complete knowledge of the method of making all underground works.
Lastly, there are the various systems of assaying5 substances and of
preparing them for smelting; and here again there are many altogether
diverse methods. For there is one method for gold and silver, another
for copper, another for quicksilver, another for iron, another for lead, and
" Stone is a dry and hard mineral body which may either be softened by remaining
" for a long time in water and be reduced to powder by a fierce fire ; or else it does not
" soften with water but the heat of a great fire liquefies it. To the first species belong
" those stones which have been solidified by heat, to the second those solidified (literally
" 'congealed') by cold. These two species of stones are constituted from their own material.
" However, writers on natural subjects who take into consideration the quantity and quality
" of stones and their value, divide them into four classes. The first of these has no name of
" its own but is called in common parlance 'stone' : to this class belong loadstone, jasper (or
" bloodstone) and Aetites (géodes ?). The second class comprises hard stones, either pellucid
" or ornamental, with very beautiful and varied colours which sparkle marvellously ; they
" are called gems. The third comprises stones which are only brilliant after they have been
" polished, and are usually called marble. The fourth are called rocks ; they are found in
" quarries, from which they are hewn out for use in building, and they are cut into various
" shapes. None of the rocks show colour or take a polish. Few of the stones sparkle ; fewer
" still are transparent. Marble is sometimes only distinguishable from opaque gems by its
" volume ; rock is always distinguishable from stones properly so-called by its volume. Both
" the stones and the gems are usually to be found in veins and veinlets which traverse the
" rocks and marble. These four classes, as I have already stated, are divided into many
" species, which I will explain in their proper place."
" Metal is a mineral body, by nature either liquid or somewhat hard. The latter may
" be melted by the heat of the fire, but when it has cooled down again and lost all heat, it
" becomes hard again and resumes its proper form. In this respect it differs from the
" stone which melts in the fire, for although the latter regain its hardness, yet it loses
" its pristine form and properties. Traditionally there are six different kinds of metals,
" namely gold, silver, copper, iron, tin and lead. There are really others, for quicksilver is a
" metal, although the Alchemists disagree with us on this subject, and bismuth is also. The
" ancient Greek writers seem to have been ignorant of bismuth, wherefore Ammonius rightly
" states that there are many species of metals, animals, and plants which are unknown to us.
" Stibium when smelted in the crucible and refined has as much right to be regarded as a
" proper metal as is accorded to lead by writers. If when smelted, a certain portion be
" added to tin, a bookseller's alloy is produced from which the type is made that is used by
" those who print books on paper. Each metal has its own form which it preserves when
" separated from those metals which were mixed with it. Therefore neither electrum nor
" Stannum is of itself a real metal, but rather an alloy of two metals. Electrum is an alloy
" of gold and silver, Stannum of lead and silver (see note 33 ρ 473). And yet-if silver be
" parted from the electrum, then gold remains and not electrum ; if silver be taken away
" from Stannum, then lead remains and not Stannum. Whether brass, however, is found as
" a native metal or not, cannot be ascertained with any surety. We only know of the
" artificial brass, which consists of copper tinted with the colour of the mineral calamine.
" And yet if any should be dug up, it would be a proper metal. Black and white copper
" seem to be different from the red kind. Metal, therefore, is by nature either solid, as I
" have stated, or fluid, as in the unique case of quicksilver. But enough now concerning the
" simple kinds."
'* I will now speak of the compounds which are composed of the simple minerals
" cemented together by nature, and under the word ' compound ' I now discuss those
" mineral bodies which consist of two or three simple minerals. They are likewise mineral
" substances, but so thoroughly mixed and alloyed that even in the smallest part there is
" not wanting any substance that is contained in the whole. Only by the force of the fire
" is it possible to separate one of the simple mineral substances from another ; either the
" third from the other two, or two from the third, if there were three in the same compound.
" These two, three or more bodies are so completely mixed into one new species that the
" pristine form of none of these is recognisable."
" The ' mixed ' minerals, which are composed of those same simple minerals, differ
" from the ' compounds,' in that the simple minerals each preserves its own form so that
" they can be separated one from the other not only by fire but sometimes by water and
" sometimes by hand. As these two classes differ so greatly from one another I usually use
" two different words in order to distinguish one from the other. I am well aware that
