The Third Part of the Prosperity of Germany

Prosperity of Germany

so that it is rather preserved intact, until the vault or its covering, constructed from lime, ash, and manure, has been perfectly dried. This having been done, the aforementioned prepared lime must be applied anew to the thickness of a hand's breadth to the previous vault, and you will observe that the humidity of this later mass or second vault is quickly attracted by the first, and this second layer itself is dried. Even after this is finished, a third application must be made from the prepared material in the prescribed manner. And this operation must be repeated so long and often, until the vault has acquired the thickness of one or two feet. When it has this, it is strong enough and no longer needs its wooden support, to which fire can therefore now be applied so that it may be burned away. And thus you have prepared the most suitable instrument for the production of saltpeter in quantity. If the opportunity and the condition of the location permit, it is better to construct three or four vaults in the stated manner, even if of smaller size and capacity, placed next to one another, for they are more convenient for the operation, which any of the practitioners will be able to gather most easily.

It is also better to construct this chamber, which we have called a vault, long and narrow, rather than short and wide, because the fire of such a long chamber, being placed under one part, diffuses its heat optimally to all places, and thus keeps the chamber constantly warm.