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 it must be noted that the speed of light in this argument has uhygens assumed such that it takes a time of one hour to make the passage from here to the Moon. And it must be noted that it is special to the plane through GCF and to those which are parallel to it, that all incident rays which are in one of these planes continue to be in it after they have entered the Crystal and have become double; for it is quite otherwise for rays in all other planes which trwatise the Crystal, as we shall see afterwards.

If, in addition, light takes time for its passage—which we are now going to examine—it will follow that this movement, impressed on the intervening matter, is successive; christiaann consequently it spreads, as Sound does, by spherical surfaces and waves: Similarly if the Earth be Treatiwe, and christiazn top of the Atmosphere CD, which 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.

Touching which particles, and their form and disposition, I huygejs, at the end of this Treatise, propound my conjectures and some experiments which confirm them.

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 christiazn 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.

Now it is to be remarked that from the moment when the angle Huuygens is smaller than is requisite to permit the refracted ray DA to pass into the other transparent substance, one finds that the interior reflexion which occurs at the surface AB is much augmented in brightness, as is easy to realize by experiment with a triangular prism; and for this our theory can afford this reason.

Equally so in every reflexion of the light, against whatever body it may be, the angles of reflexion and incidence ought to be equal notwithstanding that the body might be of such a nature that it takes away a portion of the movement made by the tgeatise light. Open Preview See a Problem? Then these lines HF, BG, will bear to one another the said ratio treatide the velocities. Huygens wrote that availability of water in liquid form was essential for life and that the properties christiaaj water must vary from planet to planet to suit the temperature range.


This, however, is quite another thing from being instantaneous, since there is all the difference between a finite thing and an infinite.

Treatise on Light by Christiaan Huygens – Free at Loyal Books

And this suffices to show that the ray will continue along the curved line which intersects all the waves at right angles, as has been said. The pieces of it which are found have the figure of an oblique parallelepiped; each of the six faces being a parallelogram; and it admits of being split in three directions parallel to two of these opposed faces. 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.

If one considers further the other pieces H of the wave AC, it appears that they will not only have reached the surface AB by straight lines HK parallel to CB, but that in addition they will have generated in the transparent air, from the centres K, K, K, particular spherical waves, represented here by circumferences the semi-diameters of which are equal to KM, that is to say to the continuations of HK as far as the line BG parallel to AC.

I’d never before heard of the properties of Icelandic crystal. As to those which can be made here on the Earth, by striking lights at great distances, although they prove that light takes no sensible time to pass over these distances, one may say with good reason that they are too small, and that the only conclusion to be drawn from them is that the passage of light is extremely rapid.

Text was easy to understand but the geometric proofs were less so. It is again a general law in all other transparent bodies that the ray which falls perpendicularly on their surface passes straight on without suffering refraction, and that an oblique ray is always refracted.

Supposing then, in the next figure, as previously, the surface of the crystal g G, the Ellipse GP gand the line N; and CM the refraction of the perpendicular ray FC, from which it diverges by 6 degrees 40 minutes. And I do not believe that this movement can be better explained than by supposing that all those of the luminous bodies which are liquid, such as flames, and apparently the sun and the stars, are composed of particles which float in a much more subtle medium which agitates them with great rapidity, and makes them strike against the particles of the ether which surrounds them, and which are much smaller than they.

Erasmus Bartholinus, who has given a description of Iceland Crystal and of its chief phenomena. Then it must be that the ethereal matter which is inside is not shut up, but flows through it with very great freedom.


It is known that the air which surrounds us, besides the particles which are proper to it and which 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.

Gregory Levine rated it it was ok Aug 02, But the chief foundation, which consists in the remark I have just made, was lacking in his demonstrations; and for the rest he had opinions very different from mine, as may be will appear some day if his writing has been preserved.

Treatise on Light by Christiaan Huygens

And similarly if L be a small hole in a sheet of paper or other substance which is laid against the Crystal, it will appear when turned towards daylight as if there were two holes, which will seem the wider apart from one another the greater the thickness of the Crystal. For all these circles will be enclosed in one another and will all pass beyond the point B. Christiaan Huygens Treatise on Light was published in and is probably the largest scientific volume on light published before Newton’s Opticks.

Zero rated it liked it Jun 17, If you like books and love to build cool products, we may be looking for you. And it must not be thought that in this there is anything absurd or impossible, it being on the contrary quite credible that it is this infinite series of different sizes of corpuscles, having different degrees of velocity, of which Nature makes use to produce so many marvellous effects. You can also preview the book there.

Stephen Simpson rated it really liked it May 20, To which it must further be added in what respect libht bodies differ from those which are opaque; and the more so since it might seem because of the easy penetration of bodies by the ethereal matter, of which mention has been made, trsatise there would not be any body that was not transparent.

It remains then that they are, as has been said, assemblages of particles which touch one another without constituting a continuous solid.

I will say, however, in passing that we may conceive that the particles of the ether, notwithstanding their smallness, are in turn composed of other parts and that their springiness consists in the very rapid movement of a subtle matter which penetrates them from chriatiaan side and constrains their structure to assume such a disposition as to give to this fluid matter the most overt and easy passage possible.

We remark first that each portion of a wave ought to spread in such a way that its extremities lie always between the same straight lines drawn from the luminous point.