He remarks that it is impossible to suppose that the particles of mastic are in the form of bubbles.
The light scattered from small particles is of a much richer blue than the blue of the first order as reflected from a very thin plate.
Consider the particles which occupy a thin stratum dx perpendicular to the primary ray x.
It is evident that the normal blue is more or less diluted with extraneous white light, having its origin in reflections from the grosser particles of foreign matter with which the air is usually charged.
The same is true in the case of a liquid such as water; it can be divided into drops and these again into smaller drops, or into the finest spray the particles of which are too small to be detected by our unaided vision.
Even with the particles retarding the motion of the aether, the same will be true if, to counterbalance the increased inertia, suitable forces are caused to act on the aether at all points where the inertia is altered.
So long as the precipitated particles are very fine, the light dispersed in a perpendicular direction is sky-blue and fully polarized.
Certain difficulties that he met with in his speculations led him to the conclusion that the particles of any one kind of gas, though all of them alike, must differ from those of another gas both in size and weight.
On account of the smallness of the particles, the forces acting throughout the volume of any individual particle are all of the same intensity and direction, and may be considered as a whole.
The change in the wave-length of the light has the same effect in this respect as a change in the size of the particles, and the comparison gives curious information as to the rate of growth.
Their view was that "matter is not indefinitely divisible, but that all substances are formed of indivisible particles or atoms which are eternal and unchangeable, that the atoms are separated from one another by void, and that these atoms, by their combinations, form the matter we are conscious of."
At a further stage of their growth the particles disperse in the perpendicular direction a light which is no longer fully polarized.
So long as the particles are all very small in comparison with the wave-length, there is complete polarization in the perpendicular direction; but when the size is such that obliquity sets in, the degree of obliquity will vary with the size of the particles, and the polarization will be complete only on the very unlikely condition that the size is the same for them all.
It must not be forgotten, too, that a very moderate increase of dimensions may carry the particles beyond the reach of our approximations.
It is obvious that the aerial particles are illuminated not only by the direct solar rays, but also by light dispersed from other parts of the atmosphere and from the earth's surface.
Dust particles interfere with conduction near the ground, so the relative conductivity in the upper layers may be much greater than that calculated.
It is practically impossible to work with the sensitive film in contact with the reseau-film, not only because dust particles and contact would injure the silver film, but also because the plate-glass used for the photographic plates is seldom a perfect plane.
In both these doctrines of a priori science Descartes has not been subverted, but, if anything, corroborated by the results of experimental physics; for the so-called atoms of chemical theory already presuppose, from the Cartesian point of view, certain aggregations of the primitive particles of matter.
As the movement of one particle in a closely-packed universe is only possible if all other parts move simultaneously, so that the last in the series steps into the place of the first; and as the figure and division of the particles varies in each point in the universe, there will inevitably at the same instant result throughout the universe an innumerable host of more or less circular movements, and of vortices or whirlpools of material particles varying in size and velocity.
As the small filings produced by friction seek to pass through the interstices between the rapidly revolving spherical particles in the vortex, they are detained and become twisted and channelled in their passage, and when they reach the edge of the inner ocean of solar dust they settle upon it as the froth and foam produced by the agitation of water gathers upon its surface.
It banished the spirits and genii, to which even Kepler had assigned the guardianship of the planetary movements; and, if it supposes the globular particles of the envelope to be the active force in carrying the earth round the sun, we may remember that Newton himself assumed an aether for somewhat similar purposes.
In doing what he did, Descartes actually exemplified that reduction of the processes of nature to mere transposition of the particles of matter, which in different ways was a leading idea in the minds of Bacon, Hobbes and Gassendi.
A fire without light, compared to the heat which gathers in a haystack when the hay has been stored before it was properly dry - heat, in short, as an agitation of the particles - is the motive cause of the contraction and dilatations of the heart.
Held between the thumb and fingers of the right hand, they are used as tongs to take up portions of the food, which is brought to table cut up into small and convenient pieces, or as means for sweeping the rice and small particles of food into the mouth from the bowl.
The phenomenon is due to very fine particles of dust suspended in the high regions of the atmosphere that produce a scattering effect upon the component parts of white light.
He showed that the heat motion of particles, which is too small to be perceptible when these particles are large, and which cannot be observed in molecules since these themselves are too small, must be perceptible when the particles are just large enough to be visible and gave complete equations which enable the masses themselves to be deduced from the motions of these particles.
The laws which govern particles of matter in the inorganic world govern them likewise if they are joined into an organism.
If we examine such a substance as sugar we find that it can be broken up into fine grains, and these again into finer, the finest particles still appearing to be of the same nature as sugar.
Moreover, small particles do not seem to exist in the water until it is broken up; so far as we can see, the material of the water is continuous not granular.
The atomist would say, "Yes, it is broken up into its atoms, and these are distributed throughout the spaces between the particles of water."
Following Newton, he believed a gas to be made up of particles or atoms, From Dalton's Hydrogen Gas.
In the first place, with a given size of particles, the direction of complete polarization indicated by (23) is a function of the colour of the light, the value of 0 being 3 or 4 times as large for the violet as for the red end of the spectrum.