cioo Mr. Majfey on Saltpetre. 
good caufe to believe, that a clofe, warm, moift 
•air is the greateft promoter of this procefs; 
and, therefore, muft have leave to think, that 
a vault, or a cellar, muft be the moft proper 
repofitory for thefe materials, where their putre¬ 
faction, being carried on with the greateft vigour, 
muft, of courfe, be the fooner completed. 
Or, in defeCt of thefe conveniences, that the 
fame end might be anfwered by laying them, 
about a yard thick, upon a piece of ground, funk 
a few inches below the level, and bedded with clay, 
where, through the rain that falls, in the fpace 
of a year or two, they muft be completely putre¬ 
fied j particularly, if they were now and then 
turned over, and no frefh additions were made 
to thtm for, whilft we continue to heap frefli 
materials upon old dunghills, it is impoftible 
that the whole mafs fhould be equally putrefied: 
It is obfervable, that the writer laft mentioned 
fays not a word of the ufe of putrefaction, nor 
of the expediency of promoting this procefs, by 
all the means that lie in our power, in order to 
accelerate the maturity of thefe earths; which we 
commonly attribute to hi's ignorance of this 
circumftance. 
Nor does ‘the practice of the faltpetre makers 
indicate any fuperior knowledge. Many of their 
nitre beds ate raifed ten or twelve feet high, 
whofe putrefaClion muft advance very (lowly, 
through the pieflure of the upper parts upon the 
I X*’ lowert 
