20 BULLETIN OF THE BUSSEY INSTITUTION. 
practice greatly to be deprecated, I have preferred to retain this 
figure in order to avoid the semblance of unfairness to any manufac- 
turer, and in deference to the estimates previously published by 
chemists. It is possible, of course, that the nitrogenous materials in 
the superphosphates analyzed may not have been derived from fish- 
scrap, but from bone or from flesh or from tankings; and it may 
be that the nitrogen in these materials is more active as a fertilizer 
than that in fish-scrap. Moreover, the price ($15 per ton) at which 
fish-scrap is obtainable upon the sea-board of New England is probably 
much lower than it would be in the interior. Where water-carriage | 
is not to be had, the cost of transporting this rather offensive sub- 
stance would doubtless be comparatively high. 
Both the analyses and the tabular estimates above given accord 
closely with the experience of other chemists, notably with that of 
Professor S. W. Johnson 6f New Haven, who has analyzed a large 
number of fertilizers during the last ten or twelve years at the insti- 
gation of the State Agricultural Society of Connecticut.* They differ, 
on the other hand, to a certain extent, from the statements of various 
manufacturers of superphosphates and of their agents and analysts, 
who allow a certain value ‘per pound intermediate between $0.06 (the 
value of insoluble phosphoric acid) and $ 0.1625 (the value of soluble 
phosphoric acid), for whatever amount of phosphoric acid in the condi- 
tion of the so-called reduced phosphate (2 CaO, H,O, P,O,) a sample of 
superphosphate may contain. In favor of such allowance it is urged that 
the “reduced phosphate,” though scarcely at all soluble in cold water, 
is nevertheless a little soluble in that liquid and more soluble in the 
acid and saline liquids of the soil than the original rock phosphate 
from which the superphosphate has been prepared. 
I deem the practice of making such allowance wrong, for the reason 
that the purpose of a superphosphate is to supply soluble phosphoric 
acid to the land. From what is known of the manner in which the 
soluble phosphoric acid of a superphosphate is distributed and decom- 
posed in the soil, it seems plain that this substance had much better 
be applied by itself without any admixture of phosphates which are 
* See the Connecticut Agricultural Reports for 1858, 1869, and 1870. Compare 
the work entitled “ American Manures,” by W. H. Bruckner and J. B. Chynoweth. 
Philadelphia. 1872. 
