chap. vii.

what iron is, and of what substance, and its uses.

f or that now we have declared the origin and nature of the loadstone, we think it necessary first to add a history of iron and to indicate the hitherto unknown forces of iron, before this our discourse goes on to the explanation of magnetick difficulties and demonstrations, and to deal with the coitions and harmonies of loadstone with iron. iron is by all reckoned in the class of metals, and is a metal livid in colour, very hard, glows red-hot before it melts, being most difficult of fusion, is beaten out under the hammer, and is very resonant. chemists say that if a bed of fixed earthy sulphur be combined with fixed earthy quicksilver, and the two together are neither pure white but of a livid whiteness, if the sulphur prevail, iron is formed. for these stern masters of metals who by many inventions twisting them about, pound, calcine, dissolve, sublime, and precipitate, decide that this metal, both on account of the earthy sulphur and of the earthy mercury, is more truly a son of the earth than any other; they do not even think gold or silver, lead, tin, or copper itself so earthy; for that reason it is not smelted except in the hottest furnaces, with bellows; and when thus fused, on having again grown hard it is not melted again without heavy labour; but its slag with the utmost difficulty. it is the hardest of metals, subduing and breaking all things, by reason of the strong concretion of the more earthy matter. wherefore we shall better understand what iron is, when we shall declare what are the causes and substance of metals, in a different way from those who before our time have considered them. aristotle takes the material of the metals to be vapour. the chemists in chorus pronounce their actual elements to be sulphur and quicksilver. gilgil mauritanus gives it as ashes moistened with water. georgius agricola makes it out to be water and earth mixed; nor, to be sure, is there any difference between his opinion and the position taken by mauritanus. but ours is that metals arise and effloresce at the summits of the earth's globe, being distinguished each by its own form, like some of the other substances dug out of it, and all bodies around us. the earth's globe does not consist of ashes or inert dust. nor is fresh water an element, but a more simple consistency of evaporated fluids of the earth. unctuous bodies, fresh water devoid of properties, quicksilver and sulphur, none of these are principia of metals: these latter, things are the results of a different nature, they are neither constant nor antecedent in the course of the generation of metals. the earth emits various humours, not begotten of water nor of dry earth, nor from mixtures of these, but from the substance of the earth itself: these humours are not distinguished by contrary qualities or substance, nor is the earth a simple substance, as the peripateticks dream. the humours proceed from vapours sublimated from great depths; all waters are extracts and, as it were, exudations from the earth. rightly then in some measure does aristotle make out the matter of metals to be that exhalation which in continuance thickens in the lodes of certain soils: for the vapours are condensed in places which are less hot than the spot whence they issued, and by help of the nature of the soils and mountains, as in a womb, they are at fitting seasons congealed and changed into metals: but it is not they alone which form ores, but they flow into and enter a more solid material, and so form metals. so when this concreted matter has settled down in more temperate beds, it begins to take shape in those tepid places, just as seed in the warm womb, or as the embryo acquires growth: sometimes the vapour conjoins with suitable matter alone: hence some metals are occasionally though rarely dug up native, and come into existence perfect without smelting: but other vapours which are mixed with alien soils require smelting in the way that the ores of all metals are treated, which are rid of all their dross by the force of fires, and being fused flow out metallick, and are separated from earthy impurities but not from the true substance of the earth. but in so far as that it becomes gold, or silver, or copper, or any other of the existing metals, this does not happen from the quantity or proportion of material, nor from any forces of matter, as the chemists fondly imagine; but when the beds and region concur fitly with the material, the metals assume forms from the universal nature by which they are perfected; in the same manner as all the other minerals, plants, and animals whatever: otherwise the species of metals would be vague and undefined, which are even now turned up in such scanty numbers that scarce ten kinds are known. why, however, nature has been so stingy as regards the number of metals, or why there should be as many as are known to man, it is not easy to explain; though the simple-minded and raving astrologers refer the metals each to its own planet. but there is no agreement of the metals with the planets, nor of the planets with the metals, either in numbers or in properties. for what connexion is there of iron with mars? unless it be that from the former numerous instruments, particularly swords and engines of war, are fashioned. what has copper to do with venus? or how does tin, or how does spelter correspond with jupiter? they should rather be dedicated to venus. but this is old wives' talk. vapour is then a remote cause in the generation of the metals; the fluid condensed from vapours is a more proximate one, like the blood and semen in the generation of animals. but those vapours and juices from vapours pass for the most part into bodies and change them into marcasites and are carried into lodes (for we have numerous cases of wood so transmuted), the fitting matrices of bodies, where they are formed as metals. they enter most often into the truer and more homogeneal substance of the globe, and in the process of time a vein of iron results; loadstone is also produced, which is nought else than a noble kind of iron ore: and for this reason, and on account of its substance being singular, alien from all other metals, nature very rarely, if ever, mixes with iron any other metal, while the other metals are very often minutely mixed, and are produced together. now when that vapour or those juices happen to meet, in fitting matrices, with efflorescences deformed from the earth's homogenic substance, and with divers precipitates (the forms working thereto), the remainder of the metals are generated (a specifick nature affecting the properties in that place). for the hidden primordial elements of metals and stones lie concealed in the earth, as those of herbs and plants do in its outer crust. for the soil dug out of a deep well, where would seem to be no suspicion of a conception of seed, when placed on a very high tower, produces, by the incubation of sun and sky, green herbage and unbidden weeds; and those of the kind which grow spontaneously in that region, for each region produces its own herbs and plants, also its own metals.

70here corn exults, and there the grape is glad,

here trees and grass unbidden verdure add.

so mark how tmolus yields his saffrone store,

but ivory is the gift of indian shore;

with incense soft the softer shebans deal;

the stark chalybeans' element is steel:

with acrid castor reek the pontic wares,

epirus wins the palm of elian mares.