Chapter XXVIII (2)

8. Concerning the _uniformity_ and _duration_ of sounds, both which have one common cause, we may observe, that such bodies as being stricken yield an unequal or harsh sound, are very heterogeneous, that is to say, they consist of parts which are very unlike both in figure and hardness, such as are wood, stones, and others not a few. When these are stricken, there follows a concussion of their internal particles, and a restitution of them again. But they are neither moved alike, nor have they the same action upon one another; some of them recoiling from the stroke, whilst others which have already finished their recoilings are now returning; by which means they hinder and stop one another. And from hence it is that their motions are not only unequal and harsh, but also that their reciprocations come to be quickly extinguished. Whensoever, therefore, this motion is propagated to the ear, the sound it makes is unequal and of small duration. On the contrary, if a body that is stricken be not only sufficiently hard, but have also the particles of which it consisteth like to one another both in hardness and figure, such as are the particles of glass and metals, which being first melted do afterwards settle and harden; the sound it yieldeth will, because the motions of its parts and their reciprocations are like and uniform, be uniform and pleasant, and be more or less lasting, according as the body stricken hath greater or less magnitude. The possible cause, therefore, of sounds uniform and harsh, and of their longer or shorter duration, may be one and the same likeness and unlikeness of the internal parts of the sounding body, in respect both of their figure and hardness.

Besides, if two plane bodies of the same matter and of equal thickness, do both yield an uniform sound, the sound of that body, which hath the greatest extent of length, will be the longest heard. For the motion, which in both of them hath its beginning from the point of percussion, is to be propagated in the greater body through a greater space, and consequently that propagation will require more time; and therefore also the parts which are moved, will require more time for their return. Wherefore all the reciprocations cannot be finished but in longer time; and being carried to the ear, will make the sound last the longer. And from hence it is manifest, that of hard bodies which yield an uniform sound, the sound lasteth longer which comes from those that are round and hollow, than from those that are plane, if they be like in all other respects. For in circular lines the action, which begins at any point, hath not from the figure any end of its propagation, because the line in which it is propagated returns again to its beginning; so that the figure hinders not but that the motion may have infinite progression. Whereas in a plane, every line hath its magnitude finite, beyond which the action cannot proceed. If, therefore, the matter be the same, the motion of the parts of that body whose figure is round and hollow, will last longer than of that which is plane.

Also, if a string which is stretched be fastened at both ends to a hollow body, and be stricken, the sound will last longer than if it were not so fastened; because the trembling or reciprocation which it receives from the stroke, is by reason of the connection communicated to the hollow body; and this trembling, if the hollow body be great, will last the longer by reason of that greatness. Wherefore also, for the reason above mentioned, the sound will last the longer.

[Sidenote: How sound may be helped and hindered by the wind.]

9. In hearing it happens, otherwise than in seeing, that the action of the medium is made stronger by the wind when it blows the same way, and weaker when it blows the contrary way. The cause whereof cannot proceed from anything but the different generation of sound and light. For in the generation of light, none of the parts of the medium between the object and the eye are moved from their own places to other places sensibly distant; but the action is propagated in spaces imperceptible; so that no contrary wind can diminish, nor favourable wind encrease the light, unless it be so strong as to remove the object further off or bring it nearer to the eye. For the wind, that is to say the air moved, doth not by its interposition between the object and the eye work otherwise than it would do, if it were still and calm. For, where the pressure is perpetual, one part of the air is no sooner carried away, but another, by succeeding it, receives the same impression, which the part carried away had received before. But in the generation of sound, the first collision or breaking asunder beateth away and driveth out of its place the nearest part of the air, and that to a considerable distance, and with considerable velocity; and as the circles grow by their remoteness wider and wider, so the air being more and more dissipated, hath also its motion more and more weakened. Whensoever therefore the air is so stricken as to cause sound, if the wind fall upon it, it will move it all nearer to the ear, if it blow that way, and further from it if it blow the contrary way; so that according as it blows from or towards the object, so the sound which is heard will seem to come from a nearer or remoter place; and the reaction, by reason of the unequal distances, be strengthened or debilitated.

From hence may be understood the reason why the voice of such as are said to speak in their bellies, though it be uttered near hand, is nevertheless heard, by those that suspect nothing, as if it were a great way off. For having no former thought of any determined place from which the voice should proceed, and judging according to the greatness, if it be weak they think it a great way off, if strong near. These ventriloqui, therefore, by forming their voice, not as others by the emission of their breath, but by drawing it inwards, do make the same appear small and weak; which weakness of the voice deceives those, that neither suspect the artifice nor observe the endeavour which they use in speaking; and so, instead of thinking it weak, they think it far off.

[Sidenote: Not only air, but other bodies, how hard soever they be,
convey sound.]

10. As for the medium, which conveys sound, it is not air only. For water, or any other body how hard soever, may be that medium. For the motion may be propagated perpetually in any hard continuous body; but by reason of the difficulty, with which the parts of hard bodies are moved, the motion in going out of hard matter makes but a weak impression upon the air. Nevertheless, if one end of a very long and hard beam be stricken, and the ear be applied at the same time to the other end, so that, when the action goeth out of the beam, the air, which it striketh, may immediately be received by the ear, and be carried to the tympanum, the sound will be considerably strong.

In like manner, if in the night, when all other noise which may hinder sound ceaseth, a man lay his ear to the ground, he will hear the sound of the steps of passengers, though at a great distance; because the motion, which by their treading they communicate to the earth, is propagated to the ear by the uppermost parts of the earth which receiveth it from their feet.

[Sidenote: The causes of grave and acute sounds, and of concent.]

11. I have shown above, that the difference between grave and acute sounds consisteth in this, that by how much the shorter the time is, in which the reciprocations of the parts of a body stricken are made, by so much the more acute will be the sound. Now by how much a body of the same bigness is either more heavy or less stretched, by so much the longer will the reciprocations last; and therefore heavier and less stretched bodies, if they be like in all other respects, will yield a graver sound than such as be lighter and more stretched.

As for the concent of sounds, it is to be considered that the reciprocation or vibration of the air, by which sound is made, after it hath reached the drum of the ear, imprinteth a like vibration upon the air that is inclosed within it; by which means the sides of the drum within are stricken alternately. Now the concent of two sounds consists in this, that the tympanum receives its sounding stroke from both the sounding bodies in equal and equally frequent spaces of time; so that when two strings make their vibrations in the same times, the concent they produce is the most exquisite of all other. For the sides of the tympanum, that is to say of the organ of hearing, will be stricken by both those vibrations together at once, on one side or other. For example, if the two equal strings A B and C D be stricken together, and the latitudes of their vibrations E F and G H be also equal, and the points E, G, F and H be in the concave superficies of the tympanum, so that it receive strokes from both the strings together in E and G, and again together in F and H, the sound, which is made by the vibrations of each string, will be so like, that it may be taken for the same sound, and is called _unison_; which is the greatest concord. Again, the string A B retaining still its former vibration E F, let the string C D be stretched till its vibration have double the swiftness it had before, and let E F be divided equally in I. In what time therefore the string C D makes one part of its vibration from G to H, in the same time the string A B will make one part of its vibration from E to I; and in what time the string C D hath made the other part of its vibration back from H to G, in the same time another part of the vibration of the string A B will be made from I to F. But the points F and G are both in the sides of the organ, and therefore they will strike the organ both together, not at every stroke, but at every other stroke. And this is the nearest concord to unison, and makes that sound which is called an _eighth_. Again, the vibration of the string A B remaining still the same it was, let C D be stretched till its vibration be swifter than that of the string A B in the proportion of 3 to 2, and let E F be divided into three equal parts in K and L. In what time therefore the string C D makes one third part of its vibration, which third part is from G to H, the string A B will make one third part of its vibration, that is to say, two-thirds of E F, namely, E L. And in what time the string C D makes another third part of its vibration, namely H G, the string A B will make another third part of its vibration, namely from L to F, and back again from F to L. Lastly, whilst the string C D makes the last third part of its vibration, that is from G to H, the string A B will make the last third part of its vibration from L to E. But the points E and H are both in the sides of the organ. Wherefore, at every third time, the organ will be stricken by the vibration of both the strings together, and make that concord which is called a _fifth_.

A-------B
C-------D
G E
| |
| | K
| |
| | I
| |
| | L
| |
H F

[Sidenote: Phenomena of smelling.]

12. For the finding out the cause of _smells_, I shall make use of the evidence of these following phenomena. First, that smelling is hindered by cold, and helped by heat. Secondly, that when the wind bloweth from the object, the smell is the stronger; and, contrarily, when it bloweth from the sentient towards the object, the weaker; both which phenomena are, by experience, manifestly found to be true in dogs, which follow the track of beasts by the scent. Thirdly, that such bodies, as are less pervious to the fluid medium, yield less smell than such as are more pervious; as may be seen in stones and metals, which, compared with plants and living creatures, and their parts, fruits and excretions, have very little or no smell at all. Fourthly, that such bodies, as are of their own nature odorous, become yet more odorous when they are bruised. Fifthly, that when the breath is stopped, at least in men, nothing can be smelt. Sixthly, that the sense of smelling is also taken away by the stopping of the nostrils, though the mouth be left open.

[Sidenote: The first organ and the generation of smelling.]

13. By the fifth and sixth phenomenon it is manifest, that the first and immediate organ of smelling is the innermost cuticle of the nostrils, and that part of it, which is below the passage common to the nostrils and the palate. For when we draw breath by the nostrils we draw it into the lungs. That breath, therefore, which conveys smells is in the way which passeth to the lungs, that is to say, in that part of the nostrils which is below the passage through which the breath goeth. For, nothing is smelt, neither beyond the passage of the breath within, nor at all without the nostrils.

And seeing that from different smells there must necessarily proceed some mutation in the organ, and all mutation is motion; it is therefore also necessary that, in smelling, the parts of the organ, that is to say of that internal cuticle and the nerves that are inserted into it, must be diversely moved by different smells. And seeing also, that it hath been demonstrated, that nothing can be moved but by a body that is already moved and contiguous; and that there is no other body contiguous to the internal membrane of the nostrils but breath, that is to say attracted air, and such little solid invisible bodies, if there be any such, as are intermingled with the air; it follows necessarily, that the cause of smelling is either the motion of that pure air or ethereal substance, or the motion of those small bodies. But this motion is an effect proceeding from the object of smell, and, therefore, either the whole object itself or its several parts must necessarily be moved. Now, we know that odorous bodies make odour, though their whole bulk be not moved. Wherefore the cause of odour is the motion of the invisible parts of the odorous body. And these invisible parts do either go out of the object, or else, retaining their former situation with the rest of the parts, are moved together with them, that is to say, they have simple and invisible motion. They that say, there goes something out of the odorous body, call it an effluvium; which effluvium is either of the ethereal substance, or of the small bodies that are intermingled with it. But, that all variety of odours should proceed from the effluvia of those small bodies that are intermingled with the ethereal substance, is altogether incredible, for these considerations; first, that certain unguents, though very little in quantity, do nevertheless send forth very strong odours, not only to a great distance of place, but also for a great continuance of time, and are to be smelt in every point both of that place and time; so that the parts issued out are sufficient to fill ten thousand times more space, than the whole odorous body is able to fill; which is impossible. Secondly, that whether that issuing out be with strait or with crooked motion, if the same quantity should flow from any other odorous body with the same motion, it would follow that all odorous bodies would yield the same smell. Thirdly, that seeing those effluvia have great velocity of motion (as is manifest from this, that noisome odours proceeding from caverns are presently smelt at a great distance) it would follow, that, by reason there is nothing to hinder the passage of those effluvia to the organ, such motion alone were sufficient to cause smelling; which is not so; for we cannot smell at all, unless we draw in our breath through our nostrils. Smelling, therefore, is not caused by the effluvium of atoms; nor, for the same reason, is it caused by the effluvium of ethereal substance; for so also we should smell without the drawing in of our breath. Besides, the ethereal substance being the same in all odorous bodies, they would always affect the organ in the same manner; and, consequently, the odours of all things would be alike.

It remains, therefore, that the cause of smelling must consist in the simple motion of the parts of odorous bodies without any efflux or diminution of their whole substance. And by this motion there is propagated to the organ, by the intermediate air, the like motion, but not strong enough to excite sense of itself without the attraction of air by respiration. And this is a possible cause of smelling.

[Sidenote: How smelling is helped by heat and by wind.]

14. The cause why smelling is hindered by cold and helped by heat may be this; that heat, as hath been shown in chapter XXI, generateth simple motion; and therefore also, wheresoever it is already, there it will increase it; and the cause of smelling being increased, the smell itself will also be increased. As for the cause why the wind blowing from the object makes the smell the stronger, it is all one with that for which the attraction of air in respiration doth the same. For, he that draws in the air next to him, draws with it by succession that air in which is the object. Now, this motion of the air is wind, and, when another wind bloweth from the object, will be increased by it.

[Sidenote: Why such bodies are least smelt, which have the least
intermixture of air in them.]

15. That bodies which contain the least quantity of air, as stones and metals, yield less smell than plants and living creatures; the cause may be, that the motion, which causeth smelling, is a motion of the fluid parts only; which parts, if they have any motion from the hard parts in which they are contained, they communicate the same to the open air, by which it is propagated to the organ. Where, therefore, there are no fluid parts as in metals, or where the fluid parts receive no motion from the hard parts, as in stones, which are made hard by accretion, there can be no smell. And therefore also the water, whose parts have little or no motion, yieldeth no smell. But, if the same water, by seeds and the heat of the sun, be together with particles of earth raised into a plant, and be afterwards pressed out again, it will be odorous, as wine from the vine. And as water passing through plants is by the motion of the parts of those plants made an odorous liquor; so also of air, passing through the same plants whilst they are growing, are made odorous airs. And thus also it is with the juices and spirits, which are bred in living creatures.

[Sidenote: Why odorous things become more odorous, when bruised.]

16. That odorous bodies may be made more odorous by contrition proceeds from this, that being broken into many parts, which are all odorous, the air, which by respiration is drawn from the object towards the organ, doth in its passage touch upon all those parts, and receive their motion. Now, the air toucheth the superficies only; and a body having less superficies whilst it is whole, than all its parts together have after it is reduced to powder, it follows that the same odorous body yieldeth less smell whilst it is whole, than it will do after it is broken into smaller parts. And thus much of smells.

[Sidenote: The first organ of tasting; and why some savours cause
nauseousness.]

17. The taste follows; whose generation hath this difference from that of the sight, hearing, and smelling, that by these we have sense of remote objects; whereas, we taste nothing but what is contiguous, and doth immediately touch either the tongue or palate, or both. From whence it is evident, that the cuticles of the tongue and palate, and the nerves inserted into them are the first organ of taste; and (because from the concussion of the parts of these, there followeth necessarily a concussion of the _pia mater_) that the action communicated to these is propagated to the brain, and from thence to the farthest organ, namely, the heart, in whose reaction consisteth the nature of sense.

Now, that savours, as well as odours, do not only move the brain but the stomach also, as is manifest by the loathings that are caused by them both; they, that consider the organ of both these senses, will not wonder at all; seeing the tongue, the palate and the nostrils, have one and the same continued cuticle, derived from the _dura mater_.

And that effluvia have nothing to do in the sense of tasting, is manifest from this, that there is no taste where the organ and the object are not contiguous.

By what variety of motions the different kinds of tastes, which are innumerable, may be distinguished, I know not. I might with others derive them from the divers figures of those atoms, of which whatsoever may be tasted consisteth; or from the diverse motions which I might, by way of supposition, attribute to those atoms; conjecturing, not without some likelihood of truth, that such things as taste sweet have their particles moved with slow circular motion, and their figures spherical; which makes them smooth and pleasing to the organ; that bitter things have circular motion, but vehement, and their figures full of angles, by which they trouble the organ; and that sour things have strait and reciprocal motion, and their figures long and small, so that they cut and wound the organ. And in like manner I might assign for the causes of other tastes such several motions and figures of atoms, as might in probability seem to be the true causes. But this would be to revolt from philosophy to divination.

[Sidenote: The first organ of feeling; and how we came to the knowledge
of such objects as are common to the touch and to other
senses.]

18. By the _touch_, we feel what bodies are cold or hot, though they be distant from us. Others, as hard, soft, rough, and smooth, we cannot feel unless they be contiguous. The organ of touch is every one of those membranes, which being continued from the _pia mater_ are so diffused throughout the whole body, as that no part of it can be pressed, but the _pia mater_ is pressed together with it. Whatsoever therefore presseth it, is felt as hard or soft, that is to say, as more or less hard. And as for the sense of rough, it is nothing else but innumerable perceptions of hard and hard succeeding one another by short intervals both of time and place. For we take notice of rough and smooth, as also of magnitude and figure, not only by the touch, but also by memory. For though some things are touched in one point, yet rough and smooth, like quantity and figure, are not perceived but by the flux of a point, that is to say, we have no sense of them without time; and we can have no sense of time without memory.

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