possession of goods in three instances: 1. When the common law compels the members of any particular trade or business, without any option on their part, to accept employment from every person who is willing to pay a reasonable compensation, in recompense for the burden which it thus throws upon them, it allows them to detain such goods as are delivered to them in the course of their business, until the owner has satisfied any debt which may have arisen out of the transaction in which the goods were so delivered. Innkeepers, common carriers and farriers are entitled to this species of lien; for instance, the proprietor of a coach need not give up a parcel until the carriage of it be paid for. 2. When goods are delivered to a tradesman, or any other, to expend his labor upon, he is entitled to detain those goods until he is remunerated for the labor which he so expends. Thus a tailor is not obliged to take a customer's cloth and make it into a coat, but, if he consents to make the coat, the customer cannot compel him to deliver it until he is paid for the making. The first kind seems to be included in the second, but they are kept distinct, because it is supposed that the first was, at one time, the only species of lien allowed by the common law, and that the second was a subsequent invention, adopted on equitable considerations in limitation of it. 3. When goods have been saved from the perils of the sea, the salvor may detain them until his claim for salvage is satisfied; but the finder of goods has in no other case a lien on the goods found, in respect of the trouble and expense to which the finding and preserving of them may have subjected him. All these are particular liens; and, therefore, the coach proprietor may not detain the parcel, nor may the tailor detain the coat, nor the salvor the property saved, until payment of the carriage of a former parcel, or of the price of another coat, or of salvage which accrued for saving other goods. Another rule with regard to particular liens is, that they exist only so long as the possession of the goods is retained by the person who has the lien. If he once deliver up the goods to the owner, he waves his lien, which is thereby so effectually annihilated, that it will not be revived, even if the same goods should afterwards return into his possession. Thus, if the tailor deliver the coat, and it is afterwards sent to him to be mended, he cannot then detain it as a security for the original price, but only for the cost of mending. His remedy to re46

VOL. VII.

cover the price must be by a suit at law; and we may here remark, that a creditor can never prejudice his right of maintaining an action for his demand, by insisting on his right of detaining the goods, for the action and the lien are concurrent rights, and do not interfere with each other. -II. General liens are only created by express agreement, or by usage. It has been determined, that attorneys and solicitors, bankers, factors and brokers, insurance-brokers, and some others, are, by the custom of their respective trades and professions, entitled to a lien on the property of their clients, customers and employers, for the general balance of their accounts. Thus an attorney may detain papers which have been delivered to him to assist in the conducting of one cause, as a security for the costs of another; and, if he return them to his client, and they come again into his possession, his lien revives; for, in the case of a general lien, it matters not whether the same or different papers are delivered to the person employed, his right of detaining being the same in both instances.

LIEOU-KIEOU. (See Loo-Choo.)

LIEUTENANT. This word, like captain (q. v.), and many others, has received gradually a much narrower meaning than it had originally. Its true meaning is a deputy, a substitute, from the French lieu (place, post) and tenant (holder). A lieutenant général du royaume is a person invested with almost all the powers of the sovereign. Such was the count d'Artois (afterwards Charles X) before Louis XVIII entered France, in 1814. The duke of Orleans, before he accepted the crown as LouisPhilip, was appointed to the same office by the chamber of deputies. Lieutenantgeneral was formerly the title of a commanding general, but at present it signifies the degree above major-general. Lieutenant-colonel is the officer between the colonel and major. Lieutenant, in military language, signifies the officer next below a captain. There are first lieutenants, and second, or sous-lieutenants, with different pay. A lieutenant in the navy is the second officer next in command to the captain of a ship. According to the new organization of the French navy, of 1831, there are lieutenants de vaisseau and lieutenants de frégate, formerly called enseignes de vaisseau. The latter can command only in the absence of the former. In England, the lord-lieutenant of a county has the authority to call out the militia in case of invasion or rebellion. The governor of Ireland is also called lord-lieuten

ant of Ireland. In some English colonies, jointly under a governor-general, the chief magistrate of each separate colony is called lieutenant-governor. Many of the U. States choose lieutenant-governors to act in case of the governor's death, &c.

LIFE. (See Physiology.)

LIFE-PRESERVERS. The human body is a little lighter than an equal bulk of water, so that it naturally floats in this fluid. The mouth, however, in the case of most men lying motionless in the water, would sink below the surface, if the head were not thrown back by a muscular effort. Many persons who fall into still water, and are unable to swim, might be saved, if they had presence of mind sufficient to preserve a proper position. The specific levity of the body, in comparison with water, makes it easy to keep the upper part of it considerably elevated above the surface of the water by attaching to the chest some buoyant substance, even though its bulk be not great; and many contrivances, called life-preservers, have been invented with this view. A great portion of them, however, have been found, in practice, of little or no use. One of the latest is the invention of a Mr. Scheffer, in England. It consists of a hollow cylinder, formed without a seam, and perfectly air-tight, bent when distended with air and ready for use or it is what may be termed a cylindrical ring, without a seam, and without a break. Of this ring, the external diameter is generally about 22 inches, the internal diameter about 12, and the diameter of the cylinder about 54, the dimensions varying, of course, by being specially adapted to the size of the person by whom it is designed to be employed. It contains a small stop-cock, to which an ivory pipe is fixed. Through this pipe the air is injected by the mouth, and retained by the stop-cock; the adjustment and inflation only occupying the short space of one minute. When unexpanded, it folds up into a very small compass, so as to be conveyed in the pocket; and is also very portable, its weight being but twelve ounces. Another life-preserver, invented in the U. States, by a gentleman of Connecticut, does not differ essentially from this, except that it is a straight cylinder. It is made of cloth without a seam, and rendered impervious to water by a preparation of caoutchouc, is about two feet, or two and a half feet long, and eight or ten inches in diameter; is filled like the one first described, and secured to the body by means of straps passing over the shoulders. When empty,

it occupies but little room, and may even be worn by a man laboring on the deck of a vessel in danger. He can inflate it in a few moments, when he finds it necessary to trust himself to the waves.

LIGAMENT, in anatomy; a strong, compact substance, serving to join two bones together. A ligament is more flexible than a cartilage, not easily ruptured or torn, and does not yield, or at least yields very little, when pulled.

LIGATURE, in surgery, is a cord, band, or string; or the binding any part of the body with a cord, band, fillet, &c., whether of leather, linen, or any other matter. Ligatures are used to extend or replace bones that are broken or dislocated; to tie the patients down in lithotomy and amputations; to tie upon the veins in phlebotomy, on the arteries in amputations, or in large, wounds; to secure the splints that are applied to fractures; to tie up the processes of the peritoneum, with the spermatic vessels, in castration; and, lastly, in taking off warts or other excrescences by ligature. Ligature is also used to signify a kind of bandage or fillet, tied round the neck, arm, leg, or other part of the bodies of men or beasts, to divert or drive off some disease, accident, &c.

LIGATURES, among printers, are types consisting of two letters or characters joined together; as ff, fi, fl. The old editions of Greek authors are extremely full of ligatures; the ligatures of Stephens are by much the most beautiful.

LIGHT is that which renders objects perceptible to our sense of seeing. It is one of the most interesting subjects that fall under the contemplation of the philosopher at the same time it must be acknowledged to be one that is as little understood, and upon which opinions are as much divided, as any of the most abstruse subjects of philosophical inquiry. Some consider light as a fluid per se; while others consider it merely as a principle, and attribute to it a sort of pression, or vibration propagated from the luminous body through a subtile, ethereal medium. The ancients believed it to be propagated from the sun and other luminous bodies instantaneously; but the observations of the moderns have shown that this was an erroneous hypothesis, and that light, like any other projectile, employs a certain time in passing from one part of space to another, though the velocity of its motion is truly astonishing, as has been manifested in various ways. And first, from the eclipses of Jupiter's satellites; it was ob served by Roemer, that the eclipses of

those satellites happen sometimes sooner and sometimes later than the times given by the tables of them, and that the observation was before or after the computed times, according as the earth was nearer to or farther from Jupiter than the mean distance. Hence it was concluded that this circumstance depended on the distance of Jupiter from the earth; and that, to account for it, we must suppose that the Light is 14 minutes in crossing the earth's orbit. The original observations have received some corrections, and it is now found that, when the earth is exactly between Jupiter and the sun, his satellites are seen eclipsed about eight minutes and a quarter sooner than they could be according to the tables; but when the earth is nearly in the opposite point of its orbit, these eclipses happen about eight minutes and a quarter later than the tables predict them. Hence, then, it is certain that the motion of light is not instantaneous, but that it takes up about 16 minutes of time to pass over a space equal to the diameter of the earth's orbit, which is nearly 190,000,000 of miles in length, or at the rate of 200,000 miles per second-a conclusion which, it may be added, is placed beyond doubt, by the aberration of the stars discovered by the celebrated doctor Bradley. Upon the subject of the materiality of light, doctor Franklin observes, in expressing his dissent from the doctrine that light consists of particles of matter continually driven off from the sun's surface, with such enormous swiftness "Must not the smallest portion conceivaable have, with such a motion, a force exceeding that of a 24 pounder discharged from a cannon? Must not the sun diminish exceedingly by such a waste of matter, and the planets, instead of drawing nearer to him, as some have feared, recede to greater distances, through the lessened attraction? Yet these particles, with this amazing motion, will not drive before them or remove the least and slightest dust they meet with, and the sun appears to continue of his ancient dimensions, and his attendants move in their ancient orbits." He therefore conjectures that all the phenomena of light may be more properly solved, by supposing all space filled with a subtile elastic fluid, not visible when at rest, but which, by its vibrations, affects that fine sense in the eye, as those of the air affect the grosser organs of the ear; and even that different degrees of vibration of this medium may cause the appearances of different colors. And the celebrated Euler has maintained

the same hypothesis, urging some further objections to the materiality of light, besides those of doctor Franklin above alluded to. Newton first discovered that certain bodies exercise on light a peculiar attractive force. When a ray passes obliquely from air into any transparent liquid or solid surface, it undergoes, at its entrance, an angular flexure, which is called refraction. The variation of this departure from the rectilineal path for any particular substance, depends on the obliquity of the ray to the refracting surface; so that the sine of the angle of refraction is to that of the angle of incidence in a constant ratio. Newton, having found that unctuous or inflammable bodies occasioned a greater deviation in the luminous rays than their attractive mass, or density, gave reason to expect, conjectured, that both the diamond and water contained combustible mattera conjecture which was verified by subsequent discovery. Doctor Wollaston invented a very ingenious apparatus, in which, by means of a rectangular prism of flint glass, the index of refraction of each substance is read off at once by a vernier, the three sides of a movable triangle performing the operations of reduction in a very compendious manner. (Phil.Trans., 1802.) But transparent media occasion not merely a certain flexure of the white sunbeam, called the mean refraction: they likewise decompose it into its constituent colors. This effect is called dispersion. Now, the mean refractive and dispersive powers of bodies are not proportional to each other. In some refracting media, the mean angle of refraction is smaller, whilst the angle of dispersion is larger. From the refractive power of bodies, we may, in many cases, infer their chemical constitution. For discovering the purity of essential oils, an examination with doctor Wollaston's instrument is of great utility, on account of the smallness of the quantity requisite for trial. This idea of doctor Wollaston has been happily prosecuted by M. Biot with regard to gaseous compounds; and we now have accurate tables of the refractive power of all transparent gaseous, liquid and solid bodies. Carburet of sulphur exceeds all fluid substances in refractive power, surpass ing even flint glass, topaz and tourmalin ; and in dispersive power, it exceeds every fluid substance except oil of cassia. Rays of light, in traversing the greater number of crystallized bodies, are commonly split into two pencils; one of which, called the ordinary ray, follows the common laws of refraction, agreeably to the tables alluded

to, whilst the other, called the extraordinary ray, obeys very different laws. This phenomenon is produced in all transparent crystals, whose primitive form is neither a cube nor a regular octahedron. The division of the beam is greater or less, according to the nature of the crystal, and the direction in which it is cut; but, of all known substances, that which produces this phenomenon in the most striking manner, is the crystallized carbonate of lime, called Iceland spar. If the white sunbeam, admitted through a small hole of a window-shutter into a darkened room, be made to pass through a triangular prism of glass, it will be divided into a number of splendid colors, which may be thrown upon a sheet of paper. Newton ascertained that if this colored image, or spectrum, as it is called, be divided into 360 parts, the red will occupy 45, the orange 27, the yellow 48, the green 60, the blue 60, the indigo 40, and the violet 80. The red rays, being least bent by the prism from the directionof the white beam,are said to be least refracted, or the least refrangible, while the violet rays, being always at the other extremity of the spectrum, are called the most refrangible. If these differently colored rays of light be now concentrated on one spot, by a lens, they will reproduce colorless light. Newton ascribes the different colors of bodies to their power of absorbing all the primitive colors, except the peculiar one which they reflect, and of which color they therefore appear to our eye. The different colored rays possess very different powers of illumination. The lightest green, or deepest yellow, which are near the centre, throw more light on a printed page than any of rays towards either side of the spectrum. The rays of the prismatic spectrum differ from one another also in their heating power, as was first noticed by Herschel. In viewing the sun, by means of large telescopes, through differently colored darkening glasses, he sometimes experienced a strong heat, attended with very little light, and, at other times, he had a strong light with a little heat. This observation led to his well known researches upon this subject, from which he concluded that the maximum heat is just without the spectrum, beyond the red ray. Others have found the greatest heat in the red ray itself; but the recent observations of M. Seebeck have shown that the point of greatest heat was variable, according to the kind of prism which was employed for refracting the rays. When a prism of fine flint glass is used, the greatest heat is constantly

the

beyond the red; when a prism of crown glass, the greatest heat is in the red itself. It has long been known, that the solar light is capable of producing powerful chemical changes. One of the most striking instances of it is its power of darkening the white chloride of silver-an effect which takes place slowly in the diffused light of day,but in the course of two or three minutes by exposure to the sunbeam. This effect was formerly attributed to the influence of the luminous rays; but it appears, from the observations of Ritter and Wollaston, that it is owing to the presence of certain rays, that excite neither heat nor light, and which, from their peculiar agency, are termed chemical rays. It is found that the greatest chemical action is excited just beyond the violet ray of the prismatic spectrum, and that the spot next in energy is occupied by the violet ray itself, and that the property gradually diminishes as we advance to the green, beyond which it seems wholly wanting. The sunbeams, in traversing a colored glass, produce similar effects to those caused by the differently colored portions of the spectrum. Thus the chloride of silver acquires a black tint behind a blue or violet glass, but does not blacken behind a red or orange glass; on the other hand, it becomes red behind a red glass, and that much more quickly than even in the solar spectrum. Light produced by coal and oil gases, or by olefiant gas, even when concentrated so as to produce a sensible degree of heat, was found, by Mr. Brande, to occasion no change in the color of muriate of silver, nor in mixtures of chlorine and hydrogen; while the light emitted by electrized charcoal speedily affected the muriate, and caused these gases to unite, and sometimes with explosión. The concentrated light of the moon, like that of the gases, produced no change. The importance of light to plants is well known: deprived of it, they become white, and contain an excess of saccharine and aqueous parti cles; and flowers owe the variety and in tensity of their hues to the influence of the solar beams. Even animals require the presence of the rays of the sun, and their colors seem materially to depend upon the chemical influence of these rays. A comparison between the polar and tropical animals, and between the parts of their bodies exposed, and those not exposed to light, shows the correctness of this opinion. (For an account of the physical affections, and other chemical effects of light, see Optics, Phosphorescence, and Polarization of Light.)