TABLE OF MATTERS

Contained in this Treatise

[CHAP. I. On Rays Propagated in Straight Lines.]
That Light is produced by a certain movement.[p. 3]
That no substance passes from the luminous object to the eyes.[p. 3]
That Light spreads spherically, almost as Sound does.[p. 4]
Whether Light takes time to spread.[p. 4]
Experience seeming to prove that it passes instantaneously.[p. 5]
Experience proving that it takes time.[p. 8]
How much its speed is greater than that of Sound.[p. 10]
In what the emission of Light differs from that of Sound.[p. 10]
That it is not the same medium which serves for Light and Sound.[p. 11]
How Sound is propagated.[p. 12]
How Light is propagated.[p. 14]
Detailed Remarks on the propagation of Light.[p. 15]
Why Rays are propagated only in straight lines.[p. 20]
How Light coming in different directions can cross itself.[p. 22]
[CHAP. II. On Reflexion.]
Demonstration of equality of angles of incidence and reflexion.[p. 23]
Why the incident and reflected rays are in the same plane perpendicular to the reflecting surface.[p. 25]
That it is not needful for the reflecting surface to be perfectly flat to attain equality of the angles of incidence and reflexion.[p. 27]
[CHAP. III. On Refraction.]
That bodies may be transparent without any substance passing through them.[p. 29]
Proof that the ethereal matter passes through transparent bodies.[p. 30]
How this matter passing through can render them transparent.[p. 31]
That the most solid bodies in appearance are of a very loose texture.[p. 31]
That Light spreads more slowly in water and in glass than in air.[p. 32]
Third hypothesis to explain transparency, and the retardation which Light suffers.[p. 32]
On that which makes bodies opaque.[p. 34]
Demonstration why Refraction obeys the known proportion of Sines.[p. 35]
Why the incident and refracted Rays produce one another reciprocally.[p. 39]
Why Reflexion within a triangular glass prism is suddenly augmented when the Light can no longer penetrate.[p. 40]
That bodies which cause greater Refraction also cause stronger Reflexion.[p. 42]
Demonstration of the Theorem of Mr. Fermat.[p. 43]
[CHAP. IV. On the Refraction of the Air.]
That the emanations of Light in the air are not spherical.[p. 45]
How consequently some objects appear higher than they are.[p. 47]
How the Sun may appear on the Horizon before he has risen.[p. 49]
That the rays of light become curved in the Air of the Atmosphere, and what effects this produces.[p. 50]
[CHAP. V. On the Strange Refraction of Iceland Crystal.]
That this Crystal grows also in other countries.[p. 52]
Who first-wrote about it.[p. 53]
Description of Iceland Crystal; its substance, shape, and properties.[p. 53]
That it has two different Refractions.[p. 54]
That the ray perpendicular to the surface suffers refraction, and that some rays inclined to the surface pass without suffering refraction.[p. 55]
Observation of the refractions in this Crystal.[p. 56]
That there is a Regular and an Irregular Refraction.[p. 57]
The way of measuring the two Refractions of Iceland Crystal.[p. 57]
Remarkable properties of the Irregular Refraction.[p. 60]
Hypothesis to explain the double Refraction.[p. 61]
That Rock Crystal has also a double Refraction.[p. 62]
Hypothesis of emanations of Light, within Iceland Crystal, of spheroidal form, for the Irregular Refraction.[p. 63]
How a perpendicular ray can suffer Refraction.[p. 64]
How the position and form of the spheroidal emanations in this Crystal can be defined.[p. 65]
Explanation of the Irregular Refraction by these spheroidal emanations.[p. 67]
Easy way to find the Irregular Refraction of each incident ray.[p. 70]
Demonstration of the oblique ray which traverses the Crystal without being refracted.[p. 73]
Other irregularities of Refraction explained.[p. 76]
That an object placed beneath the Crystal appears double, in two images of different heights.[p. 81]
Why the apparent heights of one of the images change on changing the position of the eyes above the Crystal.[p. 85]
Of the different sections of this Crystal which produce yet other refractions, and confirm all this Theory.[p. 88]
Particular way of polishing the surfaces after it has been cut.[p. 91]
Surprising phenomenon touching the rays which pass through two separated pieces; the cause of which is not explained.[p. 92]
Probable conjecture on the internal composition of Iceland Crystal, and of what figure its particles are.[p. 95]
Tests to confirm this conjecture.[p. 97]
Calculations which have been supposed in this Chapter.[p. 99]
[CHAP. VI. On the Figures of transparent bodies which serve for Refraction and for Reflexion.]
General and easy rule to find these Figures.[p. 106]
Invention of the Ovals of Mr. Des Cartes for Dioptrics.[p. 109]
How he was able to find these Lines.[p. 114]
Way of finding the surface of a glass for perfect refraction, when the other surface is given.[p. 116]
Remark on what happens to rays refracted at a spherical surface.[p. 123]
Remark on the curved line which is formed by reflexion in a spherical concave mirror.[p. 126]

TREATISE ON LIGHT

CHAPTER I

ON RAYS PROPAGATED IN STRAIGHT LINES