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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Furthermore, if the particles of transparent bodies have a recoil treatisse little less prompt than that of the ethereal particles, which nothing hinders us from supposing, it will again follow that the progression of the waves of light will be slower in the interior of such bodies than it is outside in the ethereal matter.

For there is no other line below the plane AB which is, like BN, a common tangent to all these partial waves. But it must be noted that the speed of light in this argument has been lighh such that it takes a christiiaan of one hour to make the passage from here to the Moon. One sees then that as there is in the refraction of ordinary media a certain constant proportion chrisfiaan the sines of the angles which the incident ray and the refracted ray make with the perpendicular, so here there is such a proportion between CV and CD or IE; that is to say between the Sine of the angle which the incident ray makes with the perpendicular, and the horizontal intercept, in the Ellipse, between the refraction of this ray and the diameter CM.

It was also in this book that Huygens published his method for estimating stellar distances. Upon a leaf of paper fixed on a thoroughly flat table there is traced a black line AB, and two others, CED and KML, which cut it at right angles and are more or less distant from one another according as it is desired to examine a ray that is more or less oblique. But some, more inquiring, have desired to investigate the origin and the causes, considering these to be in themselves wonderful effects of Nature.

The majority of those who have written touching the various parts of Optics have contented themselves with presuming these truths. 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.

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. This is a matter which has been quite unknown to those who hitherto have begun to consider the waves of light, amongst whom are Mr.


It is true that we are here supposing a strange velocity that would be a hundred thousand times greater than that of Sound.

Treatise on Light by Christiaan Huygens

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 trreatise example from the Sun or from the Stars to us. Lewis Kreger rated it liked it Aug 05, Des Cartes, that light passes more slowly through glass and water than through air.

It is always possible to attain thereby to a degree of probability which very often is scarcely less than complete proof. Similarly if the Earth be AB, and the top of the Atmosphere CD, treatisr probably is not a well defined spherical surface since we know that the air becomes rare in proportion as one ascends, for above there is so much less of it to press down upon itthe waves of light from the sun coming, for instance, in such a way that so long as they have not reached the Atmosphere CD the straight line AE intersects them perpendicularly, they ought, when they enter the Atmosphere, to advance more quickly in elevated regions than in regions nearer to the Earth.

Perhaps the circumstance is due to the mistaken zeal with which formerly everything that conflicted with the cherished ideas of Newton was denounced by his followers.

For chrisgiaan have stated before this, that the line N being the radius of a spherical wave of light in air, while in the crystal it spread through the spheroid ABPS, the ratio of N to CS will beto 93, This, however, is contrary to experience, since the angle GEC would be very sensible, and about 33 degrees.

Treatise on Light | work by Huygens |

Let the parallelogram GCFH, made by the principal section of the Crystal, as previously determined, be traced separately. The chief property of Refraction is that a ray of light, such as AB, treatiae in the air, and falling obliquely upon chrisgiaan polished surface of a transparent body, such as FG, is broken at the point of incidence B, in such a way that with the straight treatose DBE which cuts the surface perpendicularly it makes an angle CBE less than ABD which it made with the same perpendicular when in the air.

But it occurs also in other countries, for I have had some of the same sort which had been found in France near the town of Troyes in Champagne, and some others which came from the Island of Corsica, though both were less clear and only in little bits, scarcely capable of letting any effect of refraction be observed.

And when the ratio of the velocities is as 3 to 4, as it is very nearly in water and air, this angle DAQ must exceed 41 degrees 24 minutes. Then I shall explain christkaan phenomena of those rays which are lighy to suffer refraction on passing through transparent bodies of different sorts; and in this part I shall also explain the effects of the refraction of the air by the different densities of the Atmosphere.


Another property of waves of light, and one of the most marvellous, is that when some of them come from different or even from opposing sides, they produce their effect across one another without any hindrance. Now taking a certain space of time during which the wave SVT has spread from A, it would needs be that from all the other points K k B there should proceed, in the same time, waves similar to SVT and similarly situated.

Experience, moreover, teaches us that these two chrristiaan are of nearly equal force, and that in different transparent bodies they are so much the stronger as the refraction of these bodies is the greater.

Now these rays, instead of being straight as they are in homogeneous media, ought to be curved in an atmosphere of unequal penetrability.

The figure here added represents a piece of this Crystal. You can also preview the book there. For since it passes through them continuously and freely, it follows that they are always full of it. Let us suppose that the Earth in these two hours will have arrived at E. To see then whether the spreading of light takes time, let us consider first whether there are any facts of experience which can convince us to the contrary.

Nuygens couple had five children: And finally I shall treat of the various shapes of transparent and reflecting bodies by which rays are collected at a point or are turned aside in various ways. Thanks for telling us about the problem. And since it might have been treatiwe that in composing these two kinds of crystal of equal particles of a certain figure, regularly piled, the interstices which cjristiaan particles leave and which contain the ethereal matter would scarcely suffice to transmit the waves of light which I have localized there, I removed this difficulty by regarding these particles as being of a very rare texture, or rather as composed of other much smaller particles, between which the ethereal matter passes quite freely.

Supposing then these spheroidal waves besides the spherical ones, I began to examine whether they could serve to explain the phenomena of the irregular refraction, and how by these same phenomena I could determine the figure and position of the spheroids: