540 
Value of Artificial Manures. 
Phosphate of lime again costs from a little more than a half- 
penny to nearly a penny per lb., according to its origin. 
Now, to enable us to come to any estimation of the value of a 
manure, we must adopt some distinct standard, and it will be 
seen that I have taken as the price of ammonia 6d. per lb. When 
guano is bought, the purchaser will obtain it at a cheaper rate ; 
when sulphate of ammonia is the source, at a higher cost. If 
there existed any unlimited supply of ammonia not in mixture 
with other substances, then undoubtedly the price would be 
regulated by that supply. 
Guano contains, as we know, other substances besides am- 
monia, and in fixing the price of the latter all the other in- 
gredients are taken into account. We cannot therefore buy 
ammonia in guano without buying phosphate of lime, potash, 
&c. This circumstance, together with the fact that although the 
importations of guano are enormous the supply is not always 
equal to the demand, prevents us from fixing the cost of ammonia 
upon the basis of guano. 
At the end of this paper I propose to give a great number of 
analyses of guano and superphosphate of lime executed in this 
laboratory since the commencement of the year 1852, and subse- 
quently therefore to my paper on these manures. It will then be 
seen on what grounds I have given for ammonia and soluble 
phosphate of lime, the prices set against them in the Table. 
After all, these two elements of manure are those of the 
greatest importance, and their just valuation is of paramount 
necessity. 
At the end of the Table I have placed the numbers which I 
adopt as averages for the principal ingredients of manure, 
namely, ammonia, phosphate of lime (soluble and insoluble), and 
potash. I have also given the prices to be apportioned to several 
salts, such as sulphate of soda, &c., as these salts are sometimes 
stated in the result of an analysis. There is a seeming discre- 
pancy in the price of these and that mentioned in the previous 
Table, but it will be remembered that the latter refers to the com- 
mercial or impure article, whilst the prices in this table are those 
of the absolute substance. 
In calculating the value of ammonia, potash, &c., as supplied 
bv their sulphates, I have altogether omitted the cost of the 
sulphuric acid, as this substance in the form of sulphate of 
lime is so abundantly met with in soils tliemselves ; and its cost, 
if actually supplied in that form, is so slight as not materially 
to affect that of the otlier ingredient. Thus a ton of sulphate 
of ammonia contains 1194 lbs. of sulphuric acid, which would be 
supplied in a little more than a ton of sulphate of lime, costing 
about 20s., or one-fifteenth of the whole price of the sulphate of 
