Buffon's Natural History. Volume X (of 10)

We must not, however, conclude that Nature really performs by the means of water all that we do by fire. The decomposition of every substance is only to be made by division, and the greater this division the more the decomposition will be complete. Fire seems to divide as much as possible those matters which it fuses; nevertheless it may be doubted whether those which water and acids keep in dissolution are not still more divided, and the vapours raised by heat contain matters still further attenuated, in the bowels of the earth, then, by the means of the heat it includes, and the water which insinuates, there is made an infinity of sublimations; distillations, chrystallizations, aggregations, and disjunctions, of every kind. By time all substances may be compounded and decompounded by these means; water may divide and attenuate the parts more than fire when it melts them, and those attenuated parts will join in the same manner as those of fused metal unite by cooling. Crystallization, of which the salts have given us an idea, is never performed but when a substance, being disengaged from every other, is much divided and sustained by a fluid, which having little or no affinity with it, permits it to unite and form by virtue of its force of attraction, masses of a figure nearly similar to its primitive parts. This operation, which supposes all the above circumstances, may be done by the intermediate aid of fire as well as by that of water, and is often accomplished by the concurrence of both, because all this exacts but one division of matter sufficiently great for its primitive parts to be able to form, by uniting figured bodies like themselves. Now fire can bring many substances to this state much better than any other dissolvent, as observation demonstrates to us in asbestos, and other productions of fire, whose figures are regular, and which must be looked upon as true crystallizations. Yet this degree of division, necessary to crystallization, is not the greatest possible, since in this state the small parts of matter are still sufficiently large to constitute a mass, which like other masses, is only obedient to the sole attractive force, and the volumes of which, only touching in points, cannot acquire the resultive force that a much greater division might perform by a more immediate contact, and this is what we see happen in effervescences, where at once, heat and light are produced by the mixture of two cold liquors.

Light, heat, fire, air, water, and salts, are steps by which we descend from the top of Nature’s ladder to its base, which is fixed earth. And these are at the same time the only principles that we must admit and combine for the explanation of all phenomena. These principles are real, independently of all hypotheses and all method, as are also their conversion and transformation, which are demonstrated by experience. It is the same with the element of earth, it can convert itself by volatilizing and taking the form of the other elements, as those take that of earth in fixing; it, therefore, appears quite useless to seek for a substance of pure earth in terrestrial matters. The transparent lustre of the diamond dazzled the sight of our chemists, when they considered that stone as a pure elementary fire; they might have said with as much foundation, that it is pure water, all the parts of which are fixed to compose a solid diaphanous substance. When we would define Nature, the large masses should alone be considered, and those elements have been well taken notice of by even the most ancient philo sophers. The sun, atmosphere, earth, sea, &c. are all great masses on which they established all their conclusions; and if there ever had existed a planet of phlogiston, an atmosphere of alkali, an ocean of acid, or a mountain of diamonds, such might have been looked upon as the general and real principles of all bodies, but they are only particular substances, produced, like all the rest, by the combinations of true elements; and ideas to the contrary would never have been started but upon the supposition that the earth was neither more simple nor less convertible than either of the other elements.

In the great mass of solid matter, which the earth represents, the superficial is the least pure. All the matter deposited by the sea, in form of sediment, all stones produced by shell-animals, all substances composed by the combinations of the waste of the animal or vegetable kingdom, and all those which have been changed by the fires of volcanos, or sublimated by the internal heat of the globe, are mixed and transformed substances; and although they compose great masses they do not clearly represent to us the element of earth. They are vitrifiable matters, whose mass must be considered as 100,000 times more considerable than all those other substances, which should be regarded as the true basis of this element. It is from this common foundation that all other substances have derived the origin of their solidity, for all fixed matter, however much decomposed, subsides finally into glass by the sole action of fire: it resumes its first nature, when disengaged from the fluid, or volatile matters, which were united with it; and this glass, or virtreous matter, which composes the mass of our globe, represents so much the better the element of earth, as it has neither colour, smell, taste, liquidity, nor fluidity, qualities which all proceed from the other elements, or belong to them.

If glass be not precisely the element of earth, it is at least the most ancient substance of it; metals are more recent, and less dignified; and most other minerals form within our sight. Nature produces glass only in the particular focus of its volcanos, whereas every day she forms other substances by the combination of glass with the other elements. If we would form to ourselves a just idea of her formation of the globe, we must first consider her processes, which demonstrate that it has been melted or liquefied by fire; that from this immense heat it successively passed to its present degree; that in the first moments, where its surface began to take consistence, inequalities must be formed, such as we see on the surface of melted matters grown cold: that the highest mountains, all composed of vitrifiable matters, existed and take their date from that moment, which is also that of the separation of the great masses of air, water, and earth; that afterwards, during the long space of time which the diminution of the heat of the globe to the point of present temperature supposes, there were made in these mountains, which were the parts most exposed to the action of external causes, an infinity of fusions, sublimations, aggregations, and transformations, by the fire of the sun, and all the other causes which this great heat rendered more active than they at present are, and that consequently we must refer back to this date the formation of metals and minerals which we find in great masses, and in thick and continued veins. The violent fire of inflamed earth, after having raised up and reduced into vapours all that was volatile, after having driven off from its internal parts the matters which compose the atmosphere and the sea, and at the same time sublimated all the least fixed parts of the earth, raised them up and deposited them in every void space, in all the cavities which formed on the surface in proportion as it cooled; this, then, is the origin and the gradation of the situation and formation of vitrifiable matters which fire has divided, formed and sublimated.

After this first establishment (and which still subsists) of vitrifiable matters and minerals into a great mass, which can be attributed to the action of fire alone, water which till then formed with air only a vast volume of vapours, began to take its present state; it collected and covered the greatest part of the surface of the earth, on which, finding itself agitated by a continual flux and reflux, by the action of winds and heat, it began to act on the works of fire: it changed, by degrees, the superficies of vitrifiable matters; it transported the wrecks and deposited them in the form of sediments; it nourished shell-animals, it collected their shells, produced calcareous stones, formed hills and mountains, which becoming afterwards dry, received in their cavities all the mineral matters they could dissolve or contain.

To establish a general theory on the formation of Minerals, we must begin then by distinguishing with the greatest attention, first, those which have been produced by the primitive fire of the earth while it was burning with heat; secondly, those which have been formed from the waste of the first by the means of water; and thirdly, those which in vol canos, or other subsequent conflagrations, have a second time undergone the proof of a violent heat. These three objects are very distinct, and comprehend all the mineral kingdom; by not losing sight of them, and by connecting each substance, we can scarcely be deceived in its origin, or even in the degrees of its formation. All minerals which are found in masses, or large veins in our high mountains, must be referred to the sublimation of the primitive fire; all those which are found in small ramifactions, in threads or in vegetations, have been formed only from the waste of the first hurried away by the stillation of waters. We are evidently convinced of this, by comparing the matter of the iron mines of Sweden with that of our own. These are the immediate work of water, and we see them formed before our eyes; they are not attracted by the load stone; they do not contain any sulphur, and are found only dispersed in the earth; the rest are all more or less sulphureous, all attracted by the load stone, which alone supposes that they have undergone the action of fire; they are disposed in great, hard, and solid masses: and their substance is mixed with a quantity of asbestos, another index of the action of fire. It is the same with other metals: their ancient foundation comes from fire, and all their great masses have been united by its action; but all their crystallizations, vegetations, granulations, &c. are due to the secondary causes, in which water is the primary agent.

EXPERIMENTS ON THE PROGRESS OF HEAT IN MINERAL SUBSTANCES

I CAUSED ten bullets to be made of forged and beaten iron; the first, of half-inch diameter; the second, of an inch; and soon progressively to five inches: and as all the bullets were made of iron of the same forge, their weights were found nearly proportionable to their volumes.

The bullet of half an inch weighed 190 grains, Paris weight; that of an inch, 1522 grains; that of an inch and a half, 5136 grains; that of two inches, 12173 grains; that of two inches and an half, 23781 grains; that of three inches, 41085 grains; that of three inches and a half, 65254 grains; that of four inches, 97388 grains; that of four inches and an half, 138179 grains; and that of five inches, 190211 grains. All these weights were taken with very good scales, and those bullets which were found too heavy, were filed.

While these bullets were making, the thermometer exposed to the open air was at the freezing point, or some degrees below; but in the pit where the bullets were suffered to cool, the thermometer was nearly ten degrees above that point; that is to say, to the degree of temperature of the pits of the observatory, and it is this degree which I have here taken for that of the actual temperature of the earth. To know the exact moment of their cooling to this actual temperature, other bullets of the same matters, diameters, and not heated, were made use of for comparison, and which were felt at the same time as the others. By the immediate touch of the hand, or two hands, on the two bullets, we could judge of the moment when they were equally cold; and as the greater or less smoothness or roughness of bodies makes a great difference to the touch; (a smooth body, whether hot or cold, appearing much more so than a rough body, even of the same matter, although they are both equally so) I took care that the cold bullets were rough, and like those which had been heated, whose surfaces were sprinkled over with little eminences produced by the fire.

EXPERIMENTS

I. The bullet of half an inch was heated white in two minutes, cooled so as to be held in the hand in 12, and to the actual temperature in 39 minutes.

II. That of an inch, heated white in five minutes and a half, cooled so as to be held in the hand, in 351/2 minutes, and to the actual temperature in one hour and 23 minutes.

III. That of an inch and an half, heated white in nine minutes, cooled so as to be held in the hand in 58 minutes, and to the actual temperature in two hours and 35 minutes.

IV. That of two inches heated white in 13 minutes, cooled so as to be held in the hand in one hour 20 minutes, and to the actual temperature in three hours 16 minutes.

V. That bullet of two inches and an half heated white in 16 minutes, cooled so as to be held in the hand in one hour 42 minutes, and to the actual temperature in four hours 30 minutes.

VI. That bullet of three inches heated white in 191/2 minutes, cooled so as to be held in the hand in two hours seven minutes, and to the actual temperature in five hours eight minutes.

VII. That of three inches and a half heated white in 231/2 minutes, cooled so as to be held in the hand in two hours 36 minutes, and to the actual temperature in five hours 56 minutes.

VIII. That of four inches heated white in 27 minutes and a half, cooled so as to be held in the hand in three hours two minutes, and to the actual temperature in six hours 55 minutes.

IX. That of four inches and a half heated white in 31 minutes, cooled so as to be held in the hand in three hours and 25 minutes, and to the actual temperature in seven hours 46 minutes.

X. That of five inches heated white in 34 minutes, cooled, so as to be held in the hand, in three hours 52 minutes, and to the actual temperature in eight hours 42 minutes.

The most constant difference that can be taken between each of the terms which express the time of cooling, from the instant the bullets were drawn from the fire, to that when we can touch them unhurt, is found to be about 24 minutes, for, by supposing each term to increase 24, we shall have 12, 36, 60, 84, 108, 132, 156, 180, 204, 228 minutes. And the continuation of the real time of these coolings are, 12, 351/2, 58, 80, 102, 127, 156, 182, 205, 232 minutes, which approach the first as nearly as experiment can approach calculation.

So, likewise, the most constant difference to be found between each of the terms of cooling to actual temperature is found to be 54 minutes, for by supposing each term to increase 54, we shall have 39, 93, 147, 201, 255, 309, 363, 417, 471, 525 minutes, and the continuation of the real time of this cooling is found, by the preceding experiments, to be 39, 93, 145, 196, 248, 308, 356, 415, 466, 522 minutes, which approaches also nearest to the first.

I made the like experiments upon the same bullets twice or thrice, but found I could only rely on the first, because each time the bullets were heated they lost a considerable part of their weight, which was occasioned not only by the falling off of the parts of the surface reduced into scoria, but also by a kind of drying, or internal calcination, which diminishes the weight of the constituent parts, insomuch that it appears a strong fire renders the iron specifically lighter each time it is heated; and I have found, by subsequent experiments, that this diminution of weight varies much, according to the different quality of the iron. Experience has also confirmed me in the opinion, that the duration of heat, or the time taken up in cooling of iron, is not in a smaller, as stated in a passage of Newton, but in a larger ratio than that of the diameter.

Now if we would enquire how long it would require for a globe as large as the earth to cool, we should find, after the preceding experiments, that instead of 50,000 years, which Newton assigns for the earth to cool to the present temperature, it would take 42,964 years, 221 days, to cool only to the point where it would cease to burn, and 86,667 years and 132 days, to cool to the present temperature.

It might only be supposed, that the refrigeration of the earth should be considerably increased, because we imagine that refrigeration is performed by the contact of the air, and that there is a great difference between the time of refrigeration in the air and in vacuo; and supposing that the earth and air cool in the same time in vacuo, this surplus of time should be reckoned. But, in fact, this difference of time is very inconsiderable, for though the density of the medium, in which a body cools, makes something on the duration of the refrigeration, yet this effect is much less than might be imagined, since in mercury, which is eleven thousand times denser than air, it is only requisite to plunge bodies into it about nine times as often as is required to produce the same refrigeration in air. The principal cause of refrigeration is not, therefore, the contact of the ambient medium, but the expansive force which animates the parts of heat and fire, which drives them out of the bodies wherein they reside, and impels them directly from the centre to the circumference.

By comparing the time employed in the preceding experiments to heat the iron globes, with that requisite to cool them, we find that they may be heated till they become white in one sixth part and a half of the time they take to cool, so as to be held in the hand, and about one fifteenth and a half of that to cool to actual temperature, so that there is a great error in the estimate which Newton made on the heat communicated by the sun to the comet of 1680, for that comet having been exposed to the violent heat of the sun but a short time, could receive it only in proportion thereto, and not only in so great a degree as that author supposes. Indeed, in the passage alluded to, he considers the heat of red-hot iron much less than in fact it is, and he himself states it to be, in a Memoir, entitled, The Scale of Heat, published in the Philosophical Transactions of 1701, which was many years after the publication of his principles. We see in that excellent Memoir, which includes the germ of all the ideas on which thermometers have since been constructed; that Newton, after very exact experiments, makes the heat of boiling water to be three times greater than that of the sun in the height of summer; that of melted tin, six times greater; that of melted lead, eight times; that of melted regulus, twelve times; and that of a common culinary fire, sixteen or seventeen times; hence we may conclude, that the heat of iron, when heated so as to become white, is still greater, since it requires a fire continually animated by the bellows to heat it to that degree. Newton seems to be sensible of this, for he says, that the heat of iron in that state seems to be seven or eight times greater than that of boiling water. This diminishes half the heat of this comet, compared to that of hot iron.

But this diminution, which is only relative, is nothing in itself, nor nothing in comparison with that real and very great diminution which results from our first consideration. For the comet to have received this heat a thousand times greater than that of red-hot iron, it must have remained a very long time in the vicinity of the sun, whereas it only passed very rapidly at a small distance. It was on the 8th of December, 1680, at 6/1000 distance from the earth to the centre of the sun; but 24 hours before, and as many after, it was at a distance six times greater, and where the heat was consequently 36 times less.

To know then the quantity of this heat communicated to the comet by the sun, we here find how we should make this estimation tolerably just, and, at the same time, make the comparison with hot iron by the means of my experiments.

We shall suppose, as a fact, that this comet took up 666 hours to descend from the point where it then was, and which point was at an equal distance as the earth is from the sun, consequently it received an equal heat to what the earth receives from that luminary, and which I here take for unity; we shall likewise suppose that the comet took 666 hours more to ascend from the lowest point of its perihelium to this same distance; and supposing also its motion uniform, we shall perceive, that the comet being at the lowest point of its perihelium, that is, to 6/1000 of the distance from the earth to the sun, the heat it received in that motion was 27,766 times greater than that the earth receives. By giving to this motion a duration of 80 minutes, viz. 40 for its descent, and 40 for its ascent, we shall have, at 6 distance, 27,776 heat during 80 minutes at 7 distance 20,408 heat also during 80 minutes, and at 8 distance 15,625 heat during 80 minutes, and thus, successively, to the distance of 1000, where the heat is one. By summing up the quantity of heat at each distance we shall find 363,410 to be the total of the heat the comet has received from the sun, as much in descending as in ascending, which must be multiplied by the time, that is, by four thirds of an hour; we shall then have 484,547, which divided by 2,000 represents the solid heat the earth received in this time of 1332 hours, since the distance is always 1,300, and the heat always equals one. Thus we shall have 242,547/2000 for the heat the comet received more than the earth during the whole time of its perihelium instead of 28,000, as Newton supposed it, because he took only the extreme point, and paid no attention to the very small duration of time. And this heat must still be diminished 242,547/2000, because the comet ran, by its acceleration, as much more way in the same as it was nearer the sun. But by neglecting this diminution, and admitting that the comet received a heat nearly 242 times greater than that of our summer’s sun, and, consequently 172/7 times greater than that of hot iron, according to Newton’s estimation, or only ten minutes greater according to this estimation; it must be supposed, that give a heat ten times greater than that of red hot iron, it required ten times more time; that is to say, 1332; consequently, we may compare the comet to a globe of iron heated by a forge fire for 13320 hours, to heat it to a whiteness.

Now we find by calculation from my experiments, that with a forge fire, we can heat to a whiteness a globe whose diameter is 2283421/2 inches in 799200 minutes, and, consequently, the whole mass of the comet to be heated to the point of iron to a whiteness, during the short time it was exposed to the heat of the sun, could only be 2233421/2 inches in diameter; and even then it must have been struck on all sides, and at the same time, by the light of the sun. Thus comets, when they approach the sun, do not receive an immense nor a very durable heat, as Newton says, and as we at the first view might be inclined to believe. Their stay is so short in the vicinity of the sun, that their masses have not time to be heated, and besides only part of their surface is exposed to it; this part is burnt by the extreme heat, which by calcining and volatilizing the matter of this surface, drives it outwardly in vapours and dust from the opposite side to the sun; and what is called the tail of the comet, is nothing else than the light of the sun rendered visible, as in a dark room, by those atoms which the heat lengthens as it is more violent.

But another consideration very different and infinitely more important, is, that to apply the result of our experiments and calculation to the comet and earth, we must suppose them composed of matters which would demand as much time as iron to cool: whereas, in reality, the principal matters of which the terrestrial globe is composed, such as clay, stones, &c. cannot possibly take so long.

To satisfy myself on this point, I caused globes of clay and marl to be made, and having heated them at the same forge until white, I found that the clay balls of two inches, cooled in 38 minutes so as to be held in the hand; those of two inches and an half, in 48 minutes; and those of three inches, in 60 minutes; which being compared with the time of the refrigeration of iron bullets of the same diameters, give 38 to 80 for two inches, 48 to 102 for two inches and a half, and 60 to 127 for three inches; so that only half the time is required for the refrigeration of clay, to what is necessary for iron.

I found also, that lumps of clay, or marl, of two inches, refrigerated so as to be held in the hand in 45 minutes; those of two inches and a half in 58; and those of three inches in 75, which being compared with the time of refrigeration of iron bullets of the same diameters, gives 46 to 80 for two inches, 58 to 102 for two inches and a half, and 75 to 127 for three inches, which nearly form the ratio of 9 to 5; so that for the refrigeration of clay, more than half the time is required than for iron.