures. 
With the average composition of guano before us, it may be 
worth while to calculate what would be its cost if the various 
ingredients were supplied from other sources. Taking its actual 
price, we shall then be in a position to ascertain at what cost they 
are really bought in this manure. 
Ammonia 16^ tons, at 68l. per ton (its cost in\ 
sulphate) I i 1,1 22- 
Organic Matter 52 tons, at 1/. per ton 52. 
Potash* 3 J ,, at 31/. 108 
Insoluble Phosphate of Lime 23 at7/. ,, 161 
Soluble Phosphate . . . . 7 , , at 32/. , , 224 
£1,667 
or about 16/. 10s. per ton. 
Now, as the importer's price for Peruvian guano is 11/. per 
ton, it is obvious that all the ingredients will be bought at as 
nearly as possible two-thirds of the prices named ; hence the 
prices which I have given in the Table for phosphate of lime and 
ammonia, as supplied by Peruvian guano. 
If, however, it appears clear that guano is a cheap manure, even 
at the high price which it has now reached, it must be remem- 
bered that its use is attended with the disadvantage that, as a 
compound manure, the purchaser may obtain what he does not 
require. In sulphate of ammonia he buys ammonia only, and in 
mineral superphosphate, and in sulphate of potash, he may obtain 
either of the ingredients which he wants precisely as he requires 
them. In guano he has no choice, but must take the mixture as 
he finds it. It would, therefore, be a mistake to endeavour to 
put upon the ingredients of guano the price which they bear in 
other forms, a circumstance which the importers will do well to 
consider. 
I now proceed to tabulate the analyses of a number of samples 
of superphosphate of lime, which have been received in the labo- 
ratory since the year 1852. I shall not attempt to group them 
in any relation to their composition, but shall present them as a 
faithful record of the very varying character of this manure as 
met with in the market. I should observe that many of the 
samples have been sent to me by manure dealers, and may^ 
therefore, be taken to represent their immature attempts in the 
manufacture of this manure. 
* The percentage of potash is taken from my early analyses. We are not in 
the habit of determining the proportion of this ingredient of guano, and the- 
quantity is therefore not given in the preceding analyses. 
