Part 2

XXII. But the first person we have any account of, who observed these spots, was Father Christopher Scheinerus a jesuit, who applied himself to it with such diligence, that between the years 1611 and 1627 he had made fourteen hundred observations of them, which he gives an account of in his _Rosa Ursina_. The celebrated Galileus Galilei began also to observe them about the same time that Scheinerus did; and since them, the most laborious astronomers of the last and the present century, have applied themselves to making the same observations; so that this is a matter, which at present there is not the least doubt about; and although some have entertained suspicions whether these spots were in the body of the sun, or at a little distance from it; others have removed those difficulties, by demonstrating, that they are inherent in, and exist on, the superficies of the sun; for they not only revolve in the same proportion the sun does, but they most probably remain upon it during the whole time it takes in making an intire revolution, which it does in twenty-seven days, and they are to be seen compleat for half the time of that period; which could not happen, if the spots were inferior to the star.

XXIII. And whether these spots are sooty or smoaky vapours, which arise from the great furnace of the sun, as some think, or are any other different thing; it is clear, that during their continuance, the light and the heat of it reflected on the lower elemental regions, must be diminished in proportion to the size and number of the spots; and to this cause may be attributed, some of the notable diminutions of the light and heat of the sun, which we find recorded in history, provided they were not occasioned by some obstructions in the atmosphere. Mayolus tells us, that in the time of the emperor Justinian, the light of the sun for the greatest part of a year was so dim and faint, that it scarce exceeded that of the moon; and Plutarch tells us, that at the time of the death of Julius Cæsar, the light of the sun was equally feeble for a whole year together; which Virgil also takes notice of in the following verses of the Second Book of his Georgics:

_Ille etiam extincto miseratus Cæsare Romam_ _Tunc caput obscura nitidum ferrugine texit:_ _Impiaque æternam timuerunt sæcula noctem._

PARADOX VII.

_The Rays of the Sun reflected on a Concave Body, produce a greater Heat in Winter than in Summer, which Heat is greater still in Proportion to the coldness of the weather._

SECT. VII.

XXIV. The experiments to prove this, were to the admiration of all the by-standers, repeatedly made with the burning-glass of Mons. Villete, which we have spoken of before; and it was observed at the time of making them, that by so much the more cold the burning-glass was, by so much the quicker and stronger was the operation of the focus; and that by so much the warmer it was, by so much the more tardy and remiss were its effects. Among those who read these accounts, some looked upon them as wonderful, and others as incredible.

XXV. But with all this, the reason of the phenomenon is not very hidden. It is certain, that cold condenses bodies, and that heat dilates them. It is also certain, that the more dense a body is, the more apt and fit it is to cause reflection, and that it is least so, the more lax it is. From these two premises it may be clearly inferred, that the effects we have mentioned were things of course; but for a further explanation of this matter, I will say they were so from two causes; for the burning-glass by being in a warm state, must consequently be less compact and hard, and the operations of its focus more remiss and languid. In the first place, because a great portion of the rays were absorbed in the pores of the metal, which had been dilated by the heat, and made no reflection at all. Secondly, by their being dilated, and as we may say, become more spungy, the concave superficies of the metal were less smooth and equal, from whence it would follow, that many rays by being obstructed in their descent by some insensible prominences, would not make their reflection in a right line on the point of the focus. This may be better understood, by attending to the reflections of a ball, that is struck against a wall with an unequal surface; and it is a position agreed to by all the mathematicians who have treated of catoptrics, that light and heat in their reflections, follow exactly the same rules, that heavy bodies do.

XXVI. Nor is there are any difficulty in supposing, that a body as hard as metal, may undergo some insensible rarefaction when it grows warm; for in the first place, if a very intense heat can dilate metal, so as to make it break all its ligatures and become fluid, a less heat would have the same effect, in proportion to the degree of it, and might dilate and rarefy it a little. Secondly, experience teaches us, that every sort of metal is more sonorous when it is cold, than when it is warm; from whence it may be evidently inferred, that heat and cold do somewhat alter its texture; it being certain, that upon the texture, depends its being more or less sonorous.

PARADOX VIII.

_A flame extending itself upwards in a pyramidical or conic form, is occasioned by a violence done to the flame itself._

SECT. VIII.

XXVII. The endeavour of the flame to ascend, is the proof which is vulgarly exhibited, of there being an element or sphere of fire above us, by those who maintain that position; but we shall shew, that this is a very feeble proof, even admitting their own state of the case, because every thing that is lighter than the fluid that surrounds it, will, if it is not by violence restrained from doing so, rise above it, without being invited to ascend by a sphere of its own species that is aloft; and it is from hence, that flame, smoke, vapour, an infinity of elemental effluvia, and divers other species of things ascend, without the assistance or intervention of any other cause, except that of their being lighter than the inferior gross air.

XXVIII. To this we shall add, that there is not in the flame, the propensity to ascend which they suppose, and which seems to be indicated by its rising upwards in a conic form; for this ascent is violent, and not natural to the flame. We shall illustrate this paradox, by an experiment which my Lord Bacon mentions in the first Book of his Centuries. A small wax candle, fitted into an iron tube, and placed perpendicular in a vessel filled with spirit of wine, in which it must be immersed to such a depth, that when they are both set fire to, the flame of the candle shall not rise higher than that of the spirit; and you will see, the flame of the candle and that of the spirit being distinguishable by their different colour, that the flame of the candle will appear in the middle of that of the spirit, extending itself in breadth, and not in a pyramidical, but a round form, that occupies four or five times as much space, as that which it used to occupy when burning in the open air. This experiment proves, that the pyramidical form which the flame regularly assumes, is caused by the pressure of the air that surrounds it; and this is the sentiment of the modern philosophers, who without adverting to the experiment we have mentioned, would make no scruple of pronouncing, that the form it assumes is a violence done the flame.

XXIX. By this example it may be seen, that experiments, provided they are made with judgment, and attended to with subtil reflection, are the only means by which we can attain any certain knowledge of natural things; but if they are made in a lumping way, and without due attention, and exactness, they are the occasion of innumerable errors. Many have arisen, from attributing to a native inclination, or intrinsic virtue of some body, effects, which are only caused by the impulse of some other neighbouring body. Before the gravity and elasticity of the air were discovered, it was looked upon as a thing demonstrated by experience, that the water’s rising in the pump, was from its inclination to obstruct or oppose a vacuum, and now it is a thing evinced by experience, that the air is what impels it to that ascent.

PARADOX IX.

_In the composition of all vegetables, there is contained a portion of metal._

SECT. IX.

XXX. This is a novelty in physics, which has not been discovered till of late years. Mons. Gofredy of the Academy Royal, having examined the ashes of many different plants, found in them all, some fine particles that would adhere to the load-stone; from whence he concluded, that these particles were either particles of iron, or else were particles of the load-stone itself. But, as it was a doubt which had never yet been cleared up, whether the load-stone would not attract other metallic particles, which were not part of itself, nor of iron; the Lemeries father and son, made some fresh enquiries, which removed all doubts respecting the matter. They with a burning-glass melted the particles which the load-stone had attracted from the ashes of the plants; which after much sparkling, liquefied into the very form and substance of the load-stone, and of iron also; and when grown cold, formed a lump of the consistence and hardness of metal. Even in honey, after it has been distilled, have been found these particles which were attractable by the load-stone; from whence it may be inferred, that this metallic composition, exists in, and is diffused through the most subtil juice of flowers and blossoms.

XXXI. But, after all this had been done, it still remained to be ascertained, whether these particles pre-existed in the plant; or were the production of the fire, and the result of their calcination; which second opinion appeared the most probable, because there seems no difficulty in supposing, that the fire might transmute into metal some of the particles of vegetables; but there appeared a very great one, in conjecturing that so heavy a metal as iron, could rise to the summit of trees, and pervade the most subtil fibres of their leaves.

XXXII. Mons. Lemeri the son cleared up this doubt, by various subtil and curious experiments, which not only evinced the volatility of iron, but also excited a belief, that this metal contributed greatly to promote the vegetation of all kinds of plants. The most remarkable experiment he made was the following one. Having poured spirit of nitre upon the filings of iron, there succeeded a violent effervescence, which after some time ceased, and left the metal dissolved into a red liquid; by afterwards pouring oil of tartar per deliquium to this liquid, another fermentation was excited, which went on increasing, till, at last, it formed on the sides of the vessel, various subtil branches, which after all the sensible fermentation had ceased, continued to grow till they reached the top of the vessel.

XXXIII. And although the first time he made this experiment, he obtained only the rude lineaments of a tree, by varying afterwards the quantity of the oil of tartar, till he hit upon the just proportion of it, he obtained a perfect metallic vegetation, and produced a tree completely formed, with its roots, trunks, branches, leaves, and flowers. This able chymist concluded from his various observations on this matter, that both the volatility, and the vegetation, were owing to the filings of the iron; for without them, he could only produce some crystalline lumps at the bottom of the vessel, which he concluded proceeded from the nitre that had been dissolved. Whoever is desirous of knowing more of the manner and effects of these operations, may read the accounts of them in the Journals of the Academy Royal, of November 1706.

XXXIV. But we are not to conclude from hence, that metallic vegetation is only to be produced by iron. The Abbé Vallemont in his first volume, _on the natural Curiosities and Art of Agriculture_, says, that there were exhibited at Paris, such like artificial metallic vegetations, produced from gold, silver, iron, and copper. But that which was the most common, and the most in vogue there, was the vegetation procured from silver, which the chymists called the _Tree of Diana_; and which was produced in the following manner. Dissolve an ounce of silver, in two or three ounces of spirit of nitre. Evaporate this dissolution in a sand-heat; till nearly half of it is consumed. Mix the remainder in a vessel, properly proportioned and suited for the business, with twenty ounces of clear water, and two ounces of quick-silver. By leaving this mixture afterwards in a state of rest for forty days, a silver tree will grow, and in that space of time will be compleatly formed, very nearly resembling a natural one, in shape and figure. Mons. Homberg, a celebrated chymist of the Academy Royal, by making use of the same materials, contrived to form a metallic tree in less than a quarter of an hour; the receipt for doing which, together with the physical explanation of this phenomenon, given by Mons. Homberg, may be seen in the Memoirs of the Academy Royal, of the thirteenth of November 1692.

XXXV. These metallic vegetations, joined to the discovery beforementioned, of our having found iron in the ashes of all sorts of plants, not only prove that metals may, by virtue of certain fermentations, be made sufficiently volatile to enable them to rise upwards, and pervade all the tubes through which the alimentary juices of plants circulate, but also make it probable, that to this metallic mixture, they in great measure owe their vegetation.

XXXVI. This is the substance of what, in support of this paradox, I have found in the Works of the before-quoted philosophers; to which I shall add a conjecture of my own, which appears to me very efficacious to render credible, the formal existence of particles of iron, or load-stone, in all vegetables whatever; whether they are of load-stone, or iron, makes very little difference, as all experimental philosophers are agreed, that load-stone is nothing else but a fat or rich vein of iron.

XXXVII. My conjecture is founded on a theory, which is embraced at present by all the mathematicians, and confirmed by conclusive reasonings, which are founded on the earth being endued with a magnetic virtue. The truth of this theory, is proved by innumerable observations. It has been found, that the magnetic needle poised in equilibrio, accommodates itself to the meridian of the earth, in the same manner the load-stone does, that is, it does not point to the poles of the heavens, but to those of the earth; for it has been observed in the northern regions, that it does not appear to elevate or point towards the pole of the heavens, but rather seems to depress, or point down towards that of the earth; and generally, in all, and every particular, the magnetic needle has been found to be affected in the same proportions with respect to the terraqueous poles, that it is with respect to the load-stone. The various declinations that it is liable to, from the pole of the earth, in different places, cannot be attributed to any other cause, than that of the unequal magnetism, of the terraqueous globe in different regions; and the different declinations of the poles of the load-stone are attributed to the unequal magnetism or perfection of the parts of the stone. It has been found, that the earth itself, can communicate the magnetic virtue to iron; for if you take a bar of iron red-hot from the forge, and place it perpendicular in the earth, and there let it remain till it becomes cold, it will manifestly acquire the magnetic virtue; and if it is afterwards poised in equilibrio, it will point to the poles of the earth, in the same manner as if it had been touched by a load-stone. It will also acquire the same virtue, if it has remained for many years in a perpendicular position, without its having been placed so in the earth red-hot; and the same has been experienced with respect to bars, that have been set before windows in an upright position. The same effect will also be produced, by laying a hot bar upon the ground, exactly in a north and south direction, till it gets cold; but if it is so laid without being previously heated, and suffered to continue in that position for several years together, it will be found to be impregnated with the magnetic virtue. Whoever is desirous of seeing an account of these observations more at large, and to satisfy himself how they evince the magnetical quality of the earth, should read the mathematical authors who treat of the load-stone, and he will find, that all the modern ones make some remarks upon that particular.

XXXVIII. This magnetic property of the terraqueous globe being admitted, it may be inferred from it, that excepting the exterior crust of the earth, which is composed of such heterogeneous parts, as are necessary for the growth and increase of the various productions and mixtures with which it abounds, all the rest, is nothing else, but a solid quarry of load-stone; and this is the opinion that is strenuously maintained by some; although there are others, who think that the magnetic virtue, is distributed through all the parts of the terraqueous globe.

XXXIX. Both these opinions may be right, for they do not seem incompatible one with another; but in favour of the second, which is that which conduces best to support my sentiment, we may urge another celebrated piece of experience, which evinces efficaciously, that this very exterior earth which we touch and stand on, is impregnated with many insensible particles of load-stone or iron; and this is manifest, from the earth itself being endued with this magnetic virtue, or inclination of pointing to the pole; for bricks that are made from it, and are well burned and purged or freed from all foreign humour or moisture, and especially if they are made long and narrow, by being touched with a load-stone will acquire the virtue of pointing to the poles; and they will even acquire it without being touched, if they are laid in a north and south position, and suffered to continue so for many years together. (See Father Dechales, lib. 1 & 2, de Magnete.) It being then certain, that this quality of pointing to the pole, is peculiar to the load-stone, or the iron, and incommunicable to all other substances, it must evidently be inferred from this property in the bricks, that the very earth we touch and stand upon, is impregnated with particles of load-stone or iron. All vegetables then receiving their nourishment from the earth, it is not wonderful that there should be found in them all, some of these particles.

XL. I would recommend it to those who take delight in philosophy, to endeavour to inform themselves, whether it is not probable, that all other mixtures are impregnated with these particles; for if that should be found to be the case, we should discover the cause of the descent of heavy bodies; for there being in the earth the magnetic virtue, and in all other mixtures particles of iron, in spite of all our endeavours to separate them, they always would be brought together again by attraction. But as he who is a lover of the truth, should conceal no objection that may be made to any supposition that he advances, I will not dissemble, that I find a terrible one against this idea of mine; which is, that according to this system, iron should be heavier than gold; for although we should admit, that some iron, or magnetic particles are mixed with the gold, it is not credible, that the quantity of them should be equal to those in the iron itself; for if that was the case, the load-stone would attract the gold, as it does the iron. But whether there is in the terraqueous globe, another attractive quality distinct in kind from that of the load-stone, in virtue of which, all bodies may be disposed to approach it which we call heavy, by having in themselves a propensity to do it correspondent to that there is between the load-stone and the iron, is very difficult to be proved.

ON SCEPTICAL PHILOSOPHY.

SECT. I.

I. There is so great a latitude in scepticism, and its gradations are so different, that according to the various extension that is given to the meaning of the word, it is used to describe the most extravagant error, and the most prudent mode of philosophizing. Rigid scepticism is a wild delirium, moderate is prudent caution. But those who in this age, have undertaken to combat the moderate sceptics, have either from ignorance or malice, confounded them with the rigid. When I reflect how gross a thing ignorance must be in such a case, it makes me think they acted from malice, and when I consider how detestable a thing malice is, it makes me conclude what they did was through ignorance.

II. Although the Greek word _scepsis_, from whence sceptic and scepticism are derived, signifies inquisition, investigation, and speculation, custom has in a great measure altered the meaning of the term; on which account, sceptical at this day, implies doubt, or doubting; and scepticism, that particular avowal which sceptics make of doubting, or withholding their assent to all matters, that are liable to be controverted or disputed.

III. This doubt or suspension of assent, may be more or less rational, in proportion to the greater or less extent that is given to it, or according to the matters to which it relates. Thus, although doubting of many things would be prudence, doubting of all would be madness.

SECT. II.