Jean Rey (c. 1582/3-c. 1645)

On an Enquiry into the Cause wherefore Tin and Lead Increase in Weight on Calcination

excerpt, originally published as a pamphlet in Bazas, France, 1630 [from Alembic Club reprint #11, Essays of Jean Rey (Edinburgh, 1895)]

Preface

Some eminent personages having observed with astonishment that tin and lead increase in weight when they are calcined, have been seized with a praiseworthy desire to enquire into the cause of this phenomenon. It has proved a goodly subject, but the enquiry has been troublesome, and its fruits very small: in so far that after having directed their thoughts to all quarters, they have only been able to adduce reasons so feeble that no man of sound judgment dares trust them for support, or by their aid shelter his mind from all doubt. The sieur Brun, Master Apothecary in Bergerac, having lately paid attention to this augmentation, and believing, as I apprehend, that no one before him had been aware of it, has invited me in one of his letters to enter on this line of thought and furnish him with the cause. Now, since he is a person whose integrity of life, rare experience in his art, and other patent virtues, oblige every honest man to wish him well, I confess that these qualities have had such power over my affections, that I cannot deny him this request. At his prayer, therefore, and friendly solicitation, I have devoted several hours to the question, and conceiving to have hit the mark I produce from them these Essays of mine. Not without foreseeing very clearly that I shall incur at first the accusation of temerity, since in them I run counter to sundry maxims approved for many centuries by the majority of philosophers. But what temerity can there be in exposing the truth to light of day when one has known it? Might I not more justly be reputed childishly fearful if I dared not divulge it, and sordidly envious if I held it concealed? Of the last two accusations I clear myself, hoping to see myself freed of the first by all intelligent persons, who, after having tasted of my reasons, will, if they find them to their liking, be grateful to me for having set them forth: and, if they like them not, will not refrain from praising my efforts to seek the truth in so arduous a question, and will be incited by my example to treat the matter more dextrously, to which I invite them. In any case I shall have testified to the public the desire I have of serving it by letting this paper slip from my hands, although it may be that some hurtful stigma will thereby be graven on my reputation.

[end of preface; Essays 1-15 omitted]

Essay XVI. Formal response to the question, why Tin and Lead increase in weight when they are calcined.

Now I have made the preparations, nay, laid the foundations for my answer to the question of the sieur Brun, which is, that having placed two pounds six ounces of fine English tin in an iron vessel and heated it strongly on an open furnace for the space of six hours with continual agitation and without adding anything to it, he recovered two pounds thirteen ounces of a white calx; which filled him at first with amazement, and with a desire to know whence the seven ounces of surplus had come. And to increase the difficulty, I say that it is necessary to enquire not only whence these seven ounces have come, but besides them what has replaced the loss of weight which occurred necessarily from the increase of volume of the tin on its conversion into calx, and from the loss of the vapours and exhalations which were given off. To this question, then, I respond and sustain proudly, resting on the foundations already laid, "That this increase in weight comes from the air, which in the vessel has been rendered denser, heavier, and in some measure adhesive, by the vehement and long-continued heat of the furnace: which air mixes with the calx (frequent agitation aiding) and becomes attached to its most minute particles: not otherwise than water makes heavier sand which you throw into it and agitate, by moistening it and adhering to the smallest of its grains." I fancy there are many who would have been alarmed by the sole mention of this response if I had given it at the beginning, who will now willingly receive it, being as it were tamed and rendered tractable by the evident truth of the preceding Essays. For those without doubt whose minds were preoccupied with the opinion that air was light, would have rushed to oppose it. Why (they would have said) does not one extract cold from heat, white from black, light from darkness, since so much heaviness is extracted from air, a thing inherently light? And those who chanced to have bestowed their credence on the heaviness of air, would not have been able to persuade themselves that it can ever increase weight, being balanced in itself. On this account I was constrained to show that air had weight; which was recognisable by other means than the balance: and that even with the latter, a portion previously changed and made denser could manifest its weight. All this I have done as briefly as I found possible, and without advancing anything not strictly germane to this matter: to elucidate which at all points it only remains for me to state and refute succinctly some opinions which others have held or might hold; and to resolve the objections which might be made to my answer.

Essay XVII. That it is not the disappearance of the celestial heat giving life to the lead, or the death of the latter, which augments its weight on calcination.

Of all those whom I know to have written on this question, Cardan presents himself first, and asserts in the fifth book de Subtilitate that lead on conversion into cerussa, or on calcination, augments its weight by one-thirteenth, afterwards giving this reason--That the lead dies, inasmuch as the celestial heat, which was its soul, vanishes, its presence having previously given it life and lightness, as its absence gives it death and heaviness. This he confirms by the example of the animals, which death renders heavier by the extinction of this celestial heat, which, according to his belief, is the soul of animals as well as of all other mixed and composite bodies. This opinion has several shortcomings (to say nothing worse). Firstly, because it attributes life to the lead. Secondly, because it maintains that the presence of celestial heat makes the lead light, and its absence heavy. Thirdly, because it gives the same reason for the increase of weight of lead on calcination, and of animals on their death. Nothing of all that is the case. For touching life, how can lead have it, since it is a homogeneous body, without distinction of parts, without organs, and without any vital effect or action? If it moves downwards, so does cerussa, which is only its dead body: if it is cooling, cerussa is cooling also. Then how could it preserve that life in the million forms it can assume and put off, remaining always lead? How in a furnace (and this is a much greater marvel) in which it can be kept molten a day, a month, or even a whole year? It would need a very tenacious soul, to suffer so much without dislodging. Everybody, too, agrees that from death to life there is no return. Yet chemists promise us that if we moisten the calx of lead and mix it with water in which barilla has been dissolved, and having dried it, place it in a crucible which has only a small air-hole open, and expose it to a hot and quick fire, we shall reduce it to its first condition. As regards his notion that the celestial heat makes substances light Scaliger raises the pertinent objection that the celestial sphere which abounds in this heat, being the source of it, must itself be light, and in consequence univocal with the other bodies; which is ridiculous. The loss of this heat, also, cannot render them heavy, for I have proved in what precedes that nothing augments in weight but by addition of matter or by shrinking in volume, of which there is nothing here: for the heat in vanishing can add nothing to the lead, and the volume appears to be visibly augmented, the solid and compact lead being broken down into so many particles that their number borders on the infinite. It would also follow that plants become heavier when they die, their celestial heat being dissipated: but the opposite is evident to all. As to the heaviness which increases in animals on their death, its cause is far removed from that which augments the weight of lead on calcination. As long as the animal lives, its natural heat subtilizes, expands and augments the dimensions of the humours, flesh, and every part of it which is dilatable: and being lost on death, all the above, on cooling, shrinks and contracts, whence comes the increase in weight, as I have often said. What is there in lead like this? Thus the opinion of Cardan seems so frivolous, that I am grieved that a great man, who is rightly held in high esteem throughout the universe, should have declared to me a few days ago that he inclined towards it.

Essay XVIII. That it is not the consumption of the aerated particles which augments the weight of the lead

Scaliger has bound himself up so closely with Cardan, that I cannot separate the two; so here as elsewhere he must follow him. In Exercitation ci, section 18, he states that the augmentation in weight of calcined lead comes from its aerated particles being consumed by the fire: for the same reason, says he, as baked tile weighs more than unbaked. Oh how the superficial resemblance of things sometimes deceives fine understandings! This great man seeing that the calx of lead and the tile after treatment with fire both become heavier, thinking of the same effect, has sought only one and the same cause. The causes are very diverse notwithstanding. The tile increases in weight by decreasing in extension: the calx, because of the addition of matter. And in order to make this better understood, who does not know that tile is made of a rich and sandy earth kneaded up with water? And that the Sun absorbing its humidity leaves in it an infinite number of little cavities which were originally filled with water? When it is baked in the kiln, the heat softens it, like metals, and takes it to such a point that it almost melts, and does in fact melt if the heat is excessive. During this softening the particles shrink together, unite, and become attached to each other; the cavities disappear, and contraction thus occurs: thence comes its great weight, as I have often stated. As to lead, it melts on the fire, as is well known; and being melted, fills the vessel at all points, leaving no trace of air within itself, in accordance with the privilege that nature has granted to ponderous and fluid bodies of forcing upwards bodies which are less so, and sinking down within them. This lead taken off, loses its heat little by little: while it closes up and coagulates, shrinking into itself, and diminishing in volume, as is apparent from the dimple which is seen on the surface when it has cooled: so that it is impossible to imagine the presence of air enclosed in that heavy mass. Melt it again and calcine it, you will find it heavier: not from the consumption of aerated particles, seeing that there were none in it; but by reason of the condensed air which has united with it, as I have already said. And as a matter of fact if it lost some aerated particles, would it not decrease in volume? On the contrary it increases. And again, why do not stones and plants increase in weight on calcination if the reason be valid? I infer from the above that the consumption of aerated particles never augments the weight of things when shrinkage does not result; which not being the case in our affair, cannot be admitted as the cause of the surplus weight of which I discourse. I add in conclusion that the air which is forced by a syringe into a globe already full of it, diminishes the weight on escaping, far from increasing it as Scaliger fancies. It is true that this is met with only in this one case.

Essay XIX. That it is not soot which augments the weight of the calx.

I read in the tenth chapter of the sixth book of the Chemical Arcana by Libavius (for I have not seen it elsewhere) that Caesalpinus has written, that it is a remarkable thing that lead on calcination increases in weight by eight or ten pounds per cent. Then, seeking the cause, he says that it is due to the soot which the fire produces striking the vault of the furnace and by reflection falling back on the substance. This Caesalpinus would never have advanced had he paid attention to what I am about to deduce. Firstly, the soot on being exhaled by the fire is of so rare a nature, that the seven ounces of increase found by the sieur Brun would occupy more space than all the calx he derived from the calcination. In the second place, this abundance of soot would so blacken the calx of tin or lead, that the Ladies would never borrow from it the whiteness of their complexions, as several do. And again, what would hinder the quantity of this calx from being infinitely increased, since the fire may be continued as long as we wish, and will always furnish soot? Let us add that the sieur Brun calcined his tin on a naked and open fire so that the soot was only able to pass on one side by the dampers of the furnace and not to fall on the substance, on which also it could not descend, not being so heavy as the air contained in the vessel. As to Libavius, he has rejected this opinion of Caesalpinus, and even says that apprentices in chemistry will laugh thereat, without however adducing much against it: having enveloped his opinion in such a mass of words that it is not easily extracted from them. Thus he wishes the following words to pass as a solution of the doubt: That transmutation alters weight; and a few lines further on: That burning augments the weight of lead. Better to see the energy of these replies, it is only needful to diversify a very little the terms of our question, the sense remaining still the same, and adapt them as follows: Why does the transmutation of lead into calx change the weight? because, he says, transmutation changes the weight. Why does burning augment the weight of lead? because, he says, burning augments the weight of lead. See I pray you if what he says of the reason of Caesalpinus is applicable to his own. Assuredly one needs not to be a great Chemist, or a great Logician withal, to laugh at it. Receive his reasons who will, they shall never be accepted by me. But I am ashamed to discover the shame of this person, whose merit in other respects is great on account of the number of writings he has made public, which are filled with much sound doctrine.

Essay XX. That the augmentation of the calx of tin and lead does not come from the vessel.

I come to opinions which have not been written, at least as far as I am aware. Since nothing touches the tin and lead on calcination except the air and the containing vessel, those who will not acknowledge the former as the cause of the increase in weight, cannot I think with any plausibility have recourse to anything but the latter. For they might persuade themselves that in the calcination and incessant agitation of the said metals, the iron being burnt might become friable on its surface, a portion of which would mix with the calx and thus increase its weight. Just as the pearls, which the Pharmacist brays on his marble acquire a greater weight by the addition of the stony matter which, being crumbled, mixes with them; very often to the prejudice of those to whom they are afterwards given. But in order to rid them of that opinion, I represent firstly, that if the powdered iron, which is brown, became mixed to so great an extent with the tin, it would darken its calx, which nevertheless is always white. Secondly, if the vessel were consumed in this way, it would be useless after two or three calcinations: whereas it lasts for several years, although used daily. Thirdly, from a very little tin or lead one might extract the calx in abundance, it being thus easy to reduce all the vessel to powder by continuation of the fire, which is contradicted by experiment. What is more, Modestinus Fachsius has observed (as Libavius reports at the place already indicated) that in the examination of metals, the vessel, the cupel, the lead, and the metal examined, are all heavier after the examination than before exposure to the fire; although there has been a loss of much matter dissipated as fumes: which can only happen by the adhesion to all this of much of the air above-mentioned, a thing which has hitherto not been comprehended. So on this account the vessel for the calcination may be found too heavy, and I beg the sieur Brun to attend to it.

Essay XXI. That it is not the vapours from the charcoal that augment the weight.

It has been reported to me (I know not if faithfully) that an intimate friend of mine, a man of profound knowledge, and of most refined and substantial judgment, to whom the sieur Brun had made the same request as he made to me, has allowed himself to be led to the belief that the augmentation of weight in question proceeds from the vapours of the charcoal, which passing through the vessel, mingle with the calx. This I maintain to be impossible. For if such vapours cannot pass through a beaker of glass, a plate of tin, an earthen pot (otherwise our broths, sauces, and soups would be infected with them), how shall they traverse an iron vessel, the material of which is so much stronger? If the most subtle air cannot penetrate it (of what use else would be my Aeolipyle?) how shall these gross vapours penetrate it? and having penetrated it, what impediments will they find in the calx to be there arrested? why should they there finish their course? The heat by its vehemence expels from the tin and the lead the humidity which bound their particles together, driving off all the metallic vapours, although these are natural to them. And it will leave these foreign vapours? It seems not very probable. O truth, how dear thou art to me, thus to make me strive against so dear a friend!

Essay XXII. That it is not the volatile salt of the charcoal which augments the weight.

As soon as I had made a rough sketch of this discourse, I sent it to the person of whom I have spoken in the preceding Essay. A few days thereafter he put into my own hands a manuscript disavowing the opinion which I have combatted. And after having opposed to my belief touching the increase of density and heaviness of heated air the reasons which I have given in the twelfth Essay, and refuted in it as well as in the two Essays following: he puts forth his opinion as I give it succinctly here. That the augmentation of which we treat comes necessarily either from the vessel, or from the air, or else from the charcoal. Not from the vessel, as it loses nothing of its weight: nor from the air, since heat can only subtilize it and make it less heavy, as he presupposes to have shown; it follows then, he says, that it is the charcoal to which the augmentation is due. And to show how that occurs, he says that charcoal contains two parts or natures, one vegetable, the other metallic; and each of these two others, one fixed, the other volatile. That the fixed part remains at the bottom of the furnace in the form of ashes, in which the fixed salt is contained and may be separated by ablution: and the volatile part ascends all around the vessel, containing in a superfluous humidity (which is due to the vegetable part) a volatile salt of metallic nature, which being raised on the wings of the humidity and meeting the air directly above the vessel (more rarefied and less heavy than the vapour which comes from the charcoal) sinks through it into the vessel, and attaches itself by a close sympathy to the fixed salt of the calx of tin, which, having taken up a certain quantity of it, and being as it were satiated, rejects the surplus: just as the salt of tartar after a certain number of cohobations cannot impregnate itself more with the volatile salt contained in brandy. Having perused his paper, I refuted this opinion in his presence by the following reasons. Since we must believe everyone on the subject of his own art, if we have nothing to the contrary, it is reasonable that in speaking of the volatile salt we borrow the language of the Spagyrics, who alone can properly discourse of it, having discovered it first and revealed it to us, when we never thought that a volatile salt existed in nature. They recognise in vegetables (as in almost all things) two sorts of salt, one fixed, and the other volatile; the former containing a fixed spirit, and being contained in the solid parts of its subject; the other containing a volatile spirit, and being contained in the juices. The fixed is extracted, so they tell us, by calcination, remaining in the ashes. The other cannot endure fire (being in fact as in name, volatile), but flies off at the least heat with the juice containing it: or is lost by the simple drying up of the vegetable. Now, this being so, it is beyond doubt, that in charcoal there is no volatile salt at all; seeing that even in the wood of which it is made there can be none, since it is dried beforehand: and even if there were some in it, who does not see that it would of necessity be lost, when, on heating, the wood is reduced to charcoal? Indeed, although I admitted unjustly that charcoal contains some volatile salt, those who know how rare this salt is in all things, will never be persuaded that from the small amount of charcoal consumed by the sieur Brun in his calcination, so great a quantity could have proceeded. For it is not merely necessary to imagine only seven ounces of it: but also what replaced the decrease of weight caused by the loss of vapours from the tin and the aggrandisement of its volume: and besides what the smoke from the charcoal carried elsewhere, not only throughout the laboratory, but without it, whither the vapours were copiously poured though its openings. If in these fumes there were salt in proportion to that which fell into the vessel from the fumes above it, and the whole were gathered into one mass, truly the quantity of it would be monstrous. And then, when the calx of tin should have satiated itself with salt by this imaginary sympathy, what would prevent the continued heating to deposit more on the top of it, and fill the vessel, since it descends into it by its proper heaviness? Experience refutes all this: and moreover I have proved that the air above the vessel is so dense that the salt could not descend in it. In addition, if a furnace is erected in a wall separating two chambers in such wise that the vessel is on one side, and the doors and dampers to introduce charcoal and admit air are on the other, I maintain that the augmentation will take place, although no vapours can enter the chamber in which the vessel is placed. And this I confirm by the experiment which I made at the iron-works of Jean Rey sieur de la Perrotasse, my eldest son, where I found a similar augmentation with tin which I calcined on a pig, as they call it, or an ingot of sixteen to twenty hundredweights of iron, at the moment when, issuing from the furnace, it was poured into its mould. For no one can say that the vapours from charcoal had contributed anything here. Therefore the volatile salt is not admissible in this matter.

Essay XXIII. That the mercurial volatile salt is not the cause of this augmentation.

Some days after the refutation which I have just recounted, the same person wrote me another opinion of his. Namely, that the volatile salt is of mercurial nature, having no one of the principles in it entirely pure, but mixed with the others: so that in the salt there is the true fixed salt, then another less terrestrial, partaking of the nature of sulphur; then another still more subtle and penetrating, which partakes of the nature of mercury. Now, crude cold mercury easily penetrates iron, and attaches itself closely to it, both internally and externally; so that it is not unreasonable to be of opinion that the volatile salt of mercurial nature, rarefied by fire and rendered much more penetrating, should succeed in passing through the thickness of the vessels, similarly heated by the fire and made more easily penetrable, and should attach itself to the calx of tin by a certain sympathy which can subsist between them, as well as between gold and crude mercury. This second opinion is sufficiently destroyed by the reasons of the preceding Essay; for having shown that in charcoal there can be no volatile salt, who does not see it cannot subsist therein in any fashion? Again, if this salt of mercurial nature penetrate the vessels, it will necessarily dissolve them, and make of them an amalgam, which does not happen in our calcination. Besides, crude mercury being exhaled as we see, has a very small heat; how then can it happen that this mercurial salt, of so subtle a nature, having penetrated the vessel should persist in the still burning calx without swiftly flying off? Again, if we are to find in each of these principles all three, I do not see why they cannot all be found in each of these again, and why we should not go on in this way ad infinitum. These are speculations subtle indeed, but having no foundation in nature.

Essay XXIV. That it is not humidity attracted by the calx which augments its weight.

Not long since, speaking to a learned and judicious man, it occurred to me to discover this question to him, whereupon, having thought a little, he told me his belief was that the augmentation was due to the fact that the tin by its great dryness attracted to itself much humidity, which made it so heavy. But I cannot approve this opinion for the reasons that follow. Firstly, because I have never learned that a contrary will attract its contrary: it flees from it rather, or banishes it if it can. Then by humidity he cannot mean a bare quality, but water or air endowed with it. As for water, whence would the calx get it, having none in its neighbourhood? Will there be found in the laboratory where the calcination is performed, air more humid than the common? Will not the heat of the furnace have absorbed it? And although this calx should attract enough water or moist and nebulous air to increase its weight by a fifth or thereby as experiment proves, we should then have mortar instead of a dry calx. I will add that at the instant of calcination the calx has augmented in weight before it has the time to exercise this imaginary attraction.

Essay XXV. By a single experiment all opinions contrary to mine are entirely destroyed.

It is said of Hercules that no sooner had he cut off one of the heads of that Hydra which devastated the Lernaean marsh, than two others sprang forth. My condition is similar. The error that I combat teems with opinions, which are so many heads: if I cut off one, we see two appear. My labour is always on the increase: and I believe I should never have done if I only employed myself in cutting off one after the other. To give it the deathblow, I must gather my strength and make stiff my arm, in order that I may strike them all off at a single blow. Let him who will take heed: for now the fatal stroke will be dealt him. I have just read in Hamerus Poppius, in the third chapter of his book entitled Basilica Antimonii the new method which he practises to calcine antimony. He takes a certain quantity of it, weighs it, and places it in the fashion of a cone on a slab of marble, then having a burning mirror, he opposes it to the Sun, and directs the pyramidal point of the reflected rays on the point of the cone of antimony, which straightway fumes abundantly, and in a little while, what the rays have touched is converted into a very white calx, which he separates with a knife, and conducts the rays on the remainder till all has become white: and then the calcination is ended. It is a remarkable thing (he adds) that although in this calcination the antimony has lost much of its substance, by the vapours and fumes which are copiously exhaled, yet its weight augments instead of diminishing. Now if we seek the cause of this augmentation: will Cardan say that it is the vanishing of the celestial heat? It is even infused into it more largely by the solar beams. Will Scaliger say that it is the consumption of the aerated particles? But on being broken up into calx and increasing in volume, more of these are thrust into it. Will Caesalpinus allege soot? There is no fire to produce any. Would the vessel furnish something on its part? The rays are conducted so dextrously on the substance that they do not touch the marble. Will anyone suggest the vapours of charcoal? None is used in this affair. As to the volatile salts which have been so ingeniously brought forward, they here lose their savour and their charm. Peradventure someone will put humidity to the fore, as has quite lately been done. But whence would it come? from the marble? nay nay, that is not imaginable. From the air? still less, for this operation should succeed best in the hottest days of operation should succeed best in the hottest days of Summer, in the most violent ardours of the Dog-days, when everything below is so heated, that even in the shade and in the night-time the air dries soaked linen, and parches the moist earth. And, during the day, where the Sun strikes, he burns our complexions, withers the grass, scorches fruits, desiccates wood, dries up lakes, lowers rivers, and inflames combustible things like pigeons' droppings. To seek humidity in the air wherewith to moisten our calx and make it heavier in that fashion--not by night but in the daytime, not in the shade but in the Sun, and not where he simply shines but where his beams gathered in a concave mirror are reflected with such violence that they melt and calcine the metals--to seek humidity there, I say, is to seek fire in ice and a knot in a bulrush, as they say, a thing which never can be found. Let now all the greatest minds in the world be fused into one mind, and let this great mind strain every nerve beyond its power; let him seek diligently on the earth and in the heavens, let him search every nook and cranny of nature: he will only find the cause of this augmentation in the air when the Sun's rays heat it, and render it dense and heavy, so that it then mixes with the calx as the antimony on calcination crumbles and becomes adherent in its minutest particles. And this confirms entirely the truth of my belief in the augmentation of lead and tin: which can have no other cause than the admixture of condensed air, there being no difference between the increase of weight in these two metals and in antimony, only that in the last case the air is condensed by the solar rays, and in the former by the heat of the common fire.

Essay XXVI. Why the calx does not increase in weight infinitely.

Having thus repulsed contrary opinions, mine alone can hold the field freely. It is true that perceiving certain objections which might encumber its path, I will now go forward to remove them. The first would seem to lead us to the absurdity to which I took exception in the case of Caesalpinus, namely, that my opinion being granted, the calx of which I treat might increase in weight ad infinitum. For why, one will say, should not the calx increase infinitely, the fire being infinitely continued so as always to furnish that dense and heavy air to increase it? I escape this difficulty, which might entangle some less subtle, by remarking that all matter which is increased by the addition of another matter is either solid or liquid, and that the mixing of them may occur in three fashions. For either the solid matter mixes with solid, or liquid with liquid, or liquid with solid. The mixing and increase which occurs in the first two cases has no limit. Mix with the sand and add to it some other sand, and you will go on increasing it without end. Mix with this wine and pour into it some other wine, and you never will have done. It is not the same in the third case, when a liquid is added to and mixed with a solid: such a mixed addition will not increase always, will not go on infinitely. Nature in her inscrutable wisdom has here set limits which she never oversteps. Mix water with sand or meal and they will be entirely covered by it, down to the least of their particles: pour on more, they will not take it up; and on withdrawing them from the water they will only carry what adheres to them and suffices properly to enclose them. Plunge them in again a hundred times and yet again a hundred, they will come out no better charged; and when left to themselves within it, they will leave the superfluous water and sink to the bottom of themselves: so scrupulous is nature to stop at the limits which she has once prescribed herself. Our calx is in this condition: "the condensed air becomes attached to it, and adheres little by little to the smallest of its particles: thus its weight increases from the beginning to the end: but when all is saturated, it can take up no more." Do not continue your calcination in this hope: you would lose your labour. For the rest, let not that trouble you which was said in the eleventh Essay, namely, that I almost called that air no longer air but an unnatural air: for these are words of excess, by which I mean nothing more than that the air has been deprived of that liquid subtlety which caused it not to adhere to any substance, and has become gross, heavy, and adherent.

Essay XXVII. Why all other calces and ashes do not increase in weight.

I come to another objection which might be raised. Why do not all other calces and ashes made by the force of fire increase in weight as well as the calx of tin and of lead? What privilege have these over the others? I answer that the things calcined or incinerated are of different nature. Some have much exhalable and evaporable matter, or (speaking spagyrically) much sulphur and mercury, which the fire expels to the end. Here there is much diminution and little ash, which cannot attach to itself as much of the air condensed by fire as even to make up for the decrease. Others have little exhalable and evaporable matter, or little sulphur and mercury: consequently there is little diminution, much ash (from the abundance of salt) which attracts so much of the condensed air, that not only is the diminution made good, but the weight increases largely in addition. Stones, vegetables, and animals are usually in the first named class. Lead and tin in the second. There are other things which calcination carries to such increase of volume, that even if little or no matter were lost, the weight would nevertheless be much diminished, not so much when examined by aid of the reason as when examined by the balance. Such are the Indian metal named Calaem [Zinc--Alembic Club Eds.], and a species of crocus of iron, such as Chemists can exhibit.

Essay XXVIII. Whether lead increases in weight as well as tin.

I should have ended, were it not that the sieur Brun informs me in his letter, that having noticed the augmentation of tin, he made the same experiment with lead, which he found to diminish by one ounce in the pound: which sank him still deeper in doubt, having imagined that the same increase should be there found as with tin, from the proximity of their nature and from the identity of the process of calcination. But to the experiment of the sieur Brun I oppose the experiments of Cardan, of Scaliger, and notably of Caesalpinus already mentioned, who says it is worth of astonishment that lead on calcination increases in weight by eight to ten pounds in the hundred. Shall I leave these persons in strife each to sustain his own experiment? I am too pacific: behold their reconciliation effected. Some lead is more pure than others, either because it comes so from the ores or because it has been previously melted. Those named above have found augmentation with the pure lead: the sieur Brun a diminution with the other.

Conclusion.

Behold now this truth, whose brilliance strikes the eye, which I have drawn from the deepest dungeons of obscurity. This it is to which the path has been hitherto inaccessible. This it is which has distressed with toil so many learned men, who, wishing to know it, have striven to clear the difficulties which held it encircled. Cardan, Scaliger, Fachsius, Caesalpinus, Libavius, have curiously sought it, but never perceived it. Others may be on its quest, but vainly if they fail to follow the road which I first of all have made clear and royal: all others being but thorny footpaths and inextricable byways which lead never to the goal. The labour has been mine; may the profit be to the reader, and to God alone the glory.