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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But what may at first appear full strange and even incredible is that the undulations produced by such small movements and corpuscles, should spread to such immense distances; as for example from the Sun or from the Stars to us.

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There are no illustrations or indexes. Bartholinus believed, since that inclination is only 70 degrees 57 minutes, as was stated above. Books by Christiaan Huygens. Kodi rated it liked it Oct 02, Ankit Mathur rated it really liked it Mar 21, Dallas rated it it was ok Jun 04, Hence it appears that the time along ABC is the shortest possible; which was to be proven. Now as we have found CI the refraction of the ray RC, similarly one will find C i the refraction of the ray r C, which comes from the opposite side, by making C o perpendicular to r C and following out the rest of the construction as before.

If one supposes that for this it requires only one minute of time, then it is manifest that the angle CEG will only be 33 minutes; and if it requires only ten seconds of time, the angle will be less than six minutes. And so it may occur that when it ought not to be visible in the absence of vapours, because the line AE encounters the rotundity of the Earth, it will be perceived in the line AF by refraction.

But all these circumferences have as a common tangent the straight line BN, namely the same which is drawn from B as a tangent to the first of the circles, of which A is the centre, and AN the semi-diameter equal to BC, as is easy to see.

Now if one covers the surface AB, leaving there only a small aperture at the point K, situated in the straight line CG, and if one exposes it to the sun, so that his rays face it perpendicularly above, then the ray IK will divide itself at the point K into two, one of which will continue to go on straight by KL, and the other will separate itself along the straight line KM, which is in the plane GCFH, and which makes with KL an angle of about 6 degrees 40 minutes, tending from the side of the solid angle C; and on emerging from the other side of the Crystal it will turn again parallel to JK, along MZ.

Just a moment while we sign you in to your Goodreads account. As to this it is to be remarked that there is a law of motion serving for this propagation, and verifiable by experiment. Then it must be that the ethereal matter which is inside is not shut up, but flows through it with very great freedom. And, first, it follows from what has been said on the production of Light, that each little region of a luminous body, such as the Sun, a candle, or a burning coal, generates its own waves of which that region is the centre.

But each of these waves can be infinitely feeble only as compared with the wave DCF, to the composition of which all the others contribute by the part of their surface which is most distant from the centre A. For there is no other line below the plane AB which is, like BN, a common tangent to all these partial waves.


That is to say that if the ray AB in entering the transparent body is refracted into BC, then likewise CB being taken as a ray in the interior of this body will be refracted, on passing out, into BA. 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. For it is true that inequality will cause a particle by pushing against another larger one to strive to recoil with a part of its movement; but it will thereby merely generate backwards towards the luminous point some partial waves incapable of causing light, and not a wave compounded of many as CE was.

From this it will be seen with what facility, following our new Theory, we find not only the Ellipses, Hyperbolas, and other curves which Mr. Now in applying this kind of movement to that which produces Light there is nothing to hinder us from estimating the particles of the ether to be of a substance as nearly approaching to perfect hardness and possessing a springiness as prompt as we choose. And thus the incident ray DA does not then pierce the surface AB.

Vishal rated it it was amazing Jul 02, Des Cartes gives for the spring, though I do not, like him, suppose the pores to be in the form of round hollow canals. The agitation, moreover, of the particles which engender the light ought to be much more prompt and more rapid than is that of the bodies which cause sound, since we do not see that the tremors of a body which is giving out a sound are capable of giving rise to Light, even as the movement of the hand in the air is not capable of producing Sound.

This comes about from the property of bodies which act as springs, of which we have spoken above; namely that whether compressed little or much they recoil in equal times. Wherefore, according to that which has been explained, BN is the propagation of the wave AC at the moment when the piece C of it has arrived at B.

Before doing so, I will indicate the third and last mode in which transparency may be conceived; which is huygnes supposing that the movement of the waves of light is transmitted indifferently both in the particles of the ethereal matter which occupy the interstices of bodies, and in the particles which compose them, so that the movement passes from one to the other.

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 any 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 christiaaan them.

Let BC be the wave which lighf the light to the spectator who is at B, and let BD be the straight line which intersects this wave at right angles. It is then in some other way that light spreads; and that which can lead us to comprehend it is the knowledge which we have of the spreading of Sound in the air. Perhaps the circumstance chhristiaan due to the mistaken zeal with which formerly everything that conflicted with the cherished ideas of Newton was denounced by his followers.


It is true that we are here supposing a strange velocity that would be a hundred thousand times greater than that of Sound. Christiaan Huygens Treatise on Light was published in and is probably the largest scientific volume on light published before Newton’s Opticks. The proportion of the refraction being what we have just seen, I will now show that there necessarily follows thence that notable property of the ray which falling obliquely on the surface of the crystal enters it without suffering refraction.

For although the particular waves produced by the particles comprised within the space CAE spread also outside this space, they yet do not concur at the same instant to compose a wave which terminates the movement, as they do precisely at the circumference CE, which is their common tangent. Christiaan was named after his paternal grandfather.

The demonstration of this is, it will be seen, entirely similar to that of which we made use in explaining ordinary refraction. The work, translated into English in its year of publication, has been seen as in the fanciful tradition of Francis Godwin, John Wilkins and Cyrano de Bergerac, and fundamentally Utopian; and also to treaatise in its concept of planet to cosmography in the sense of Peter Heylin.

Treatise on Light, by Christiaan Huygens

If then it were enclosed in the sphere in such a way that it could not get out through the pores of the glass, it would be obliged to follow the movement of the sphere when one changes its place: Considering after this the plane of one of these three sections, namely that through GCF, the angle of which is degrees 3 minutes, since the angle F was in above to be 70 degrees 57 minutes; and, imagining a spheroidal wave about the centre C, I knew, because I have just explained it, that its axis must be in the same plane, the half of which axis I have marked CS in the next figure: Want to Read saving….

For since it passes through them continuously and freely, it follows that they are always full of it. And hence one sees the reason why light, at least if its rays are not reflected or broken, spreads only by straight lines, so that it illuminates no object except when the path from its source to that object is open along such lines. 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.

And, therefore, the time of the light along Chriwtiaan, supposing that the ray had been OF, would be equal to the time along BG in the interior of the medium C.

Treatise On Light

So it arises that around each particle there is made a wave of which that particle is the centre. I attributed to this emanation of waves the regular refraction which is observed in this stone, by supposing these waves to be ordinarily of spherical form, and having a slower progression within the Crystal than they have outside it; whence proceeds refraction as I have demonstrated.

This, however, is contrary to experience, since the angle GEC would be very sensible, and about 33 degrees. It is inconceivable to doubt that light consists in the motion of some sort of matter. In our way, on the other hand, the thing is explained without difficulty.

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