I878.J 
Economy of Nitrogen. 
149 
into these compositions is doubtless lost, — certainly in 
the latter case, — but its quantity is not sufficiently large to 
render it worthy of especial attention. Of far more moment 
is the bone-ash wasted in refining argentiferous lead, no less 
than 1 7 lbs. being consumed for every ton of the metal 
operated upon. This is, if we refer to our former standard, 
a quantity nearly sufficient to build up the skeleton of a 
man. We are not aware that the bone-ash thus employed 
in refinery hearths is afterwards collected and purified from 
adherent traces of lead, so as to be fit for agricultural uses. 
Many iron-ores contain phosphorus. Thus in vivianite, 
phosphoric acid maybe present to the extent of 30 percent. 
In a few instances this constituent is separated in an avail- 
able form, but in the majority of cases it remains partly in 
the iron, to the great dissatisfaction of the manufacturer, 
who finds his product much impaired, and partly in the 
slags. Under both these circumstances it is generally 
wasted. 
Phosphoric acid, combined with soda or potash, enters 
into the composition of certain “ dung-substitutes ” used by 
the calico-printer. Here, again, it must be regarded as 
ultimately wasted, since, when its purpose is served, it is 
washed into the sewers along with a variety of substances, 
many of them hostile to vegetable life, and therefore ill- 
fitted for application to the soil. 
But even the phosphoric acid that is supplied to the fields 
in the forms of superphosphate, of bone-dust, Peruvian 
guano, farm-yard manure, night-soil, &c., and is there assi- 
milated by the crops, is still afterwards in great danger of 
being turned aside from its normal channel of circulation, 
and thus of being substantially lost. Everyone in these 
days has learnt that animals, in their excreta,— -solid, liquid, 
and aeriform, — give back all the matter which they have 
assimilated, and which has for a time formed part and 
parcel of their bodies. If the solid and liquid excreta, 
therefore, of all the animals fed upon the produce of a plot 
of land, of say 10 acres in size, together with all the waste 
or residual portions of the crops, are returned to that plot, 
its fertility — i.e., its power of producing grain or vegetables, 
or of feeding cattle — will remain substantially unimpaired. 
But if this is negledted, or done only in part, a gradual 
decline of fertility must take place. We may, indeed, by 
importing bone-ash, Peruvian guano, and the like, keep up 
the needful supply of phosphoric acid in a 10-acre plot, or 
possibly in the whole of England; but this is, in familiar 
phrase, simply “ robbing Peter to pay Paul.” The whole 
