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silver excites a slight heat, and so does copper, and tin yet more plainly, and most of all, iron and steel, which excite not only a powerful heat, but a violent bubbling. The heat, therefore, appears to be occasioned by the struggle which takes place when these strong dissolvents penetrate, dig into, and tear asunder the parts of those substances, whilst the substances themselves resist. When, however, the substances yield more easily, scarcely any heat is excited.

Twenty-sixth negative to the twentieth affirmative. There is no negative instances with regard to the heat of animals, except in insects, (as has been observed,) owing to their small size. For, in fishes, as compared with land animals, a lower degree rather than a deprivation of heat is observable. In plants and vegetables, both as to their exudations and pith when freshly exposed, there is no sensible degree of heat. But in animals there is a great difference in the degree, both in particular parts, (for the heat varies near the heart, the brain, and the extremities,) and in the circumstances in which they are placed, such as violent exercise and fevers.

Twenty-seventh negative to twenty-first affirmative.

Here again there is scarcely a negative instance. I might add that the excrements of animals, even when they are no longer fresh, possess evidently some effective heat, as is shown by their enriching the soil.

Twenty-eighth negative to the twenty-second and twentythird affirmative.

palate, and still more so when taken internally One should see, therefore, on what other sub stances they exhibit the effects of heat. Now, sailors tell us that when large quantities of spices are suddenly opened, after having been shut up for some time, there is some danger of fever and inflammation to those who stir them or take them out. An experiment might therefore be made whether such spices and herbs when produced will, like smoke, dry fish and meat hung up over them.

Thirty-first negative to twenty-sixth affirmative. There is an acrid effect, and a degree of penetration in cold liquids, such as vinegar and oil of vitriol, as well as in warm, such as oil of marjoram and the like. They have, therefore, an equal effect in causing animated substances to smart, and separating and consuming inanimate parts. There is not any negative instance as to this, nor does there exist any animal pain unaccompanied by the sensation of heat.

Thirty-second negative to twenty-seventh affirmative.

There are many effects common to cold and heat, however different in their process. For, snow balls appear to burn boys' hands after a little time, and cold no less than fire preserves bodies from putrefaction, besides, both heat and cold contract bodies. But it is better to refer these instances and the like to the investigation

of cold.

13. In the third place, we must exhibit to the understanding the instances in which that nature, which is the object of our inquiries, is present in a greater or less degree, either by comparing its increase and decrease in the same object, or its

Such liquids (whether oily or watery) as are intensely acrid, exhibit the effects of heat, by the separation and burning of bodies after some little action upon them, yet they are not at first warm | degree in different objects. For, since the form to the touch. But they act according to their affinity and the pores of the substances to which they are applied. For aqua regia dissolves gold, but not silver, on the contrary, aqua fortis dissolves silver, but not gold; neither of them dissolves glass, and so of the rest.

Twenty-ninth negative to twenty-fourth affirmative. Let spirits of wine be tried on wood, or butter, wax, or pitch, to see if this will melt them at all by their heat. For the 24th instance shows that they possess properties resembling those of heat in causing incrustation. Let an experiment also be made with a graduated glass or calendar,* concave at the top, by pouring well rectified spirits of wine into the cavity, and covering it up in order that they may the better retain their heat, then ob

serve whether their heat make the water descend.

Thirtieth negative to twenty-fifth affirmative.

of a thing is its very essence, and the thing only
differs from its form as the apparent from the
actual object, or the exterior from the interior, or
that which is considered with relation to man
from that which is considered with relation to the
universe; it necessarily follows that no nature
can be considered a real form, which does not
uniformly diminish and increase with the given
nature. We are wont to call this our table of
degrees or comparative instances.

Table of the Degrees or Comparative Instances of
Heat.

We will first speak of those bodies which exhibit no degree of heat sensible to the touch, but appear rather to possess a potential heat, or disposition and preparation for it. We will then go on to others, which are actually warm to the touch, and observe the strength and degree of it. 1. There is no known solid or tangible body

Spices and acrid herbs are sensibly warm to the which is by its own nature originally warm.

*See No. 38, in the table of the degrees of heat.

For neither stone, metal, sulphur, fossils, wood, water, nor dead animal carcasses, are found warm

The warm springs in baths appear to be heated accidentally, by flame, subterraneous fire, (such as is thrown up by Etna and many other mountains,) or by the contact of certain bodies, as heat is exhibited in the dissolution of iron and tin. The degree of heat, therefore, in inanimate objects is not sensible to our touch, but they differ in their degrees of cold, for wood and metal are not equally cold. This, however, belongs to the table of degrees of cold.

2. But with regard to potential heat and predisposition to flame, we find many inanimate substances wonderfully adapted to it; as sulphur, naphtha, and saltpetre.

3. Bodies which have previously acquired heat, as horse-dung from the animal, or lime, and perhaps ashes or soot from fire, retain some latent portion of it. Hence distillations and separations of substances are effected by burying them in horse-dung, and heat is excited in lime by sprinkling it with water, (as has been before observed.) 4. In the vegetable world we know of no plant, nor part of any plant, (as the exudations or pith) that is warm to man's touch. Yet, as we have before observed, green weeds grow warm when confined, and some vegetables are warm and others cold to our internal touch, i. e. the palate and stomach, or even, after a while, to our external skin, (as is shown in plasters and ointments.)

5. We know of nothing in the various parts of animals, when dead or detached from the rest, that is warm to the touch. For horse-dung itself does not retain its heat, unless it be confined and buried. All dung, however, appears to possess a potential heat, as in manuring fields. So, also, dead bodies are endued with this latent and potential heat, to such a degree that, in cemeteries where people are interred daily, the earth acquires a secret heat which consumes any recently deposited body much sooner than pure earth: and they tell you that the people of the East are acquainted with a fine soft cloth, made of the down of birds, which can melt butter wrapt gently up in it by its own warmth.

6. Manures, such as every kind of dung, chalk, sea-sand, salt, and the like, have some disposition towards heat.

7. All putrefaction exhibits some slight degree of heat, though not enough to be perceptible by the touch. For, neither the substances, which by putrefaction are converted into animalculæ, as flesh and cheese, nor rotten wood, which shines in the dark, are warm to the touch. The heat, however, of putrid substances displays itself occasionally in a disgusting and strong scent.

8. The first degree of heat, therefore, in substances which are warm to the human touch, appears to be that of animals, and this admits of a great variety of degrees, for the lowest (as in insects) is scarcely perceptible, the highest scarcely equals that of the sun's rays in warm climates

and weather, and is not so acute as to be insufferable to the hand. It is said, however, of Constantius, and some others of a very dry constitution and habit of body, that when attacked with violent fevers, they became so warm as to appear almost to burn the hand applied to them.

9. Animals become more warm by motion and exercise, wine and feasting, venery, burning fevers, and grief.

10. In the paroxysm of intermittent fevers the patients are at first seized with cold and shivering, but soon afterwards become more heated than at first; in burning and pestilential fevers they are hot from the beginning.

11. Let further inquiry be made into the comparative heat of different animals, as fishes, quadrupeds, serpents, birds: and also of the different species, as the lion, the kite, or man. For, according to the vulgar opinion, fishes are the least warm internally, and birds the most; particularly doves, hawks, and ostriches.

12. Let further inquiry be made as to the comparative heat in different parts and limbs of the same animal. For milk, blood, seed, and eggs are moderately warm, and less hot than the outward flesh of the animal when in motion or agitated. The degree of heat of the brain, stomach, heart, and the rest, has not yet been equally well investigated.

13. All animals are externally cold in winter and cold weather, but are thought to be internally warmer.

14. The heat of the heavenly bodies, even in the warmest climates and seasons, never reaches such a pitch as to light or burn the dryest wood or straw, or even tinder without the aid of burningglasses. It can, however, raise vapour from moist substances.

15. Astronomers tell us that some stars are hotter than others. Mars is considered the warmest after the sun, then Jupiter, then Venus. The moon and, above all, Saturn are considered to be cold. Among the fixed stars, Sirius is thought the warmest, then Cor Leonis, or Regulus, then the lesser dog-star.

The sun gives out more heat as it approaches towards the perpendicular or zenith, which may be supposed to be the case with the other planets according to their degree of heat; for instance, that Jupiter gives out more heat when situated beneath Cancer or Leo, than when he is beneath Capricorn and Aquarius.

17. It is to be supposed that the sun and other planets give more heat in perigee, from their approximation to the earth, than when in apogee. But if in any country the sun should be both in its perigee and nearer to the perpendicular at the same time, it must necessarily give out more hea than in a country where it is also in perigee, but situated more obliquely. So that the comparative altitude of the planets should be observed, and

heir approach to or declination from the perpen- from some imperfect metals is very strong and dicular in different countries. active: but on all these points further inquiry should be made.

18. The sun and other planets are thought also to give out more heat in proportion as they are nearer to the larger fixed stars; as when the sun is in Leo he is nearer Cor Leonis, Cauda Leonis, Spica Virginis, Sirius, and the lesser dog-star, than when he is in Cancer, where, however, he approaches nearer to the perpendicular. It is probable also that the quarters of the heavens produce a greater heat (though not perceptibly) in proportion as they are adorned with a greater number of stars, particularly those of the first magnitude.

19. On the whole, the heat of the heavenly bodies is augmented in three ways: 1. The approach to the perpendicular; 2. Proximity or their perigee; 3. The conjunction or union of stars.

20. There is a very considerable difference between the degree of heat in animals, and even in the rays of the heavenly bodies, (as they reach us,) and the heat of the most gentle flame, and even of all ignited substances, nay, liquids, or the air itself, when unusually heated by fire. For the flame of spirit of wine, though diffused and uncollected, is yet able to set straw, linen, or paper on fire, which animal heat, or that of the sun, will never accomplish without a burning-glass.

21. There are, however, many degrees of strength and weakness in flame and ignited bodies: but no diligent inquiry has been made in this respect, and we must, therefore, pass it hastily over. Of all flames, that of spirits of wine appears to be the most gentle, except, perhaps, the ignis fatuus, or the flashes from the perspiration of animals. After this we should be inclined to place the flame of light and porous vegetables, such as straw, reeds, and dried leaves; from which the flame of hair or feathers differs but little. Then, perhaps, comes the flame of wood, particularly that which contains but little rosin or pitch, that of small wood, however, (such as is usually tied up in fagots,) is milder than that of the trunks or roots of trees. This can be easily tried in iron furnaces, where a fire of fagots or branches of trees is of little service. Next follows the flame of oil, tallow, wax, and the like oily and fat substances, which are not very violent. But a most powerful heat is found in pitch and rosin, and a still greater in sulphur, camphire, naphtha, saltpetre, and salts, (after they have discharged their crude matter,) and in their compounds; as in gunpowder, Greek fire, (vulgarly called wild fire,) and its varieties, which possess such a stubborn heat as scarcely to be extinguished by

23. The flame of vivid lightning appears to exceed all the above, so as sometimes to have melted even wrought iron into drops, which the other flames cannot accomplish.

21. In ignited bodies there are different degrees of heat, concerning which also a diligent inquiry has not been made. We consider the faintest heat to be that of tinder, touchwood, and dry rope match, such as is used for discharging cannon. Next follows that of ignited charcoal, or cinders, and even bricks, and the like; but the most violent is that of ignited metals, as iron, copper, and the like. Further inquiry, however, must be made into this also.

25. Some ignited bodies are found to be much warmer than some flames; for instance, red-hot iron is much warmer, and burns more than the flame of spirits of wine.

26. Some bodies even not ignited, but only heated by the fire, as boiling water, and the air confined in reverberatories, surpass in heat many flames and ignited substances.

27. Motion increases heat, as is shown in the bellows and the blow-pipe, for the harder metals are not dissolved or melted by steady, quiet fire. without the aid of the blow-pipe.

28. Let an experiment be made with burningglasses; in which respect I have observed, that if a glass be placed at the distance of ten inches, for instance, from the combustible object, it does not kindle or burn it so readily as if the glass be placed at the distance of five inches, (for instance,) and be then gradually and slowly withdrawn to the distance of ten inches. The cone and focus of the rays, however, are the same, but the mere motion increases the effect of the heat.

29. Conflagrations, which take place with a high wind, are thought to make greater way against than with the wind, because, when the wind slackens, the flame recoils more rapidly than it advances, when the wind is favourable.

30. Flame does not burst out or arise unless it have some hollow space to move and exert itself in, except in the exploding flame of gunpowder and the like, where the compression and confinement of the flame increases its fury.

31. The anvil becomes so hot by the hammer, that if it were a thin plate, it might probably grow red, like ignited iron, by repeated strokes. Let the experiment be tried.

32. But in ignited bodies that are porous, so as to leave room for the fire to move itself, if its motion be prevented by strong compression, the 22. We consider that the flame which results fire is immediately extinguished; thus it is with

water.

* This notion is erroneous, but the sun is in Leo about August, when the earth has become heated by the accumulation of heat after the solstice. The maximum of heat in the day is not at noon, but about two o'clock, for the same reason.

tinder, or the burning snuff of a candle or lamp, or even hot charcoal cinders, for when they are squeezed by snuffers, or the foot, and the like, the effect of the fire instantly ceases.

33. The approach towards a hot body, increases heat in proportion to the approximation; a similar effect to that of light, for the nearer any object is placed towards the light, the more visible it

becomes.

34. The union of different heats increases heat, unless the substances be mixed. For a large and small fire in the same spot, tend mutually to increase each other's heat, but lukewarm water poured into boiling water cools it.

35. The continued neighbourhood of a warm body increases heat. For the heat, which perpetually passes and emanates from it, being mixed with that which preceded it, multiplies the whole. A fire, for instance, does not warm a room in half an hour as much as the same fire would in an hour. This does not apply to light, for a lamp or candle placed in any spot, gives no more light by remaining there, than it did at first. 36. The irritation of surrounding cold increases heat, as may be seen in fires during a sharp frost. We think that this is owing not merely to the confinement and compression of the heat, (which forms a sort of union;) but also by the exasperation of it, as when the air or a stick are violently compressed or bent, they recoil, not only to the point they first occupied, but still further back. Let an accurate experiment, therefore, be made with a stick, or something of the kind, put into the flame, in order to see whether it be not sooner burnt at the sides than in the middle of it.†

37. There are many degrees in the susceptibility of heat. And, first, it must be observed how much a low, gentle heat changes and partially warms even the bodies least susceptible of it. For even the heat of the hand imparts a little warmth to a ball of lead or other metal held a short time in it. So easily is heat transmitted and excited, without any apparent change in the body.

38. Of all bodies that we are acquainted with, air admits and loses heat the most readily, which is admirably seen in weather-glasses, whose construction is as follows. Take a glass with a hollow belly, and a thin and long neck; turn it upside down, and place it with its mouth downwards into another glass vessel containing water; the end of the tube touching the bottom of the vessel, and the tube itself leaning a little on the edge, so as to be fixed upright. In order to do this more readily, let a little wax be applied to the edge, not, however, so as to block up the orifice, lest by preventing the air from escaping, the motion, which

The fires supply fresh heat, the water has only a certain quantity of heat, which being diffused over a fresh supply of cooler water, must be, on the whole, lowered.

If condensation were the cause of the greater heat, Bacon concludes the centre of the flame would be the hotter part, and vice versa. The fact is, neither of the causes assigned by Bacon is the true one; for the fire burns more quickly only because the draught of air is more rapid, the cold, dense air pressing rapidly into the heated room and towards the chimney.

we shall presently speak of, and which is very gentle and delicate, should be impeded.

Before the first glass be inserted in the other, its upper part (the belly) should be warmed at the fire. Then upon placing it as we have described, the air, (which was dilated by the heat,) after a sufficient time has been allowed for it to lose the additional temperature, will restore and contract itself to the same dimensions as that of the external or common atmosphere at the moment of immersion, and the water will be attracted upwards in the tube to a proportionate extent. A long, narrow slip of paper should be attached to the tube, divided into as many degrees as you please. You will then perceive, as the weather grows warmer or colder, that the air contracts itself into a narrower space in cold weather, and dilates in the warm, which will be exhibited by the rising of the water as the air contracts itself, and its depression as the air dilates. The sensibility of the air with regard to heat or cold is so delicate and exquisite, that it far exceeds the human touch, so that a ray of sunshine, the heat of the breath, and, much more, that of the hand placed on the top of the tube, immediately causes an evident depression of the water. We think, however, that the spirit of animals possesses a much more delicate susceptibility of heat and cold, only that it is impeded and blunted by the grossness of their bodies.

39. After air we consider those bodies to be most sensible of heat, which have been recently changed and contracted by cold, as snow and ice; for they begin to be dissolved and melt with the first mild weather. Next, perhaps, follows quicksilver; then greasy substances, as oil, butter, and the like; then wood; then water; lastly, stones and metals, which do not easily grow hot, particularly towards their centre.* When heated, however, they retain their temperature for a very long time; so that a brick or stone, or hot iron plunged in a basin of cold water, and kept there for a quarter of an hour or thereabouts, retains such a heat as not to admit of being touched.

40. The less massive the body is, the more readily it grows warm at the approach of a heated body, which shows that heat with us is somewhat averse to a tangible mass.†

41. Heat, with regard to the human senses and touch, is various and relative, so that lukewarm

*Bacon appears to have confounded combustibility and fusibility with susceptibility of heat; for, though the metals will certainly neither dissolve as soon as ice or butter, nor be consumed as soon as wood, that only shows that different degrees of heat are required to produce similar effects on dif ferent bodies; but metals much more readily acquire and transmit the same degree of heat than any of the above substances. The rapid transmission renders them generally cold to the touch. The convenience of fixing wooden handles to vessels containing hot water illustrates these observations.

Another singular error, the truth being that solid bodies are the best conductors; but of course where heat is diffused over a large mass, it is less in each part, than if that part also alone received the whole quantum of heat.

water appears hot if the hand be cold, and cold if | as those of a lion, an eagle, a rose, gold, or the the hand be hot.

Aph. 14.

Any one may readily see how poor we are in history, since in the above tables, besides occasionally inserting traditions and report instead of approved history and authentic instances, (always, however, adding some note if their credit or authority be doubtful,) we are often forced to subjoin, "Let the experiment be tried."-"Let further inquiry be made."

like. The moment for discussing these will arrive, when we come to treat of the latent process, and latent conformation and the discovery of them as they exist in what are called substances, or concrete natures.

Nor, again, would we be thought to mean (even when treating of simple natures) any abstract forms or ideas, either undefined or badly defined in matter. For when we speak of forms, we mean nothing else than those laws and regulations of simple action, which arrange and constitute any simple nature, such as heat, light, weight, in every species of matter, and in a susceptible subject. The form of heat, or form of light, therefore, means no more than the law of heat, or the law of light. Nor do we ever ab

operative branch of philosophy. When, therefore, we say, (for instance,) in our investigation of the form of heat, reject rarity, or rarity is not of the form of heat, it is the same as if we were to say, "Man can superinduce heat on a dense body," or the reverse, "Man can abstract or ward off heat from a rare body."

15. We are wont to term the office and use of these three tables, the presenting a review of instances to the understanding; and when this has been done, induction itself is to be brought into action. For on an individual review of all the instances, a nature is to be found, such as always to be pre-stract or withdraw ourselves from things, and the sent and absent with the given nature, to increase and decrease with it, and as we have said, to form a more common limit of the nature. If the mind attempt this affirmatively from the first, (which it always will when left to itself,) there will spring up phantoms, mere theories and ill-defined notions, with axioms requiring daily correction. These will, doubtless, be better or worse, accord- But if our forms appear to any one to be someing to the power and strength of the understand- what abstracted, from their mingling and uniting ing which creates them. But it is only for God, heterogeneous objects, (the heat, for instance, of (the bestower and creator of forms,) and perhaps the heavenly bodies, appears to be very different for angels and intelligences, at once to recognise from that of fire; the fixed red of the rose and the forms affirmatively, at the first glance of contem-like, from that which is apparent in the rainbow, plation man at least is unable to do so, and is or the radiation of opal or the diamond;* death only allowed to proceed first by negatives, and by drowning, from that by burning, the sword, then to conclude with affirmatives, after every apoplexy, or consumption; and yet they all agree species of exclusion. in the common natures of heat, redness, and death,) let him be assured that his understanding is enthralled by habit, by general appearances and hypotheses. For it is most certain that, however heterogeneous and distinct, they agree in the form or law which regulates heat, redness, or death; and that human power cannot be emancipated and freed from the common course of nature, and expanded and exalted to new efficients and new modes of operation, except by the revelation and invention of forms of this nature. But after this union of nature, which is the principal point, we will afterwards, in its proper place, treat of the divisions and ramifications of nature, whether ordinary or internal, or more real.

16. We must therefore effect a complete solution and separation of nature; not by fire, but by the mind, that divine fire. The first work of legitimate induction, in the discovery of forms, is rejection, or the exclusive instances of individual natures, which are not found in some one instance, where the given nature is present, or are found in any one instance where it is absent, or are found to increase in any one instance where the given nature decreases, or the reverse. After an exclusion correctly effected, an affirmative form will remain as the residuum, solid, true, and well defined, whilst all volatile opinions go off in smoke. This is readily said, but we must arrive at it by a circuitous route. We shall, perhaps, however, omit nothing that can facilitate our progress.

18. We must now offer an example of the exclusion or rejection of natures, found by the tables of review, not to be of the form of heat; first, 17. The first and almost perpetual precaution premising, that not only each table is sufficient and warning which we consider necessary is this: for the rejection of any nature, but even each sinthat none should suppose from the great part as-gle instance contained in them. For it is clear signed by us to forms, that we mean such forms as the meditations and thoughts of men have hitherto been accustomed to. In the first place, we do not at present mean the concrete forms, which (as we have observed) are in the common course of things compounded of simple natures,

from what has been said, that every contradictory

*This general law or form, has been well illustrated by

Newton's discovery of the decomposition of colours.

i. e. the common link or form which connects the various kinds of natures, such as the different hot or red natures See Aphorism 3, Part 2.

enumerated above.

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