Artificial Manures for Swedes. 
107 
position, only gave 10 tons 8 lbs., whilst the produce of the dis- 
solved coprolites amounted to 1 1 tons 12 cwts. 
Dissolved coprolites, which follow guano in the above list, 
virtually produced as great a crop as guano, for the difference of 
56 lbs. is not worthy of consideration. Whenever coprolites 
therefore can be had at a cheap rate, they may be employed as a 
substitute for bone-dust, provided care is taken to dissolve them 
properly in sulphuric acid and to mix them with some nitro- 
genized organic manure. 
The nut-refuse gave as nearly as possible the same produce 
as the mixture in experimental plot No. X., and commercial 
night-soil follows next in the list. A comparison of the crop 
yielded by bone-dust with that yielded by bone-dust dis- 
solved in sulphuric acid, will forcibly exhibit the advantages of 
applying bones in the latter form ; for whilst an equal money 
value of bone-dust only gave an increase of 3 tons 12 cwts., dis- 
solved bone-dust gave an increase of 8 tons 8 cwts. 16 lbs. ; or 
whilst 1 ton of increase raised with the agency of superphos- 
phate only cost 4^. 9ff., 1 ton of increase raised with bone-dust 
implied an expenditure of 11 v. l^d. The form in which an 
artificial manure is applied to the land thus greatly influences 
its action. 
On the whole, we may learn from these experiments that the 
value of different artificial manures for a crop of swedes, and no 
doubt also for other root-crops, principally depends on the 
amount of phosphoric acid contained in them in a form in which 
it can be readily assimilated by the plants. In bone-dust there 
is much phosphoric acid ; but when it is used in an unprepared 
state, in which it still contains all the fat naturally present in 
fresh bones, it often remains in the soil for a very long time 
without readily undergoing decomposition, or that preparation so 
necessary to bring out its full fertilizing effect. All the experi- 
ments confirm the general conclusion which has just been 
expressed ; but more especially the experiment with the economic 
manure, in which the absence of phosphoric acid was proved by 
analysis, shows the necessity of applying to root-crops a fertilizer 
containing a good deal of phosphoric acid. Whatever else the 
virtues of the economical manure may be, it certainly proved the 
least economical dressing of all, as it produced only 6 tons 16 lbs. 
of swedes per acre, or only 16 cwts. 16 lbs. more than the 
unmanured portion of the experimental field. 
In conclusion I will observe that I have carefully determined 
the chemical composition of the roots of each experimental plot, 
in so far at least as it appeared desirable in order to form some 
idea as to the nutritive value of the swedes raised with different 
manuring matters. 
