Fish, shark, and snakes are all examples of animals that locomote using undulatory locomotion.
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In addition to a rostral to caudal kinematic wave that travels down the animals body during undulatory locomotion, there is also a corresponding wave of muscle activation that travels in the rostro-caudal direction. However, while this pattern is characteristic of undulatory locomotion, it too can vary with environment.
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Swimming hydrodynamics have significantly applied BCF (body- caudal fin swimming) to techniques. In addition research on undulatory motion, undulatory Body-caudal fin anguilliform, and undulatory Median-paired fin give interesting conclusions. These natural modes are seen as an alternative to BCF techniques introducing some missing elements as buoyancy, gliding and floating to complement the scale of man’s hydrodynamics.31\. Lindsey, C. C. (1978) Form, function and locomotory habits in fish, in Fish Physiology VII Locomotion, W. S. Hoar and D. J. Randall, Eds.
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Snakes primarily rely on undulatory locomotion to move through a wide range of environments Undulatory locomotion is the type of motion characterized by wave-like movement patterns that act to propel an animal forward. Examples of this type of gait include crawling in snakes, or swimming in the lamprey. Although this is typically the type of gait utilized by limbless animals, some creatures with limbs, such as the salamander, forgo use of their legs in certain environments and exhibit undulatory locomotion. In robotics this movement strategy is studied in order to create novel robotic devices capable of traversing a variety of environments.
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The stingray uses its paired pectoral fins for moving around. This is in contrast to sharks and most other fish, which get most of their swimming power from a single caudal (tail) fin. Stingray pectoral fin locomotion can be divided into two categories: undulatory and oscillatory. Stingrays who use undulatory locomotion have shorter thicker fins for slower motile movements in benthic areas.
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Sardines use Body-Caudal fin propulsion to swim and hold their pectoral, dorsal, and anal fins flat against the body, creating a more streamlined body and reducing drag. Most fish swim by generating undulatory waves that propagate down the body through the caudal fin. This form of undulatory locomotion is termed Body-Caudal Fin (BCF) swimming on the basis of the body structures used.Blake, R.W. (2004) Review Paper: Fish functional design and swimming performance.
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Kutchicetus' limbs and sacrum were probably weight-bearing and it probably swam using undulatory movements like modern otters and most likely Ambulocetus. This mode of locomotion represents a transitional stage in whale evolution.
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Sardines use body- caudal fin propulsion to swim, holding their pectoral, dorsal, and anal fins flat against the body, creating a more streamlined body to reduce drag. Most fish swim by generating undulatory waves that propagate down the body through the caudal fin. This form of undulatory locomotion is termed body-caudal fin (BCF) swimming on the basis of the body structures used; it includes anguilliform, sub-carangiform, carangiform, and thunniform locomotory modes, as well as the oscillatory ostraciiform mode.
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Derived tupilakosaurs possess embolomerous centra in their vertebrae, which are diplospondylous. They also have a deep notch in the pterygoid bone of the palate. Tupilakosaurs were aquatic, and used an undulatory mode of swimming much like that of eels.
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Most fully aquatic vertebrates do not use paddling modes of locomotion, instead using undulatory modes of locomotion or flipper locomotion. Fully aquatic mammals and animals typically have flippers instead of webbed feet, which are a more heavily specialized and modified limb. It is hypothesized that an evolutionary transition between semiaquatic and fully aquatic higher vertebrates (especially mammals) involved both the specialization of swimming limbs and the transition to underwater, undulatory modes of motion. However, for semiaquatic animals that mainly swim at the surface, webbed feet are highly functional; they trade-off effectively between efficient terrestrial and aquatic locomotion.
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C. trematoides grows to 2.5 cm in length. It swims at approximately 12 cm/s, by passing several undulatory waves down its body each second.Sea Slugs of Hawaii It is flattened and transparent; its internal organs are visible.Marine species identification portal: Cephalopyge and Cephalopyge trematoides.
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The skin of these animal that use undulatory motion to locomote have several distinct characteristics. The skin of these animals consists of cross-helical arrangement of collagen and elastin fibers embedded in the dermal layer of skin,D.M. Pearson.Functional aspects of the skin in polypterus fishes. Zool.
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27 Based on an average of 52 samples, the Orienta Sandstone is composed of: 33.3% nonundulatory quartz, 29.7% undulatory quartz, 17.3% potassium feldspar and 9.4% silicic volcanic clasts. Smaller constituents are 3.9% polycrystalline quartz, 2.3% opaques, 1.6% mafic volcanic clasts, 0.9% metamorphic, 0.7% sedimentary, and 0.4% plagioclase.
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In undulatory swimming modes, thrust is produced by wave-like movements of the propulsive structure (usually a fin or the whole body). Oscillatory modes, on the other hand, are characterized by thrust produced by swiveling of the propulsive structure on an attachment point without any wave-like motion.
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The early mosasauroid Vallecillosaurus also preserves body scales, but they are larger and more varied in shape, suggesting that the animal relied on undulatory movement in its trunk rather than just its tail. Plotosaurus, a more derived mosasaur than Platecarpus, has even smaller scales covering its body, indicating that it had even more efficient locomotion in the water.
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In undulatory swimming modes thrust is produced by wave-like movements of the propulsive structure (usually a fin or the whole body). Oscillatory modes, on the other hand, are characterized by thrust production from swiveling of the propulsive structure on an attachment point without any wave-like motion.Sfakiotakis, Michael, David M. Lane, and J. Bruce C. Davies. (1999) Review of Fish Swimming Modes for Aquatic Locomotion.
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Like vainikas, he used to sing to the tune of his violin play. Govindaswami Pillai's violin play is also marked by his brilliant alapanas and kalpana swaras and he had mastered the technique of tana playing by the undulatory movement of the bow. His period coincided with the later part of the life of the legendary Tirokodikaval Krishna Ayyar. Papa Venkataramayya was among his important disciples.
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The disc served as a combined diaphragm and armature. On speaking into the mouthpiece, the iron diaphragm vibrated with the voice in the magnetic field of the bar-magnet pole, and thereby caused undulatory currents in the coil. These currents, after traveling through the wire to the distant receiver, were received in an identical apparatus. This design was patented by Bell on January 30, 1877.
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The loss of forelimbs and reduction of hind limbs in Eupodophis was likely an adaptation for swimming. While living snakes usually employ undulatory movement for moving over land, sinuous movements are also an effective means of moving through water. Large, well-developed limbs increase drag on swimming animals, so the limbs of Eupodophis and other early snakes may have become vestigial to save energy and make movement more efficient.
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The sandstone is well-cemented and contains no glacial deposits and no fossils. The grains of Jacobsville Sandstone range from in size. Based on an average from samples taken in Marquette and Alger counties, Jacobsville Sandstone is composed of: 27.4% nonundulatory quartz, 27.0% undulatory quartz, 23.0% potassium feldspar, and 12.3% silicic volcanic clasts. Smaller constituents are 3.8% polycrystalline quartz, 2.4% metamorphic, 1.4% sedimentary, 1.3% opaque, 0.8% mafic volcanic, and 0.1% plagioclase.
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Flickiidae has been divided into two subfamilies, the Flickiinae, which is equivalent to the Flickiidae of the Treatise on Invertebrate Paleontology, Part L, 1957 and the Salaziceratinae which contains Salaziceras, moved from the Lyelliceratidae and Neosaynoceras, moved from the Acanthoceratidae. Genera now in the Flickiinae: :Flickia Pervenquiere, 1907 \- Shell smooth, moderately evolute, rather compressed, venter narrowly arched, suture smooth, undulatory. U Alb -L Cenom. N Afr, Madag, Texas.
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The posterior margin of the whorl is closely appressed against the preceding volution but not conspicuously elevated. The suture line is feeble, and undulatory. The aperture is narrow, widening a little behind by reason of the feeble expansion of the outer lip and the slightly less feeble constriction on the inner. The siphonal notch is broad, shallow, and placed perceptibly nearer to the periphery than to the posterior suture.
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Furthermore, these sorts of systems follow the capacitor or spring analogy, in the sense that the dominant degree of freedom in the energy is the generalized position. In more physical language, these systems are predominantly characterised by their potential energy. This often works for solids, or (linearized) undulatory systems near equilibrium. On the other hand, flow systems may be easier described by the hydraulic analogy or the diffusion equation.
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Eel and fish locomotion Engineers often focus on functional design. For example, designers attempt to create robots with flexible bodies (like real fish) that can exhibit undulatory motion. This kind of body enables the robot fish to swim similar to the way live fish swim, which can adapt and process a complicated environment. The first robot fish (MIT's RoboTuna) was designed to mimic the structure and dynamic properties of a Tuna.
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Video of singing bird The crested lark is a songbird, and has a liquid, warbling song described onomatopoeically as a ' or a '. It sings in flight from high in the sky, at roughly above the ground. The related Eurasian skylark exhibits similar behaviour but also sings during its ascent, whereas the crested lark sings either at altitude or on the ground. Their flight pattern is an example of undulatory locomotion.
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Soft bodied animals such as starfish rely on the arrangement of the fibers in their tube feet for movement. Eels, snakes, and fish use their skin like an external tendon to generate the propulsive forces need for undulatory locomotion. Vertebrates that fly, glide, and parachute also have a characteristic fiber arrangements of their flight membranes that allows for the skin to maintain its structural integrity during the stress and strain experienced during flight.
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Uppermost 20 m contains a variety of limestones. Lower contact with the Wills Creek is probably conformable. Upper contact is conformable and undulatory, occurring at the base of the "calico" limestone of the Keyser Formation.Faill, R.T., Glover, A.D., and Way, J.H., 1989, Geology and mineral resources of the Blandburg, Tipton, Altoona, and Bellwood quadrangles, Blair, Cambria, Clearfield and Centre Counties, Pennsylvania: Pennsylvania Geological Survey Topographic and Geologic Atlas, 4th series, 86, 209 p.
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A standing wave is an undulatory motion that stays in one place. A sinusoidal standing wave includes stationary points of no motion, called nodes, and the wavelength is twice the distance between nodes. The upper figure shows three standing waves in a box. The walls of the box are considered to require the wave to have nodes at the walls of the box (an example of boundary conditions) determining which wavelengths are allowed.
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More recently, studies on hydrodynamic detection in the California sea lion (Zalophus californianus) have been done. Despite the structure of their mystacial vibrissae, different from those of seals, these sea lions can detect and follow a trail made by a small toy submarine. Sea lions use an undulatory pattern of tracking similar to that in seals, but do not perform as well with increased delay before they are allowed to swim and locate the trail.
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The building has eight levels that provide spaces for over 1200 staff and students. Three of these floors are distinguished for its state of art teaching, learning and research facilities, which have been located underground. The organic form of the building is inspiredby the shapes of grove of trees. The undulatory form of the building is inflected by 700 multicoloured coloured, box-like openings piercing the glossy off-white surface of the façade.
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Other evidence for near shore, semi-aquatic lifestyle is where the fossils are found, often in transitional marine sediments.Andrade RCLPd, Saya ̃o JM (2014) Paleohistology and Lifestyle Inferences of a Dyrosaurid (Archosauria: Crocodylomorpha) from Paraíba Basin (Northeastern Brazil). PLoS ONE 9(7): e102189. doi:10.1371/journal.pone.0102189 -using axial frequency swimming (that used primarily by extant crocodylians) with a greater undulatory motion and frequency of the tail due to highly developed musculature allowing a more powerful forward thrust.
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Fins also increase the tail's surface area, increasing speed. The streamlined body of the fish decreases the amount of friction from the water. A typical characteristic of many animals that utilize undulatory locomotion is that they have segmented muscles, or blocks of myomeres, running from their head to tails which are separated by connective tissue called myosepta. In addition, some segmented muscle groups, such the lateral hypaxial musculature in the salamander are oriented at an angle to the longitudinal direction.
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Rajiformes is one of the four orders in the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as rajiform locomotion. The eyes and spiracles are located on the upper surface of the head and the gill slits are on the underside of the body.
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In 1841 he published his Examples of the Processes of the Differential and Integral Calculus, which expanded the earlier work of John Herschel, George Peacock and Charles Babbage to include the mathematics used to describe discontinuities observed in heat transfer explored by the French mathematician Joseph Fourier, and the theory of undulatory light, a topic familiar to him.Mathematical Writings of Ellis, pp. 198–9. He was elected a member of the Philological Society 12 May 1843.Proceedings – Philological Society (Great Britain), Volume 1, No. 9, (London, 1844).
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The same is true of amphibians – caecilians, Sirenidae (a clade of salamanders that are limbless except for atrophied front limbs), Amphiumidae (a clade of salamander with extremely atrophied limbs that appear non-functional) and at least three extinct groups (Aïstopoda, Lysorophia, and Adelospondyli). Larval amphibians, tadpoles, are also often limbless. Legless forms of reptiles and amphibians probably evolved so as to be able to move underground or in water more easily. Some analyses suggest that elongation and undulatory locomotion (slithering) evolved first, before limb loss.
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A seal is capable of following this center of this trail, either following the direct path of the trail or using an undulatory pattern involving crossing the trail repeatedly. This latter pattern might allow the seal to track a fish swimming in a zigzagging motion, or assist with tracking weak trails by comparing the surrounding water with the prospective trail.Gläser, N, S Wieskotten, C Otter, G Dehnhardt, and W Hanke. “Hydrodynamic trail following in a California sea lion (Zalophus californianus).” Journal of Comparative Physiology A 197, no.
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Under Forbes he was awarded prizes for essays on methods of physical inquiry and on the undulatory (or wave) theory of light. During vacations, he assisted his father who, from 1830, was manager and, later, effective treasurer and engineer of the Edinburgh and Dalkeith Railway which brought coal into the growing city. He left the University of Edinburgh in 1838 without a degree (which was not then unusual) and, perhaps because of straitened family finances, became an apprentice to Sir John Benjamin Macneill, who was at the time surveyor to the Irish Railway Commission.
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Fish live in fresh or saltwater habitats and some exceptions are capable of coming on land (mudskippers). Most fish have a line of muscle blocks, called myomeres, along each side of the body. To swim, they alternately contract one side and relax the other side in a progression which goes from the head to the tail. In this way, an undulatory locomotion results, first bending the body one way in a wave which travels down the body, and then back the other way, with the contracting and relaxing muscles switching roles.
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Davidson features uneven topography, in large part due to the area’s origins as a mining quarry, as well as its proximity to Garigal National Park. Steep descents are evident in Stone Parade, Borgnis Street and Maitland Street, whereas more undulatory landscapes can be seen along parts of Prahran Avenue and Kambora Avenue. The Eucalyptus trees and Liquid Ambers that line the streets of Davidson provide a pleasant backdrop for those living in the suburb. They also provide a haven for large numbers of native birds such as Kookaburras, Galahs and Rainbow Lorikeets.
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Meucci's telephone There has been much dispute over who deserves recognition as the first inventor of the telephone, although Bell was credited with being the first to transmit articulate speech by undulatory currents of electricity. The Federazione Italiana di Elettrotecnica has devoted a museum to Meucci making a chronology of his inventing the telephone and tracing the history of the two trials opposing Meucci and Bell.L'invenzione del telefono da parte di Meucci e la sua sventurata e ingiusta conclusione, aei.it. . Museo Storico Virtuale dell'AEIT Sala Antonio Meucci, aei.it. .
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Wilber suspended Bell's application for 90 days to give Gray time to submit a competing patent application. The suspension also gave Bell time to amend his claims to avoid an interference with an earlier patent application of Gray's that mentioned changing the intensity of the electric current without breaking the circuit, which seemed to the examiner to be an "undulatory current" that Bell was claiming. Such an interference would delay Bell's application until Bell submitted proof, under the first to invent rules, that Bell had invented that feature before Gray.
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Snakes can exhibit 5 different modes of terrestrial locomotion: (1) lateral undulation, (2) sidewinding, (3) concertina, (4) rectilinear, and (5) slide-pushing. Lateral undulation closely resembles the simple undulatory motion observed in many other animals such as in lizards, eels and fish, in which waves of lateral bending propagate down the snake's body. The American eel typically moves in an aquatic environment, though it can also move on land for short periods of time. It is able to successfully move about in both environments by producing traveling waves of lateral undulations.
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Their locomotion was relative to the water mass in which they lived but the exact mechanisms (such as turbulence, buoyancy, active swimming, and so forth) are not clear yet. The most likely option was rowing or swimming by undulatory motion with muscular appendages or with the feeding tentacles. However, in some species, the thecal aperture was probably so restricted that the appendages hypothesis is not feasible. On the other hand, buoyancy is not supported by any extra thecal tissue or gas build- up control mechanism, and active swimming requires a lot of energetic waste, which would rather be used for the tubarium construction.
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These currents, after traversing the wire, passed through the receiver which consisted of an electromagnet in a tubular metal can having one end partially closed by a thin circular disc of soft iron. When the undulatory current passed through the coil of this electromagnet, the disc vibrated, thereby creating sound waves in the air. This primitive telephone was rapidly improved. The double electromagnet was replaced by a single permanently magnetized bar magnet having a small coil or bobbin of fine wire surrounding one pole, in front of which a thin disc of iron was fixed in a circular mouthpiece.
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This lizard also has bead-like eyes so it can close them to keep sand out of its eyes. Similarly, its nostrils are very small to keep all of the sand out of its nose and lungs. X-ray imaging has demonstrated the lizard swims within sand using an undulatory gait with its limbs tucked against its sides rather than use its limbs as paddles to propel itself forward. Subsequent studies of the mathematics of sandfish sand-swimming, using robotic models, and electromyography show that the sandfish uses the optimum waveform to move through the sand with minimal energetic cost, given its anatomy.
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Orthogneiss thumb Undulose extinction or undulatory extinction is a geological term referring to the type of extinction that occurs in certain minerals when examined in thin section under cross polarized light. As the microscope stage is rotated, individual mineral grains appear black when the polarization due to the mineral prevents any light from passing through. If a mineral is deformed plastically by dislocation processes without recovery, strain builds up within the crystal lattice causing it to warp. This means that different parts of a crystal reach extinction at slightly different angles, giving the crystal an irregular, mottled look.
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Similarly to the aerodynamics of flight, powered swimming requires animals to overcome drag by producing thrust. Unlike flying, however, swimming animals often do not need to supply much vertical force because the effect of buoyancy can counter the downward pull of gravity, allowing these animals to float without much effort. While there is great diversity in fish locomotion, swimming behavior can be classified into two distinct "modes" based on the body structures involved in thrust production, Median-Paired Fin (MPF) and Body-Caudal Fin (BCF). Within each of these classifications, there are numerous specifications along a spectrum of behaviours from purely undulatory to entirely oscillatory.
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Similarly to the aerodynamics of flight, powered swimming requires animals to overcome drag by producing thrust. Unlike flying, however, swimming animals do not necessarily need to actively exert high vertical forces because the effect of buoyancy can counter the downward pull of gravity, allowing these animals to float without much effort. While there is great diversity in fish locomotion, swimming behavior can be classified into two distinct "modes" based on the body structures involved in thrust production, Median-Paired Fin (MPF) and Body-Caudal Fin (BCF). Within each of these classifications, there are numerous specifications along a spectrum of behaviors from purely undulatory to entirely oscillatory based.
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The aperture is narrow with a smooth callus. The whorls of the protoconch are probably 3 in the adult; those of the spire 10. The protoconch is smooth, highly polished, and somewhat papillate, the initial whorl for the most part submerged, the succeeding volution rather low and broadly inflated, the final whorl of the protoconch flattened laterally and relatively high. The line of demarcation between the spire and the protoconch is initiated by a protractive thickening of the shell and the introduction of 10 to 12 undulatory protractive riblets on the earlier whorls of the spire, persistent from the appressed posterior margin to the anterior suture.
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The beginning of the conch is marked by the initiation of 5 spiral lirae, the posterior of which is the broadest, and the anterior, which outlines the periphery, the most elevated. The sculpture is modified on the later volutions by the increasing prominence of the peripheral spiral and that directly behind it, the intercalation of secondaries, and the development of undulatory axials 8 to 10 to the whorl. These are indicated chiefly in the crenulation of the peripheral spirals. The periphery of antepenult whorls is situated a little more than one third of the distance across from the anterior to the posterior suture, outlined by a simple elevated spiral cord.
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In 1876, Alexander Graham Bell was granted a patent for the electromagnetic transmission of vocal sound by undulatory electric current. Despite the longstanding general crediting of Bell with the accomplishment, the Italian Ministry of Cultural Heritage and Activities supported celebrations of Meucci's 200th birthday in 2008 using the title "Inventore del telefono" (Inventor of the telephone).Manifestazioni per il bicentenario della nascita di Antonio Meucci, archive date 22 July 2011. The U.S. House of Representatives also honored Meucci in a resolution in 2002 for having had some role in the development of the telephone, although the U.S. Senate did not join the resolution and the interpretation of the resolution is disputed.
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In 1921 he was recruited by Robert Millikan to come to the California Institute of Technology, where he remained for the rest of his career. In 1922 he published 3 papers on Bohr's quantum mechanics in the Zeitschrift für Physik and one in the Physical Review. In 1926 he published the paper "The Stark Effect from the Point of View of Schrodinger's Quantum Theory" in the Physical Review, as well as "The New Quantum Theory and the Zeeman Effect" (1926), and "The Magnetic Dipole in Undulatory Mechanics" (1927). In 1920 Epstein calculated the effect of Polflucht as a possible causing force of Wegener's continental drift.
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Several factors support that P. capensis represents the tracks of O. augusti; the average external width of P. capensis is comparable to that of fossils of O. augusti, the distal spines of the swimming leg of O. augusti could have caused such bilobed marks and Onychopterella represents the only Ordovician eurypterid from those deposits. In addition, the median line could have been produced by the telson touching the substrate. O. augusti would have been able to make incursions to the terrestrial surface, but it would have been uncomfortable for it, performing an undulatory gait and keeping its telson in regular contact with the ground, hence the median line. But nevertheless, this can not be completely proven unless a specimen of O. augusti is found alongside similar tracks.
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"This hypothesis of Mr.Fresnel is at least very ingenious, and may lead us to some satisfactory computations: but it is attended by one circumstance which is perfectly appalling in its consequences. The substances on which Mr.Savart made his experiments were solids only; and it is only to solids that such a lateral resistance has ever been attributed: so that if we adopted the distinctions laid down by the reviver of the undulatory system himself, in his Lectures, it might be inferred that the luminiferous ether, pervading all space, and penetrating almost all substances, is not only highly elastic, but absolutely solid!!!" — Thomas Young (written January 1823), Sect. in "Refraction, double, and polarisation of light", Supplement to the Fourth, Fifth, and Sixth Editions of the Encyclopædia Britannica, vol.
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The Philips Pavilion at the time of the exhibition. Design by Xenakis Although he was an illegal immigrant in Paris, Xenakis was able to get a job at Le Corbusier's architectural studio. He worked as engineering assistant at first, but quickly rose to performing more important tasks, and eventually to collaborating with Le Corbusier on major projects. These included a kindergarten on the roof of an apartment block in Nantes (Rezé) (Also: Unité d'Habitation of Nantes-Rezé), parts of government buildings in Chandigarh, India, the "undulatory glass surfaces" of Sainte Marie de La Tourette, a Dominican priory in a valley near Lyon, and the Philips Pavilion at Expo 58—the latter project was completed by Xenakis alone, from a basic sketch by Le Corbusier.
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In 1828, he was elected a foreign member of the Royal Swedish Academy of Sciences. In optics, Arago not only made important optical discoveries on his own, but is credited with stimulating the genius of Jean-Augustin Fresnel, with whose history, as well as that of Étienne-Louis Malus and Thomas Young, this part of his life is closely interwoven. Shortly after the beginning of the 19th century the labours of at least three philosophers were shaping the doctrine of the undulatory, or wave, theory of light. Fresnel's arguments in favour of that theory found little favour with Laplace, Poisson and Biot, the champions of the emission theory; but they were ardently espoused by Humboldt and by Arago, who had been appointed by the Academy to report on the paper.
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The net cost of transport (NCT), which indicates the amount of energy required to move a unit of mass a given distance, for a snake moving with a lateral undulatory gait is identical to that of a limbed lizard with the same mass. However, a snake utilizing concertina locomotion produces a much higher net cost of transport, while sidewinding actually produces a lower net cost of transport. Therefore, the different modes of locomotion are of primary importance when determining energetic cost. The reason that lateral undulation has the same energetic efficiency as limbed animals and not less, as hypothesized earlier, might be due to the additional biomechanical cost associated with this type of movement due to the force needed to bend the body laterally, push its sides against a vertical surface, and overcome sliding friction.
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Among Arago's many contributions to the support of the undulatory hypothesis, comes the experimentum crucis which he proposed to carry out for measuring directly the velocity of light in air and in water and glass. On the emission theory the velocity should be accelerated by an increase of density in the medium; on the wave theory, it should be retarded. In 1838 he communicated to the Academy the details of his apparatus, which utilized the relaying mirrors employed by Charles Wheatstone in 1835 for measuring the velocity of the electric discharge; but owing to the great care required in the carrying out of the project, and to the interruption to his labours caused by the revolution of 1848, it was the spring of 1850 before he was ready to put his idea to the test; and then his eyesight suddenly gave way. Before his death, however, the retardation of light in denser media was demonstrated by the experiments of H. L. Fizeau and B. L. Foucault, which, with improvements in detail, were based on the plan proposed by him.
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