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huygens

huygens

huygens Sentence Examples

  • Huygens, in his Systema saturnium (1659), describes a micrometer with which he determined the apparent diameters of the principal planets.

  • Gascoigne was killed at the battle of Marston Moor on the 2nd of July 1644, in the twenty-fourth year of his age, and his untimely death was doubtless the cause that delayed the publication of a discovery which anticipated, by twenty years, the combined work of Huygens, Malvaison, Auzout and Picard in the same direction.

  • Two Dutch friends, Constantijn Huygens (von Zuylichem), father of the more celebrated Huygens, and Hoogheland, figure amongst the correspondents, not to mention various savants, professors and churchmen (particularly Jesuits).

  • Attempts have been made, principally founded on some remarks of Huygens, to show that Descartes had learned the principles of refraction from the manuscript of a treatise by Willebrord Snell, but the facts are uncertain; and, so far as Descartes founds his optics on any one, it is probably on the researches of Kepler.

  • At the beginning of 1680 he presented a paper to the Royal Society, De nova temporis dimetiendi ratione et accurata horologiorum .constructione, in which he attempted to deprive Huygens of the honour of applying the pendulum to the measurement of time.

  • CHRISTIAAN HUYGENS (1629-1695), Dutch mathematician, mechanician, astronomer and physicist, was born at the Hague on the 14th of April 1629.

  • He was the second son of Sir Constantijn Huygens.

  • Each discovery in turn was, according to the prevailing custom, announced to the learned world under the veil of an anagram - removed, in the case of the first, by the publication, early in 1656, of the little tract De Saturni luna observatio nova; but retained, as regards the second, until 1659, when in the Systema Saturnium the varying appearances of the so-called "triple planet" were clearly explained as the phases of a ring inclined at an angle of 28° to the ecliptic. Huygens was also in 1656 the first effective observer of the Orion nebula; he delineated the bright region still known by his name, and detected the multiple character of its nuclear star.

  • The invention dates from 1656; on the 16th of June 1657 Huygens presented his first "pendulumclock" to the states-general; and the Horologium, containing a description of the requisite mechanism, was published in 1658.

  • Huygens had before this time fixed his abode in France.

  • Although Robert Hooke in 1668 and Ignace Pardies in 1672 had adopted a vibratory hypothesis of light, the conception was a mere floating possibility until Huygens provided it with a sure foundation.

  • This resolution of the original wave is the well-known "Principle of Huygens," and by its means he was enabled to prove the fundamental laws of optics, and to assign the correct construction for the direction of the extraordinary ray in uniaxial crystals.

  • Huygens never married.

  • The publication of a monumental edition of the letters and works of Huygens was undertaken at the Hague by the Societe Hollandaise des Sciences, with the heading ¦uvres de Christian Huygens (1888), &c. Ten quarto volumes, comprising the whole of his correspondence, had already been issued in 1905.

  • A biography of Huygens was prefixed to his Opera varia (1724); his Eloge in the character of a French academician was printed by J.

  • Uylenbroek, Oratio de fratribus Christiano atque Constantino Hugenio (Groningen, 1838); P. Harting, Christiaan Huygens in zijn Leven en Werken geschetzt (Groningen, 1868); J.

  • Sir Constantijn Huygens >>

  • The principle employed in these investigations is due to C. Huygens, and may be thus formulated.

  • Any obscurity that may hang over Huygens's principle is due mainly to the indefiniteness of thought and expression which we must be content to put up with if we wish to avoid pledging ourselves as to the character of the vibrations.

  • We imagine a wave-front divided o x Q into elementary rings or zones - often named after Huygens, but better after Fresnelby spheres described round P (the point at which the aggregate effect is to be estimated), the first sphere, touching the plane at 0, with a radius equal to PO, and the succeeding spheres with radii increasing at each step by IX.

  • Although the matter can be fully treated only upon the basis of a dynamical theory, it is proper to point out at once that there is an element of assumption in the application of Huygens's principle to the calculation of the effects produced by opaque screens of limited extent.

  • whether it was the cutting edge or the back of a razor - made no material difference, and was thus led to the conclusion that the explanation of these phenomena requires nothing more than the application of Huygens's principle to the unobstructed parts of the wave.

  • When, in order to apply Huygens's principle, the wave is supposed to be broken up, the phase is the same at every element of the surface of resolution which lies upon a line perpendicular to the plane of reference, and thus the effect of the whole line, or rather infinitesimal strip, is related in a constant manner to that of the element which lies O in the plane of reference, and may be considered to be represented thereby.

  • These curves attracted much attention and were discussed by John Bernoulli, Leibnitz, Huygens, David Gregory and others.

  • C. Huygens and R.

  • A collection of formulae relating to the circle, for instance, would comprise not only geometrical and trigonometrical formulae, but also approximate formulae, such as Huygens's rule (§ 91), which are the result of advanced analysis.

  • The length of the arc of a circle, for instance, is known if the length of the chord and its distance from the middle point of the arc are known; but it may be more convenient in such a case to use a formula such as Huygens's rule than to obtain a more accurate result by means of trigonometrical tables.

  • For this reason, formulae which will only give approximate results are usually classed together as rules, whether the inaccuracy lies (as in the case of Huygens's rule) in the formula itself, or (as in the case of Simpson's rule) in its application to the data.

  • If we use c 1 to represent the chord of the whole arc, c 2 the chord of half the arc, and c 4 the chord of one quarter of the arc, then corresponding to (i) and (iii) of § 70 or § 79 we have a (8c 2 - c i) and4 5 (256c 4 - 40c2+ci) as approximations to the length of the arc. The first of these is Huygens's rule.

  • The only aether which has survived is that which was invented by Huygens to explain the propagation of light.

  • Now the direction and phase of the light are those of the ray which reaches the eye; and by Fermat's principle, established by Huygens for undulatory motion, the path of a ray is that track along which the disturbance travels in least time, in the restricted sense that any alteration of any short reach of the path will increase the time.

  • xxiv., from which it was copied and reprinted in the Ada Eruditorum (1707), and also in the Memoirs of the Academy of Sciences at Paris; General Laws of Nature and Motion (1705), a work which is commended by Wolfius as illustrating and rendering easy the writings of Galileo and Huygens, and the Principia of Newton; An Institution of Fluxions, containing the First Principles, Operations, and Applications of that admirable Method, as invented by Sir Isaac Newton (1706).

  • C. Huygens, in his De Circuli Magnitudine Inventa, 1654, proved the propositions of Snell, giving at the same time a number of other interesting theorems, for example, two inequalities which may be written as follows 8 - chd B }- 4 chd Bsin a (chd 0-sin >chd 8+3 (chd 0-sin 0).

  • He also gave approximate rectifications of circular arcs after the manner of Huygens; and, what is very notable, he made an ingenious and, according to J.

  • (c) Wren and Huygens further proved that the law of equal action and reaction, already experimentally established by the former, is deducible from the conservation of the velocity of the common centre of gravity, which is the same as the common velocity of the bodies, that is, deducible from the fact that their common centre of gravity does not change its state of motion or rest by the actions of the bodies between themselves; and they further extended the law to bodies, qua elastic.

  • Descartes helped to generalize and establish the notion of the fundamental character of uniform motion in a straight line, but otherwise his speculations did not point in the direc tion of sound progress in dynamics; and the next substantial advance that was made in the principles of the subject was due to Huygens (1629-1695).

  • But Huygens's most important contribution to the subject was his investigation, published in 1673, of the motion of a rigid pendulum of any form.

  • Newton tells us that this agreement led him to adopt the law of the inverse square of the distance about 1665-1666, before Huygens's results as to circular motion had been published.

  • The use of the pendulum clock in its present form appears to date from the construction of such a clock by Huygens in 16J7.

  • Weston (1730); Huygens, Horologium Oscillatorium (1673); Newton, Philosophiae naturalis principia mathematica (1687; translation by A.

  • He was a great mathematician in an age which produced Descartes, Fermat, Huygens, Wallis and Roberval.

  • Solutions were furnished by Wallis, Huygens, Wren and others; and Pascal published his own in the form of letters from Amos Dettonville (his assumed name as challenger) to Pierre de Carcavy.

  • Formerly classified by the ancient Greeks with halos, rainbows, &c., under the general group of "meteors," they came to receive considerable attention at the hands of Descartes, Christiaan Huygens, and Sir Isaac Newton; but the correct explanation of coronae was reserved until the beginning of the 19th century, when Thomas Young applied the theories of the diffraction and interference of light to this phenomenon.

  • of Huygens there is an original copy of a document (dated 17th October 1608) addressed to the states general by Jacob Andrianzoon (the same individual who is called James Metius by Descartes), petitioning for the exclusive right of selling an instrument of his invention by which distant objects.

  • The first powerful telescopes of this construction were made by Huygens, after much labour, in which he was assisted by his brother.

  • Huygens states that he and his brother made object-glasses of 170 and 210 ft.

  • Huygens contrived some ingenious arrangements for directing such telescopes towards any object visible in the heavens - the focal adjustment and centring of the eyepiece being preserved by a braced rod connecting the objectglass and eye-piece.

  • focal length presented to the Royal Society by Huygens, and found that Hadley's reflector "will bear such a charge as to make it magnify the object as many times as the latter with its due charge, and that it represents objects as distinct, though not altogether so clear and bright....

  • Among other writers, Leibnitz and Huygens give testimony which is the more valuable as being critical.

  • Leibnitz speaks of Bacon as " divini ingenii vir," and, like several other German authors, classes him with Campanella; Huygens refers to his " bonnes methodes."

  • It was as an optician that he was first brought into connexion with Huygens and Leibnitz; and an optical Treatise on the .Rainbow, written by him and long supposed to be lost, was discovered and reprinted by Dr Van Vloten in 1862.

  • It was probably at the suggestion of Huygens that he bent his steps towards Spinoza's lodging.

  • Huygens (Descriptio automati planetarii, 1703) uses the simple continued fraction for the purpose of approximation when designing the toothed wheels of his Planetarium.

  • There he entertained the poet Vondel, the scholar Barlaeus, 1 Constantin Huygens, Vossius, Laurens Reael and others.

  • He also received the De Morgan medal from the London Mathematical Society, and the Huygens medal from Leiden.

  • The mechanical properties of the cycloid were investigated by Christiaan Huygens, who proved the curve to be tautochronous.

  • He was, however, intimate with Constantin Huygens, whose political opinions were more nearly in agreement with his own.

  • In a manuscript journal of Huygens is to be found an entry: " 29 Maj.

  • Huygens, in a letter dated the 8th of June 1694, wrote to Leibnitz, " I do not know if you are acquainted with the accident which has happened to the good Mr Newton, namely, that he has had an attack of phrenitis, which lasted eighteen months, and of which they say his friends have cured him by means of remedies, and keeping him shut up."

  • The improvement of telescopes was prosecuted by Christiaan Huygens from 1655, and promptly led to his discoveries of the sixth Saturnian moon, of the true shape of the Saturnian appendages, and of the multiple character of Huygens.

  • 1691), telescopic sights (so-called) by Jean Picard (1620-1682), who simultaneously introduced the astronomical use of pendulumclocks, constructed by Huygens eleven years previously.

  • Maraldi, Jean Picard, Huygens, Olaus Romer and Nicolas de Lacaille.

  • It was further investigated by John Wallis, Christiaan Huygens (who determined the length of any arc in 1657), and Pierre de Fermat (who evaluated the area between the curve and its asymptote in 1661).

  • That this is not a necessary characteristic of light was discovered by Christian Huygens, who found that, whereas a stream of sunlight in traversing a rhomb of spar in any but one direction always gives rise to two streams of equal brightness, each of these emergent streams is divided by a second rhomb into two portions having a relative intensity dependent upon the position with respect to one another of the principal planes of the faces of entry into the rhombs - the planes through the axes of the crystals perpendicular to the refracting surfaces.

  • The phenomenon of polarization observed by Huygens remained an isolated fact for over a century, until Malus in 1808 discovered that polarization can be produced independently of double refraction, and must consequently be something closely connected with the nature of light itself.

  • This result is not, however, conclusive; for an application of Huygens's principle shows that it is a consequence of the rotation of the plane of polarization by an amount proportional to the distance traversed, independently of the state of affairs within the active medium.

  • - Huygens satisfactorily explained the laws of reflection and refraction on the principles of the wave theory, so far as the direction of the waves is concerned, but his explanation gives no account of the intensity and the polarization of the reflected light.

  • Before the close of 1610 the memorable cycle of discoveries begun in the previous year was completed by the observation of the ansated or, as it appeared to Galileo, triple form of Saturn (the ring-formation was first recognized by Christiaan Huygens in 1655), of the phases of Venus, and of the spots upon the sun.

  • In their numerous allusions to the subtle mercury, which the one makes when treating of a means of measuring time by the efflux of the metal, and the other in a treatise on the transit of the planet, we see traces of the school in which they served their first apprenticeship. Huygens, moreover, in his great posthumous work, Cosmotheoros, seu de terris coelestibus, shows himself a more exact observer of astrological symbols than Kircher himself in his Iter exstaticum.

  • Huygens contends that between the inhabitants of different planets there need not be any greater difference than exists between men of different types on the earth.

  • In the same volume are treatises on "Geometric Loci, or Spherical Tangencies," and on the "Rectification of Curves," besides a restoration of "Apollonius's Plane Loci," together with the author's correspondence addressed to Descartes, Pascal, Roberval, Huygens and others.

  • orbiter images are still frustratingly vague and the Huygens images are few in number and cover only a tiny area.

  • The actual calculation follows a similar course to that by which Huygens's conception of the resolution of a wave into components corresponding to the various parts of the wave-front is usually verified (see Diffraction Of Light).

  • Huygens, in his Systema saturnium (1659), describes a micrometer with which he determined the apparent diameters of the principal planets.

  • It is beyond doubt that Huygens independently discovered that an object placed in the common focus of the two lenses of a Kepler telescope appears as distinct and well-defined as the 3 Delambre, Hist.

  • Gascoigne was killed at the battle of Marston Moor on the 2nd of July 1644, in the twenty-fourth year of his age, and his untimely death was doubtless the cause that delayed the publication of a discovery which anticipated, by twenty years, the combined work of Huygens, Malvaison, Auzout and Picard in the same direction.

  • Two Dutch friends, Constantijn Huygens (von Zuylichem), father of the more celebrated Huygens, and Hoogheland, figure amongst the correspondents, not to mention various savants, professors and churchmen (particularly Jesuits).

  • Attempts have been made, principally founded on some remarks of Huygens, to show that Descartes had learned the principles of refraction from the manuscript of a treatise by Willebrord Snell, but the facts are uncertain; and, so far as Descartes founds his optics on any one, it is probably on the researches of Kepler.

  • At the beginning of 1680 he presented a paper to the Royal Society, De nova temporis dimetiendi ratione et accurata horologiorum .constructione, in which he attempted to deprive Huygens of the honour of applying the pendulum to the measurement of time.

  • CHRISTIAAN HUYGENS (1629-1695), Dutch mathematician, mechanician, astronomer and physicist, was born at the Hague on the 14th of April 1629.

  • He was the second son of Sir Constantijn Huygens.

  • But the difficulties interposed by spherical and chromatic aberration had arrested progress in that direction until, in 1655, Huygens, working with his brother Constantijn, hit upon a new method of grinding and polishing lenses.

  • Each discovery in turn was, according to the prevailing custom, announced to the learned world under the veil of an anagram - removed, in the case of the first, by the publication, early in 1656, of the little tract De Saturni luna observatio nova; but retained, as regards the second, until 1659, when in the Systema Saturnium the varying appearances of the so-called "triple planet" were clearly explained as the phases of a ring inclined at an angle of 28° to the ecliptic. Huygens was also in 1656 the first effective observer of the Orion nebula; he delineated the bright region still known by his name, and detected the multiple character of its nuclear star.

  • The invention dates from 1656; on the 16th of June 1657 Huygens presented his first "pendulumclock" to the states-general; and the Horologium, containing a description of the requisite mechanism, was published in 1658.

  • Huygens had before this time fixed his abode in France.

  • The theorems on the composition of forces in circular motion with which it concluded formed the true prelude to Newton's Principia, and would alone suffice to establish the claim of Huygens to the highest rank among mechanical inventors.

  • Although Robert Hooke in 1668 and Ignace Pardies in 1672 had adopted a vibratory hypothesis of light, the conception was a mere floating possibility until Huygens provided it with a sure foundation.

  • This resolution of the original wave is the well-known "Principle of Huygens," and by its means he was enabled to prove the fundamental laws of optics, and to assign the correct construction for the direction of the extraordinary ray in uniaxial crystals.

  • Huygens never married.

  • The publication of a monumental edition of the letters and works of Huygens was undertaken at the Hague by the Societe Hollandaise des Sciences, with the heading ¦uvres de Christian Huygens (1888), &c. Ten quarto volumes, comprising the whole of his correspondence, had already been issued in 1905.

  • A biography of Huygens was prefixed to his Opera varia (1724); his Eloge in the character of a French academician was printed by J.

  • Uylenbroek, Oratio de fratribus Christiano atque Constantino Hugenio (Groningen, 1838); P. Harting, Christiaan Huygens in zijn Leven en Werken geschetzt (Groningen, 1868); J.

  • Sir Constantijn Huygens >>

  • The principle employed in these investigations is due to C. Huygens, and may be thus formulated.

  • Any obscurity that may hang over Huygens's principle is due mainly to the indefiniteness of thought and expression which we must be content to put up with if we wish to avoid pledging ourselves as to the character of the vibrations.

  • We imagine a wave-front divided o x Q into elementary rings or zones - often named after Huygens, but better after Fresnelby spheres described round P (the point at which the aggregate effect is to be estimated), the first sphere, touching the plane at 0, with a radius equal to PO, and the succeeding spheres with radii increasing at each step by IX.

  • Although the matter can be fully treated only upon the basis of a dynamical theory, it is proper to point out at once that there is an element of assumption in the application of Huygens's principle to the calculation of the effects produced by opaque screens of limited extent.

  • whether it was the cutting edge or the back of a razor - made no material difference, and was thus led to the conclusion that the explanation of these phenomena requires nothing more than the application of Huygens's principle to the unobstructed parts of the wave.

  • When, in order to apply Huygens's principle, the wave is supposed to be broken up, the phase is the same at every element of the surface of resolution which lies upon a line perpendicular to the plane of reference, and thus the effect of the whole line, or rather infinitesimal strip, is related in a constant manner to that of the element which lies O in the plane of reference, and may be considered to be represented thereby.

  • These curves attracted much attention and were discussed by John Bernoulli, Leibnitz, Huygens, David Gregory and others.

  • C. Huygens and R.

  • A collection of formulae relating to the circle, for instance, would comprise not only geometrical and trigonometrical formulae, but also approximate formulae, such as Huygens's rule (§ 91), which are the result of advanced analysis.

  • The length of the arc of a circle, for instance, is known if the length of the chord and its distance from the middle point of the arc are known; but it may be more convenient in such a case to use a formula such as Huygens's rule than to obtain a more accurate result by means of trigonometrical tables.

  • For this reason, formulae which will only give approximate results are usually classed together as rules, whether the inaccuracy lies (as in the case of Huygens's rule) in the formula itself, or (as in the case of Simpson's rule) in its application to the data.

  • If we use c 1 to represent the chord of the whole arc, c 2 the chord of half the arc, and c 4 the chord of one quarter of the arc, then corresponding to (i) and (iii) of § 70 or § 79 we have a (8c 2 - c i) and4 5 (256c 4 - 40c2+ci) as approximations to the length of the arc. The first of these is Huygens's rule.

  • The only aether which has survived is that which was invented by Huygens to explain the propagation of light.

  • Now the direction and phase of the light are those of the ray which reaches the eye; and by Fermat's principle, established by Huygens for undulatory motion, the path of a ray is that track along which the disturbance travels in least time, in the restricted sense that any alteration of any short reach of the path will increase the time.

  • xxiv., from which it was copied and reprinted in the Ada Eruditorum (1707), and also in the Memoirs of the Academy of Sciences at Paris; General Laws of Nature and Motion (1705), a work which is commended by Wolfius as illustrating and rendering easy the writings of Galileo and Huygens, and the Principia of Newton; An Institution of Fluxions, containing the First Principles, Operations, and Applications of that admirable Method, as invented by Sir Isaac Newton (1706).

  • C. Huygens, in his De Circuli Magnitudine Inventa, 1654, proved the propositions of Snell, giving at the same time a number of other interesting theorems, for example, two inequalities which may be written as follows 8 - chd B }- 4 chd Bsin a (chd 0-sin >chd 8+3 (chd 0-sin 0).

  • He also gave approximate rectifications of circular arcs after the manner of Huygens; and, what is very notable, he made an ingenious and, according to J.

  • (c) Wren and Huygens further proved that the law of equal action and reaction, already experimentally established by the former, is deducible from the conservation of the velocity of the common centre of gravity, which is the same as the common velocity of the bodies, that is, deducible from the fact that their common centre of gravity does not change its state of motion or rest by the actions of the bodies between themselves; and they further extended the law to bodies, qua elastic.

  • Descartes helped to generalize and establish the notion of the fundamental character of uniform motion in a straight line, but otherwise his speculations did not point in the direc tion of sound progress in dynamics; and the next substantial advance that was made in the principles of the subject was due to Huygens (1629-1695).

  • But Huygens's most important contribution to the subject was his investigation, published in 1673, of the motion of a rigid pendulum of any form.

  • Newton tells us that this agreement led him to adopt the law of the inverse square of the distance about 1665-1666, before Huygens's results as to circular motion had been published.

  • The use of the pendulum clock in its present form appears to date from the construction of such a clock by Huygens in 16J7.

  • Weston (1730); Huygens, Horologium Oscillatorium (1673); Newton, Philosophiae naturalis principia mathematica (1687; translation by A.

  • He was a great mathematician in an age which produced Descartes, Fermat, Huygens, Wallis and Roberval.

  • Solutions were furnished by Wallis, Huygens, Wren and others; and Pascal published his own in the form of letters from Amos Dettonville (his assumed name as challenger) to Pierre de Carcavy.

  • Formerly classified by the ancient Greeks with halos, rainbows, &c., under the general group of "meteors," they came to receive considerable attention at the hands of Descartes, Christiaan Huygens, and Sir Isaac Newton; but the correct explanation of coronae was reserved until the beginning of the 19th century, when Thomas Young applied the theories of the diffraction and interference of light to this phenomenon.

  • of Huygens there is an original copy of a document (dated 17th October 1608) addressed to the states general by Jacob Andrianzoon (the same individual who is called James Metius by Descartes), petitioning for the exclusive right of selling an instrument of his invention by which distant objects.

  • The first powerful telescopes of this construction were made by Huygens, after much labour, in which he was assisted by his brother.

  • Huygens states that he and his brother made object-glasses of 170 and 210 ft.

  • Huygens contrived some ingenious arrangements for directing such telescopes towards any object visible in the heavens - the focal adjustment and centring of the eyepiece being preserved by a braced rod connecting the objectglass and eye-piece.

  • focal length presented to the Royal Society by Huygens, and found that Hadley's reflector "will bear such a charge as to make it magnify the object as many times as the latter with its due charge, and that it represents objects as distinct, though not altogether so clear and bright....

  • Among other writers, Leibnitz and Huygens give testimony which is the more valuable as being critical.

  • Leibnitz speaks of Bacon as " divini ingenii vir," and, like several other German authors, classes him with Campanella; Huygens refers to his " bonnes methodes."

  • It was as an optician that he was first brought into connexion with Huygens and Leibnitz; and an optical Treatise on the .Rainbow, written by him and long supposed to be lost, was discovered and reprinted by Dr Van Vloten in 1862.

  • It was probably at the suggestion of Huygens that he bent his steps towards Spinoza's lodging.

  • Huygens (Descriptio automati planetarii, 1703) uses the simple continued fraction for the purpose of approximation when designing the toothed wheels of his Planetarium.

  • There he entertained the poet Vondel, the scholar Barlaeus, 1 Constantin Huygens, Vossius, Laurens Reael and others.

  • He also received the De Morgan medal from the London Mathematical Society, and the Huygens medal from Leiden.

  • The mechanical properties of the cycloid were investigated by Christiaan Huygens, who proved the curve to be tautochronous.

  • He was, however, intimate with Constantin Huygens, whose political opinions were more nearly in agreement with his own.

  • In a manuscript journal of Huygens is to be found an entry: " 29 Maj.

  • Huygens, in a letter dated the 8th of June 1694, wrote to Leibnitz, " I do not know if you are acquainted with the accident which has happened to the good Mr Newton, namely, that he has had an attack of phrenitis, which lasted eighteen months, and of which they say his friends have cured him by means of remedies, and keeping him shut up."

  • The improvement of telescopes was prosecuted by Christiaan Huygens from 1655, and promptly led to his discoveries of the sixth Saturnian moon, of the true shape of the Saturnian appendages, and of the multiple character of Huygens.

  • 1691), telescopic sights (so-called) by Jean Picard (1620-1682), who simultaneously introduced the astronomical use of pendulumclocks, constructed by Huygens eleven years previously.

  • Maraldi, Jean Picard, Huygens, Olaus Romer and Nicolas de Lacaille.

  • It was further investigated by John Wallis, Christiaan Huygens (who determined the length of any arc in 1657), and Pierre de Fermat (who evaluated the area between the curve and its asymptote in 1661).

  • That this is not a necessary characteristic of light was discovered by Christian Huygens, who found that, whereas a stream of sunlight in traversing a rhomb of spar in any but one direction always gives rise to two streams of equal brightness, each of these emergent streams is divided by a second rhomb into two portions having a relative intensity dependent upon the position with respect to one another of the principal planes of the faces of entry into the rhombs - the planes through the axes of the crystals perpendicular to the refracting surfaces.

  • The phenomenon of polarization observed by Huygens remained an isolated fact for over a century, until Malus in 1808 discovered that polarization can be produced independently of double refraction, and must consequently be something closely connected with the nature of light itself.

  • This result is not, however, conclusive; for an application of Huygens's principle shows that it is a consequence of the rotation of the plane of polarization by an amount proportional to the distance traversed, independently of the state of affairs within the active medium.

  • - Huygens satisfactorily explained the laws of reflection and refraction on the principles of the wave theory, so far as the direction of the waves is concerned, but his explanation gives no account of the intensity and the polarization of the reflected light.

  • Before the close of 1610 the memorable cycle of discoveries begun in the previous year was completed by the observation of the ansated or, as it appeared to Galileo, triple form of Saturn (the ring-formation was first recognized by Christiaan Huygens in 1655), of the phases of Venus, and of the spots upon the sun.

  • He continued his scientific correspondence with unbroken interest and undiminished logical acumen; he thought out the application of the pendulum to the regulation of clockwork, which Huygens successfully realized fifteen years later; and he was engaged in dictating to his disciples, Viviani and Torricelli, his latest ideas on the theory of impact when he was seized with the slow fever which in two months brought him to the grave.

  • In their numerous allusions to the subtle mercury, which the one makes when treating of a means of measuring time by the efflux of the metal, and the other in a treatise on the transit of the planet, we see traces of the school in which they served their first apprenticeship. Huygens, moreover, in his great posthumous work, Cosmotheoros, seu de terris coelestibus, shows himself a more exact observer of astrological symbols than Kircher himself in his Iter exstaticum.

  • Huygens contends that between the inhabitants of different planets there need not be any greater difference than exists between men of different types on the earth.

  • According to Huygens's principle (see Diffraction) each aether particle, set vibrating by an incident wave, can itself act as a new centre of excitement, emitting a spherical wave; and similarly each particle on this wave itself produces wave systems. All systems which are emitted from a single source can by a suitable optical device be directed that they simultaneously influence one and the same aether particle.

  • In the same volume are treatises on "Geometric Loci, or Spherical Tangencies," and on the "Rectification of Curves," besides a restoration of "Apollonius's Plane Loci," together with the author's correspondence addressed to Descartes, Pascal, Roberval, Huygens and others.

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