FRESNKU AUGUSTIN JKAN. 



FHISI, PAOLO. 



1040 



The phenomena of the colour* exhibited by crystallised plate* when 

 exposed to polarised li^ht, and the ringi which appear to lurround 

 their axes, were attentively examined by Fresnel, and, to conjunction 

 with hi* friend Arago, he iticceeded in reducing the interference* of 

 polarised light to a few simple law*, which were duly verified by 

 experimental analysis. Thi* subject, which had aUo been investigated 

 by Sir David Brewster, 1C. Biot, and subsequently by M. Hitwherlioh, 

 in treated by Frosnel in a Ifdmoire which was read to the Institute of 

 France in 1816. He save formula for the intensity of a previously 

 polarised ray when reflected from a surface under any angle of inci- 

 dence in a plane inclined to the plane of primitive polarisation ; and 

 this, with a general account of the deviations which the plane of 

 polari*ation undergoes in consequence of the reflexion, is coutuined in 

 two Memoir.* which were presented to the Acadi-iuio dei Science* in 

 1*17 and 1818. 



In 1810 he gained the prize which in the preceding year had been 

 proposal by the Institute for the best memoir on the diffraction of 

 light. In hU Memoire he showed that rays passing at a sensible 

 distance from a reflectin,' body deviate from their primitive direc- 

 tion and interfere with the direct rays; and, on the principle* of 

 the undulatory theory, he ascribed the effect to a number of small 

 waves which originate with each portion of the surface of the primitive 

 wave when it arrives at the reflecting surface. In his ' Memoire sur la 

 Diffraction de la Lumicre,' 4to, Paris, Fresnel has given a complete 

 explanation, on the undulatory hypothesis, of the coloured fringes 

 produced by an opaque object when exposed to a luminous point : he 

 ha* also given a table of the several maxima and minima of the 

 intensity of light beyond the limits of the geometrical shadow, and he 

 determined that, within those limits, the light gradually diminishes 

 till total darkness takes place. In order to examine the effects pro- 

 duced by the diffraction of light when it is mode to pass through a 

 mall aperture, he caused the image of the sun at the focus of a glass 

 Ion* to fall precisely at the spot where a small circular orifice was 

 made in a plate of metal ; and, placing before his eye another gloss 

 lens, he (offered the cone of light from the orifice to fall on the Tens, 

 when the image of the orifice appeared as a bright spot, surrounded by 

 ring* of light of different colour*. With a micrometer Fresnel 

 measured the diameter* of these rings, and he has given an explana- 

 tion of the variations produced in the intensity of the light of the 

 central spot when the distance of the eye-glass from the orifice is 

 varied. He observed also the succession of bright and dork bands 

 which are produced when light from a radiant point is reflected from 

 two plane mirrors inclined to one another at an angle nearly equal to 

 180 degree.. 



In a paper entitled 'Considerations theoriques sur la Polarisation 

 de la Lumiere,' which is printed in the ' Bulletin de la Soi-ii'tu 1'hilo- 

 roathiqur,' 1S24, Fresnel assumes that the eye is affected only by those 

 vibratory motions of the particle* of ether which take place trans- 

 versely, or in plane* perpendicular to the direction of the motion of 

 the wave. Unpolarised light he conceived to consUt of a rapid suc- 

 cession of wave* in which the vibration* are performed in every 

 direction perpendicularly to that of the ray ; and common polarised 

 light to consist in the transverse vibrations being parallel to one 

 plane passing through the direction of the ray. J!y combining the 

 hypothesis of transverse vibrations with the theory of undulations, 

 Fresnel obtained formula for the intensity of reflected light at any 

 angle of incidence. 



lie conceived that the phenomena of double refraction in crystals 

 with one axis depend upon a modification of the actions of the other 

 by the action of the molecules of the crystal ; the elasticity of the 

 latter molecule* in a direction perpendicular to the axis being sup- 

 posed to be different from the elasticity in a direction parallel to the 

 axis. In the year 1821 Freanel presented to the Academic de* 

 Sciences a Mrmoire in which the properties of double refraction and 

 polarisation in biaxal crystal* were contemplated; and he investigated 

 what he called the " surface of elasticity ; " a superficies conceived to 

 be such that the force of elasticity by which the vibrations of a mole- 

 cule in the direction of the radius of such surface are regulated in 

 proportional to the square of that radius. He also gave, for doubly 

 refracting crystals with two axes, an indication of the general equation 

 to a wave surface, which ha* liuce been investigated by Ampere and 

 Ms\ccallagn* 



PrnaeVs inquiries were also directed to the subject of rotatory 

 poUrimtion ; and he found by experiments that the phenomena might 

 be explained by conceiving the molecules of ether, which give rise to 

 the rays in the direction of the axis of the quartz, or of tho fluid* in 

 which the like phenomena are exhibited, to revolve uniformly in 

 circles, with different velocities, some from right to left, and other* 

 in a contrary direction. The colours produced by such media he 

 conceived to be owinx to the interference* of two ray* or pencils in 

 which the molecules revolve in opposite directions. 



Kmsnel also proved that light was circularly polarised by two total 

 reflections from glass at an angle equal to about 54 87'; and 

 placing a crystallised plate between two rhomboids of glass, each of 

 which polarised tie light circularly, and had their planes of reflection 

 at right anglm to one another, he observed that the light transmitted 

 through the system exhibited phenomena similar to those whirh ure 

 seen along the axis of quartz. He succeeded in exhibiting before the 



Academy, in 1822, a division of the pencils, so that a line appeared 

 double, by making the light pass through prisms of glass which were 

 subject to strong pressure by mesa* of screws ; and he was the first 

 who observed the change produced by heat on the tints of sulphate of 

 time, a subject which has since been more completely investigated by 

 M. Mitecherlich. 



Apparently unacquainted with what had been previously proposed 

 by lirewster for a like purpose, this philosopher and engineer devised 

 several constructions of great lenses for lighthouses ; one of these 

 constructions consisted of five concentric spherical zones (plano- 

 convex) of glass disposed about a central lens, the whole being con- 

 tained in a square frame. Eight of these, in vertical positions, 

 constituted an octagonal case or lantern, which revolved about a 

 vertical axis, and had in its centre a powerful lamp. Another con- 

 struction consisted of two great lanterns, as they may bo called, one 

 within the other; the convex surface of each was formed of thin 

 cylindrical refractors, and both revolved about a lamp in their common 

 axis : the cylinders were so disposed as to produce, by the revolution, 

 incessant Hashes of light. 



Fresnel made some experiments for the purpose of decomposing 

 water by means of a magnet; and the method which he pursued con- 

 sisted in producing a currant in an electro-magnetic helix inclosing a 

 bar-magnet covered with silk ; on plunging the ends of the wire in 

 water, he obtained some remarkable effects; but, being unable to 

 account for certain anomalies which he observed, ho abandoned tho 

 project 



(Uuleau, Notict tur Prttnd ; Biographic Univertdle.) 

 FRESNOY, 1)U. [UUKRESNOT.] 



FKEY, JACOB, one of the most able, engravers of the 18th century, 

 was born at Lucern in 1631. After learning the first rudiments of 

 engraving of a cousin in his native place, he went to Rome, where he 

 obtained employment from and was instructed by Westerhout, who 

 also introduced him to the notice of Carlo Maratta, with whom he 

 perfected himself as a draughtsman. Frey made an engraving for 

 Maratta of a drawing of 'Hercules and the Serpent,' after Aunibal 

 Caracci, which excited that painter's admiration and astonishment. 

 Frey had used the needle more than was customary at that time with 

 engravers a practice which Maratta recommended him strongly to 

 pursue. 



Frey soon obtained the reputation of the greatest engraver at Rome 

 and of his time. He engraved in all eighty pieces, including many of 

 the finest work* of Italian art. Among the principal are ' St Jerome,' 

 and ' Martyrdom of St Sebastian,' after Domenichino ; ' St. Romualdo,'' 

 after Sacchi ; a copy of a ' Holy Family,' by Kdelinck, after UaiLtelle ; 

 the 'Aurora,' after Ouido ; and several admirable plates after Maratta, 

 Cignani, Annibal Caracci, and others. The 'Aurora,' after Ouido, was 

 one of Frey'e favourite pieces ; it is beautifully drawn, and the 'Hours' 

 have a surprising degree of buoyancy and motion : though less careful 

 in the detail of the accessaries, Prey's is a very superior print to that 

 made by Raflaello Morghen of the same subject, especially in tho 

 extremities and general treatment of the ' Hours ' and ' Aurora,' which 

 are the essential portion of tho composition. Ho died at Rome in 

 1 7.VJ. There in a notice of him and a li.,t of his works in J. C. Fuessli's 

 ' Qesohichte der besteu Kunstlcr in der Schweitz ;' there is also an 

 account of him in Qandellini's ' Xotizie Istoriche degli Intagliatori ' 



FRISUHLIN, N1CODEMUS, born in 1547, was the son of a 

 Protestant clergyman in the duchy of Wurteinberg. He showed at 

 an early age a great aptitude for the study of languages, became an 

 accomplished scholar, and was made professor in the University of 

 Tubingen, where he wrote his Paraphrases of Virgil's Bucolics and 

 Georgia*, and of Persius, as well as a great quantity of original poetry, 

 and so feral dramas, for one of which, entitled 'Uebecca,' he was 

 crowned with a gold laurel crown by the Emperor Kudolf II. at tha 

 Diet of Uatisbon, with the title of poet-laureate. But his satiric*! 

 humour mode him enemies, and, being charged with adultery, he was 

 obliged to leave Tubingen. After visiting several towns of Germany, 

 he at hist settled at Mayence, where he published some of his works. 

 In consequence, it would seem, of fresh satirical effusions from hi* 

 pen, the Duko of Wurtemberg caused him to be arrested at Mayeuce, 

 and shut up in a tower, whence he attempted to escape, but foil in so 

 doing from a great height, and died of the fall in November 1.190, 

 being forty-three year* of age. He wrote a groat number of works) 

 tl.o principal of which are : 1, ' De Astronomic^ Arti* cum D. 

 Ccolesti et Naturali PhUoaophia conveuieutiii;' 2, ' Institutione* 

 Omtoiuo;' 3, several Orations; 4, a work on education entitled 'De 

 liatione iustituendi Puerum ab anno tetaus sexto vel septimo ad 

 annum usque sextumdeciuium ;' 5, ' Uialogu* Logicus contra P. Kami 

 Sophisticain pro Aristotle,' and other treatues against the schoolmen ; 

 6, ' Fucotio) Selcctiores,' many of them licentious ; 7, ' Qusestionuui 

 Orammaticarum, libri octo ;' 8, ' In Tryphiodori .Kgyptii Urammatici 

 libru m do Ilii excidio, interprctatio duplex et nutas ad textum Onooum ;' 

 9, ' Motes on Callimachus ;' 10, 'Aristophanes repurgatus a mendis et 

 intorpretatus;' 11, 'In ebrietatern Caruiina ;' and a quantity of verses, 

 elegies, satire*, epigrams, besides tho dramas and tho paraphrases of 

 classic authors above mentioned. 



FKIS1, PAOLlJ, a distinguished Italian mathematician, was born 

 at Milau, April 13, 172$, of a family which came originally from 

 Strasbourg; and at fifteen yean of age he was placed in a monastery 



