A few years since some have made their crucibles, and other vessels that will endure the fire well, of earth brought out of _England_, and _France_ into _Holland_, which have retained metals very well in the fire, but not salts, because they are too porous and not so compact as those of _Hassia_, wherefore those of _Hassia_ are still preferred before others, retaining better, metals, and salts. But although this earth be brought from thence to other places, yet such strong crucibles could not be made thereof, the cause whereof being not the constitution of the air, and place to Which some have falsely imputed it, but an error in the making and burning of them. For in _Hassia_ there is a great abundance of wood, of which there is no sparing in the burning the crucibles even to a stony hardness, which could not be done by a smal Fire of turffes. The like errour is committed about stone pots, and other vessels which are made at _Frechemium_ and _Siburgus_, and other places near _Colen_, which are carryed almost through all Europe, the goodness whereof is ascribed only to the earth, and not to the making. But now experience hath taught us that any good earth doth become stony in a violent fire, without respect of the place where it is taken. Wherefore it is very probable, being a thing possible, that such vessels are made elsewhere: for every earth being burnt retaining a white colour, _viz._ with an indifferent Fire, makes pots, and crucibles porous, but with a stronger, and with a longer delay, compact like glass, especially if common salt be cast in a plentiful manner upon them, being burnt with a very strong fire, because it addes to them being very well burnt within an external glasy smoothness, by which means they will be the better able to retain spirits in the Fire. Wherefore let no man doubt concerning the making the foresaid vessels of any other earth that is white in burning, with the help of a very strong Fire: which by how much the greater whiteness it gets in burning, by so much the better and excellent pots it makes; and seeing there is a great difference of making crucibles to be set in the Fire, and of stone pots retaining liquid things, I shall shew the manner of making both, _viz._ of stone pots belonging to the first and second furnace, and of crucibles to the fourth, and thus it is. He that will try the goodness of white and pure earth, _viz._ whether it grows stony in the fire, let him cast a peice of crude earth of the bigness of a hens egge into a very strong Fire, observing whether it doth quickly or slowly cleave and break in pieces; which if it doth not cleave and become powder, although it may have some cracks, is good earth, and fit for burning, if so be the mixture be well made, in which lys the art.