18 On the Valuation of Unexhausted Manures. 
account accumulations within the soil which, if not taken up, 
would be liable to loss bj drainage. 
When superphosphate has been applied to roots, and no crop 
has been taken from the manure produced by their consumption, 
for 20a'. of its cost may be allowed if the roots be consumed 
on the land, or 8s. if in the yards ; or if corn have followed the 
roots, the grain sold and the straw left, 2s. may be allowed. 
When superphosphate has been applied for a corn-crop, the 
corn sold and the straw left, compensation to the extent of 5s. for 
20s. cost of the manure might be granted. 
If superphosphate have been applied to grass-land which has 
been grazed, for every 20s. cost, 12s. after one year, 4s. after two, 
but nothing after three years should be allowed. If applied to 
grass-land, and hay have been taken and consumed, 10s. after 
one year, 2s. after two years, and nothing after three years. If 
hav have been sold, nothing should be claimed. 
No compensation should be claimed for the unexhausted residue 
of superphosphate, whenever a second crop of any kind has been 
taken since the application, excepting corn after roots, grass 
grazed, or hay consumed, as above specified. 
8. Guano, in its Natural State, or Manufactured. 
Under the existing conditions of the Peruvian guano trade it 
is impossible to speak with any certainty, even as to the value 
of guano as a direct manure. It must therefore be more difficult 
still to speak definitely as to the value of the residue it may 
leave in the soil after the removal of a crop. 
At one time the farmer could calculate upon receiving guano 
containing nitrogen equal to 16 per cent, of ammonia ; more 
recently he had to be satisfied with 14 per cent. ; and more 
recently still, not only a lower average per cent, than this, but 
great uncertainty whether he would receive that amount, half as 
much, or even less. v 
The present agents for the sale of Peruvian guano in this 
country have, however, quite recently informed me, that, during 
the time the agency has been in their hands, their importations 
have averaged nearer 13 than 12 per cent, of ammonia, and that 
cargoes analysing anything below 12 per cent, have been quite 
the exception. Such guano, in its natural state, will probably 
also contain from 25 to 30 per cent, of phosphates. But some 
they mix with sulphuric acid, and manufacture it into a sub- 
stance of uniform quality containing nitrogen equal to about 
10 per cent, of ammonia, superphosphate equal to about 20 per 
cent, of phosphate rendered soluble, and only about 4 per cent. 
<jf phosphates left undissolved. 
