Donor challenge: Your generous donation will be matched 2-to-1 right now. Your $5 becomes $15! Dear Internet Archive Supporter,. I ask only once a year. The Treatise on Light of Huygens has, however, withstood the test of time: and even now the exquisite skill with which he applied his. Treatise on Light In which are explained the causes of that which occurs in Christiaan Huygens. translated by Silvanus P. Thompson.

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It is known that the air which surrounds us, besides the particles which are proper to it and treafise float in the ethereal matter as has been explained, is full also of particles of water which are raised by the action of heat; and it has been ascertained further by some very definite experiments that as one mounts up higher the density of air diminishes in proportion.

And if chtistiaan contrary movements happen to meet ligth another at the middle sphere, B, or at some other such as C, that sphere will yield and act as a spring at both ilght, and so will serve at the same instant to transmit these two movements. For a visible ray of light, however narrow it may be, has always some width, and consequently it is necessary, in representing the wave whose progression constitutes the ray, to put instead of a line AC some plane figure such as the circle HC in the following figure, by supposing, as we have done, the luminous point to be infinitely distant.

Let a piece be covered with water for llght day or more, the surface loses its natural polish. Now this double refraction, according to my Theory hereinbefore established, seemed to demand a double emission of waves of light, both of them spherical for both the refractions are regular and those of one series a little slower only than the others.

For by the same reasoning about the hollow sphere which I have employed to prove the smallness of the density of glass and its easy penetrability by the ethereal matter, one might also prove that the same penetrability obtains for metals and for every other sort of body.

He is known particularly as an astronomer, physicist, probabilist and horologist. Christiaan Huygens Christiaaj on Light was published in and is probably the largest scientific volume on light published before Newton’s Opticks. Huygens was educated at home until christiazn sixteen years old. But in doing this of which I speak, care must be taken to place the sounding body on cotton or on feathers, in such a way that it cannot communicate its tremors either to the glass vessel which encloses it, or to the machine; a precaution which has hitherto been neglected.

It appears also that the wave BN becomes so much the smaller as the angle CBA or DAQ is made teeatise until when the latter is diminished to the limit indicated a little previously, this wave BN is collected together always at one point.

Now according to our computation, which is given in the Christisan on the causes of the phenomena of Saturn, the distance BA between the Earth and the Sun is about twelve thousand diameters of the Chrjstiaan, and hence four hundred times greater than BC the distance of the Moon, which is 30 diameters. Further, when one considers the extreme speed with which light spreads on every side, and how, when it comes from different regions, even from those directly opposite, the rays traverse one another without hindrance, one may well understand that when we see a luminous object, it cannot be by ilght transport of matter coming to us from this object, in the way in which a shot or an arrow traverses the air; for assuredly that would too greatly impugn these two properties of light, especially the second of them.


Treatise on Light (Illustrated Edition)

hiygens But, for the present, without yet deciding one or other, we will consider these spheroids only in those sections of them which make ellipses in the plane of this figure. This being so, it necessarily follows that every line intersecting one of these waves at right angles will pass above the point A, always excepting the one line which is perpendicular to the horizon. But to demonstrate this curvature of the rays conformably to all our preceding Theory, let us imagine that AB is chridtiaan small portion of a wave of light coming from the side C, which we may consider as a straight line.

And it is evident that when the matter is not homogeneous, but of such a constitution huygeens the movement is communicated in it more rapidly toward one side than toward another, these waves cannot be spherical: But the time along AK is longer than that along AL: In it he speculated on the existence of extraterrestrial life, on other planets, which he imagined was similar to that on Earth. Now, however small we make the opening BG, there is always the same reason causing the light there to pass between straight lines; since this opening is always large enough to contain a great number of particles of the ethereal matter, which are of an inconceivable smallness; so that it appears that each little portion of the wave necessarily advances following the straight line which comes from the luminous point.

This ratio is, in glass, very nearly as 3 to 2; and in water very nearly as 4 to 3; and is likewise different in other diaphanous bodies.

Treatise on Light | work by Huygens |

Now in this same space of time the portion A of the same wave, which has been hindered from communicating its movement beyond the plane AB, or at least partly so, ought to have continued its movement in the matter which is above this plane, and this along a distance equal to CB, making its own partial spherical wave, according to what has been said above.

And experiment shows that in fact there is no polished body the reflexion of which does not follow this rule. Now in quantities of observations of these Eclipses, made during ten consecutive years, these differences have been found to be very considerable, such as ten minutes and more; and from them it has been concluded that in order to traverse the whole diameter of the annual orbit KL, which is double the distance from here to the sun, Light requires about 22 minutes of time.

For the smallness of the particles of quicksilver, for example, being such that one must conceive millions of them, in the smallest visible surface proposed, arranged like a heap of grains of sand which has been flattened as much as it is capable of being, this surface then becomes for our purpose as even as a polished glass is: Vishal rated it it was amazing Jul 02, For the surface consisting thus of particles put together, and the ethereal particles being above, and smaller, it is evident that one could not demonstrate the equality of the angles of incidence and reflexion by similitude to that which happens to a ball thrown against a wall, of which writers have always made use.


For, the point H having been found and marked, as aforesaid, directly above the point E, I observed the appearance of the line CD, which is made by the extraordinary refraction; and having placed the eye at Q, so that this appearance made a straight line with the line KL viewed without refraction, I ascertained the triangles REH, RES, and consequently the angles RSH, RES, which the incident and the refracted ray make with the perpendicular.

Daniel rated it really liked it Nov 15, One sees here not only that our air, which does not penetrate through glass, is the matter by which Sound spreads; but also that it is not the same air but another kind of matter in which Light spreads; since if the air is removed from the vessel the Light does not cease to traverse it as before.

Dianna Caley rated it really liked it Aug 07, She died inshortly after the birth of Huygens’ sister.

I have also stated in the preceding demonstration that the movement of the piece A of the incident wave is not able to communicate itself beyond the plane AB, or at least not wholly. Such are that the rays of light are propagated in straight lines; that the angles of reflexion and of incidence are equal; and that in refraction the ray is bent according to the law of sines, now so well known, and which is no less certain than the preceding laws. For Sound, according to what I have observed, travels about Toises in the time of one Second, or in about one beat of the pulse.

But that which I employed only as a hypothesis, has recently received great seemingness as an established truth by the ingenious proof of Mr.

Although then there are, according to what we have supposed, two different propagations of light within the crystal, it appears that it is only in directions perpendicular to the axis BS of the spheroid that one of these propagations llight more rapidly than the other; but that they have an equal velocity in the other direction, namely, in that parallel to the same axis BS, which is also the axis of the obtuse angle of the crystal.

The piece C, then, of the wave AC, will in a certain space of time have advanced as far as the plane AB following the straight line CB, which may be imagined as coming from the luminous centre, and christiqan consequently will cut AC at right angles. huyfens

In all other transparent bodies that we know there is but one sole and simple refraction; but in this substance there are two different ones.