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Thus, there is no intrinsic sweetness in
sugar; but the quality of sweetness is in the sense of the palate.
In a violet, there is no inherent colour; but the sense of colour, called violet, is in our optic nerve; and the sense of sweetness produced by the same flower, is in the olfactory nerve.
So, there is no sound in a vibrating string; but the sound, so called, is the vibrating effect produced on our auditory nerves.
And the sense of hardness, or substance in a stone, arises from its being harder than our fingers, which have not power to pass through it.
Obs. It has been a favourite notion of ancient and modern philosophers, that the substratum or basis of all matter is the same; and that all the varieties exhibited to our senses, are only so many modifications, capable of producing their respective sensible effects.
619. A person, born blind, has no sense or conception of colours: he can feel the hardness, the roughness, and the length and breadth of surfaces; but he can have no perception of their various colours.
So, one born deaf, sees the motion of a bow on a violin, or the sticks on a drum; but has no idea of their sound.
In like manner, all food is alike, in flavour, to those who have lost their sense of taste and smell.
620. The sensations produced by things out of ourselves, are called our perceptions; and the property or power of bodies to excite or create particular perceptions, is, in common language, considered as the perception itself; and the body
is considered as possessing the sensation itself, which it only creates in us.
Thus, we call vinegar sour, oil smooth, and fire hot; though the sense of sourness, smoothness, and heat, is in us, not in the bodies which create those perceptions.
So, likewise, in common language, we talk of the motion of the sun and stars; though it is only our earth that moves.
621. Every collection, then, of properties, capable of affecting our senses, is called material, or matter; and it possesses extension, or bulk ; solidity, or the power of maintaining its space; divisibility, or the capability of being divided into infinitely small parts; and a power, or disposition to coalesce or unite with other matters.
Without external force, such matter is inert or dead; but it may be put in motion by powers sufficient to overcome its inertness, or its disposition to unite with larger masses.
So, also, motion, once acquired, would continue for ever, if not checked by opposing powers, or by friction.
The disposition of all matter to rush or fall together, is usually called attraction; and is supposed, by Sir Isaac Newton and others, to arise from effluvia emitted from the respective bodies.
Obs.—This idea has been combated by Sir Richard Phillips, in the Monthly Mag. Oct. 1, 1811. He asks, how any effluvia can take hold of distant bodies; and what connection can exist between such effluvia, and the body whence they flowed, to occasion them to solicit another body, to return with them back to it? He then suggests, that all space is filled with an etherial, elastic medium, except in the points occupied by matter, as the
Sun, Stars, and Planets; that this medium solicits to enter the foreign substances of matter, in degrees proportioned to their density and peculiar construction; that these forces act in right lines infinitely extended from the substance; that the phenomenon of attraction arises from the interception of those infinite lines by other bodies; that the forces must then be FINITE in the direction of any two substances, but INFINITE in other directions; and that, of course, all bodies must fall towards each other in the line which joins their centres; because they are pressed FINITELY in that direction, but INFINITELY in every other. Thus, bodies are pressed to the earth, by forces infinitely extended in their zenith; but the action of those forces in their nadir is taken off, by the interposition of the mass of the earth. So, likewise, the pressure on the earth is always diminished on the side immediately next the sun; while it is infinite on every other side; and that pressure necessarily produces the phenomena called attraction.
622. Extension is infinite ; at least the human mind can set no bounds to it, but can add millions to millions of miles in
direction. Such matter as affects our senses, is, however, not visible every where; but the spaces between the stars and planets are supposed to be filled with a rare, elastic medium.
Solidity is a relative idea; and is measured by us, in the ratio of the attraction to the earth called weight.
A cubic foot of platina weighs as much as 92 cubic feet of cork, or as 230,000 cubic feet of hydrogen gas; yet the platina itself may be light compared with other bodies unknown, and the cork and the gas be heavy in regard to others.
Obs.—The whole earth, in solid matter, might, perhaps, be compressed into the compass of an orange; just as 1000 cubic feet of elastic steam can be re-compressed
into its original foot of water. To suppose any void in creation, is blasphemy against the omnipresent Creator.
623. The property of infinite divisibility will be evident, from the consideration that every particle of matter, however small, must have an upper
and an under side. The power of mutual attraction, or rather, of universal pressure, is proved by the falling of all loose bodies to the ground, in a perpendicular direction, towards the centre of the earth; by the motions of the planetary bodies round the sun; by the combined or curved direction of projected bodies; and by the continually accelerating motion of falling bodies.
Obs. 1.-The infinite divisibility of matter is evident, in the formation of animalculæ, already treated of, and of the malleability of gold. Scents are equally subtile; and it is computed, that the millionth part of a grain of musk, divides itself into seven quadrillions of parts, in scenting a room. So, also, the light generated by a single grain of tallow, diffuses itself over a space two miles round.
2.-Accelerated motion, in falling bodies, is created by new impulses of attraction, or pressure, acting on a body already possessed of a given motion, and which acts at every instant, as though no motion were already acquired. The motion is, as the square of the times employed in falling. Thus,Seconds of time, 1, 2, 3, 4,
5, &c. Their squares,
1, 4, 9, 16, 25, &c. Feet of motion, 20, 80, 180, 320, 500, &c. 3.-Attraction, or pressure, is always in proportion to the quantity of matter in bodies; and it decreases by the same law as surfaces increase, i.e. according to the squares of the distances of the bodies from each other:
4.--Light and heat observe the same law; and decrease according to the square of the distance of the luminous
body: because, as light and heat diverge from a centre, their density on every surface presented to them, will necessarily be as the square of the distance, or radii of the diverging influences or rays.
5.-Kepler ascertained, and Sir Isaac Newton demonstrated, that from the combined forces of attraction and rectilinear motion, the squares of the periodical times or revolutions of the planets are, as the cubes of their distances. Hence, the distance of the earth from the sun being ascertained, and the times of all the planetary revolu ions being known from observation, their several distances are ascertained by a simple rule of proportion.
6.-The following are the conclusions of Sir Richard Phillips, relative to the laws of the planetary motions:
The rotatory motion of a planetary body subject to a uniform external pressure, from a uniformly diffused medium, is a necessary consequence of a peculiar and nicely adjusted disposition of the component parts in regard to their density.
A rotory and centrifugal motion, is a consequence of the lighter parts being fluid, and producing oscillations against the denser parts of corresponding and competent force, varying, at the same time, the centre of motion.
A motion of that centre in a circular orbit, is a consequence of the combined force of the oscillations, with the diminished pressure of the near or inner side of the body in regard to a larger or centrical body, as in the earth and sun.
An elliptical orbit inclined to the plane of the equator of the moving body, is, then, a consequence of the ar. rangement of an excess of the oscillating fluid in one of the hemispheres,-as in our southern hemisphere.
No peculiar numerical laws of pressure in the universal medium, nor any given centrifugal force, are required to effect the motions of the planetary bodies. It is simply necessary, that the powers should be uniform, uni. versal, and in a degree calculated to balance each other under the existing circumstances. Such an accommodation of powers evidently exists, in a peculiar manner, in