350 BULLETIN OF THE BUSSEY INSTITUTION. 
occurs in the compost-heap as a preliminary step or preparation 
for nitrification proper, was clearly perceived by several of the 
earlier chemists at a time when the question of saltpetre-making 
was much discussed. Many references to the subject will be 
found in the essays on saltpetre-making that are contained in the 
11th volume of the ‘‘ Mémoires des Savans Etrangérs.” Lorgna 
in particular (p. 174 of part I. and pp. 248, 249 of part II.),— in 
arguing that it might be possible to make nitre-beds succeed in the 
open air, especially during the first periods of the fermentation, 
and that the earth need not be put under cover until the time of 
the actual formation of nitre,— proposed to set aside a field having 
light, friable soil shaded by trees; to manure it and sow upon it 
seeds of various plants. When the plants had grown so that they 
were full of sap they were to be spaded under — just after rain, in 
order that they might putrify the more readily ; and the operations 
of sowing seeds and spading under plants were several times re- 
peated. Finally, when the soil was thoroughly impregnated with 
putrified vegetable matter, it was to be put under sheds; since, as 
was urged, it is during the last term of the process of fermentation 
that a nitre-bed stands in greatest need of being protected from 
the weather. 
The mixing of wood-ashes with the earth of nitre-beds was an act 
of a different order from the use of ashes in compost-heaps. It 
depended primarily no doubt upon the power of the carbonate of 
potash in the ashes to react on nitrate of lime in the nitrous earth, 
with precipitation of carbonate of lime and formation of true salt- 
petre. It is not probable that the ashes did much if any good by 
promoting the decay of refractory organic matter in this case as they 
would do in an agricultural compost-heap ; but by virtue of their 
alkalinity the ashes must sometimes have favored nitrification proper 
in the nitre-beds, as they doubtless often do in fields to which they 
have been applied as a fertilizer. Boussingault has insisted on 
this point, and Schloesing and Muntz have shown that nitrification 
is rapid in presence of extremely weak solutions of the carbonates 
of potash and soda, although stronger solutions of these alkalies 
may hinder or even completely stop the action of the nitric ferment. | 
Ordinarily, however, the alkalinity necessary for the nitre-beds was 
obtained by adding to them leached ashes or chalk, and it may 
be true that, in so far as mere nitrification is concerned, carbonate 
of lime (leached ashes) may do just as much or possibly more good 
than carbonate of potash (such as live ashes afford) ; for the solu- 
