Philosophical Letters: or, modest Reflections upon some Opinions in Natural Philosophy. Duchess of Margaret Cavendish Newcastle
then the object is, the cause is the shape and form of the Glass, and not the patterning motions in the Glass. But this discourse belongs properly to the Opticks, wherefore I will leave it to those that are versed in that Art, to enquire and search more after the rational truth thereof. In the mean time, my opinion is, that though the object is the occasion of the figure presented in a Looking-glass, yet the figure is made by the motions of the glass or body that presents it, and that the figure of the glass perhaps may be patterned out as much by the motions of the object in its own substance, as the figure of the object is patterned out and presented by the motions of the glass in its own body or substance. And thus I conclude and rest,
Madam,
Your Faithful Friend
and Servant.
XXVI.
MADAM,
Since I mentioned in my last that Light did disturb the figures of External objects presented in Transparent bodies; you were pleased to ask, Whether light doth penetrate transparent bodies? I answer, for anything I know, it may; for when I consider the subtil, piercing and penetrating nature of light, I believe it doth; but again, when I consider that light is presented to our sight by transparent bodies onely, and not by duskish and dark bodies, and yet that those duskish bodies are more porous then the transparent bodies, so that the light hath more passage to pass through them, then through transparent bodies; but that on the contrary, those dark bodies, as Wood, and the like, do quite obscure the light, when as transparent bodies, as Glass, &c. transmit it, I am half perswaded that the transparent bodies, as Glass, rather present the Light by patterning it out, then by giving it passage: Also I am of a mind, that the air in a room may pattern out the Light from the Glass, for the Light in a room doth not appear so clear as in the Glass; also if the Glass be any way defective, it doth not present the Light so perfectly, whereas, if it were the penetration of light through the glass, the light would pass through all sorts of glass alike, which it doth not, but is more clearly seen through some, and more obscurely through others, according to the goodness or purity of the glass. But you may say, that the light divulges the imperfection or goodness of the glass; I answer, so it doth of any other objects perceived by our sight; for light is the presenter of objects to the sense and perception of sight, and for any thing I know, the corporeal optick motions make the figure of light, the ground figure of all other figures patterned out by the corporeal optick motions, as in dreams, or when as some do see in the dark, that is, without the help of exterior light. But you may say, That if the glass and the air in a room did pattern out the figure of light, those patterns of light would remain when light is absent: I answer, That is not usual in nature; for when the object removes, the Pattern alters; I will not say but that the corporeal optick motions may work by rote without objects, but that is irregular, as in some distempers. And thus, Madam, I have given you my opinion also to this your question; if you have any more scruples, I pray let me know of them, and assure your self that I shall be ready upon all occasions to express my self,
Madam,
Your humble and faithful Servant.
XXVII.
MADAM,
Your desire is to know, why sound is louder in a Vault, and in a large Room then in a less? I answer, A Vault or arched Figure is the freest from obstruction, as being without corners and points, so as the sensitive and rational corporeal motions of the Ear can have a better perception; like as the Eye can see farthest from a hill then being upon a level ground, because the prospect is freer from the hill, as without obstruction, unless it be so cloudy that the clouds do hinder the perception; And as the eye can have a better prospect upon a hill, so the ear a stronger perception in a Vault; And as for sound, that it is better perceived in a large, then in a little close room or place, it is somewhat like the perception of sent, for the more the odorous parts are bruised, the stronger is that perception of sent, as being repeated double or treble, which makes the perception stronger, like as a thick body is stronger then a thin one; So likewise the perception of sound in the air; for though not all the parts of the air make repetitions, yet some or many make patterns of the sound; the truth is, Air is as industrious to divulge or present a sound, by patterns to the Ear, as light doth objects to the Eye. But then you may ask me, Why a long hollow pipe doth convey a voice to the ear more readily, then any large and open place? My answer is, That the Parts of the air in a long pipe are more Composed and not at liberty to wander, so that upon necessity they must move onely to the patterning out of the sound, having no choice, which makes the sound much stronger, and the perception of the Ear perfecter; But as for Pipes, Vaults, Prospects, as also figures presented in a room through a little hole, inverted, and many the like, belongs more to Artists then to my study, for though Natural Philosophy gives or points out the Ground, and shews the reason, yet it is the Artist that Works; Besides it is more proper for Mathematicians to discourse of, which study I am not versed in; and so leaving it to them, I rest,
Madam,
Your faithful Friend
and Servant.
XXVIII.
MADAM,
From Sound I am come to Sent, in the discourse whereof, your Author[1] is pleased to set down these following propositions: 1. That smelling is hindred by cold and helped by heat: 2. That when the Wind bloweth from the object, the smell is the stronger, and when it blows from the sentient towards the object, the weaker, which by experience is found in dogs, that follow the track of beasts by the Sent: 3. That such bodies as are last pervious to the fluid medium, yield less smell then such as are more pervious: 4. That such bodies as are of their own nature odorous, become yet more odorous, when they are bruised: 5. That when the breath is stopped (at least in man) nothing can be smelt: 6. That the Sense of smelling is also taken away by the stopping of the nostrils, though the mouth be left open. To begin from the last, I say, that the nose is like the other sensitive organs, which if they be stopt, the corporeal sensitive motions cannot take copies of the exterior objects, and therefore must alter their action of patterning to some other, for when the eye is shut and cannot perceive outward objects then it works to the Sense of Touch, or on the inside of the organ to some phantasmes; and so do the rest of the Senses. As for the stopping of breath, why it hinders the Sent, the cause is, that the nostrils and the mouth are the chief organs, to receive air and to let out breath: but though they be common passages for air and breath, yet taste is onely made in the mouth and tongue, and sent in the nose; not by the pressure of meat, and the odoriferous object, but by patterning out the several figures or objects of sent and taste, for the nose and the mouth will smell and taste one, nay several things at the same time, like as the eye will see light, colour, and other objects at once, which I think can hardly be done by pressures; and the reason is, that the sensitive motions in the sensitive organs make patterns of several objects at one time, which is the cause, that when flowers, and such like odoriferous bodies are bruised, there are as many figures made as there are parts bruised or divided, and by reason of so many figures the sensitive knowledg is stronger; but that stones, minerals, and the like, seem not so strong to our smell, the reason is, that their parts being close and united, the sensitive motions in the organ cannot so readily perceive and pattern them out, as those bodies which are more porous and divided. But as for the wind blowing the sent either to or from the sentient, it is like a window or door that by the motion of opening and shutting, hinders or disturbeth the sight; for bodies coming between the object and the organ, make a stop of that perception. And as for the Dogs smelling out the track of Beasts, the cause is, that