SALTPETER PLANTATIONS 83 
considerable organic material in a partly decomposed condition 
that aids in forming a permanent humus. The texture of the soil 
is improved by this so that the final result is a soil superior to that 
containing only mineral fertilizers. The soil thus treated becomes 
more tenacious, richer, less likely to harden and crack in dry 
weather, washes less with rains and is generally to be preferred. 
Mineral fertilizers may sometimes be mixed to advantage with 
manure. 
SALTPETER PLANTATIONS 
These nitrifying forces are not confined to the soil, but may 
occur in other localities, always resulting in the production of 
nitrates. Before the discovery of the nitrate beds of South Amer- 
ica it was the custom of agriculturists to prepare their own nitrates 
by a simple process, not then understood, but now known to be 
due to nitrifying bacteria. The places where nitrates were thus 
formed were called salipeter plantations, and the saltpeter was pro- 
duced by exactly the processes we have already considered. The 
method was as follows: 
Masses of chalky soil were mixed with various organic bodies 
and the whole heaped into a pyramidal pile, rendered somewhat 
porous by the admixture of brushwood. The heap was still fur- 
ther furnished with fermentable nitrogen by frequently watering 
it with liquid manure. In this heap occurred the various kinds of 
nitrogen decomposition already mentioned, and later the nitrifica- 
tion process began. The result was that nitrates were formed in 
the interior of the heap in large quantity. Eventually the nitrates 
were extracted by water and converted into nitrate of potassium 
by the addition of some potassium salt. 
This method of making saltpeter was discovered before science 
had any idea of the real nature of the process, and it was a practical 
means of utilizing a part of the nitrogen in the organic substances 
derived from animals and plants. Whether it was the most eff- 
