have been worked for over a hundred years; in North Carolina, California, and Oregon, and several places in Canada. It is also found in the form of sand in some places in North America, India, and New Zealand. One of the largest occurrences of magnetic sand is on the south shore of Long Island, near Quogue, where a furnace was built and an attempt made to work it; but the enterprise proved unsuccessful and was abandoned. Liquid Air.- Popular attention has been | Pennsylvania, the most noted locality being attracted to this subject recently in America by Cornwall, Lebanon County, where the mines the experiments of Mr. Charles E. Tripler, although the liquefaction of gases is by no means new. It was first accomplished by Northmore in 1806, who succeeded in obtaining liquid chlorine by pressure. Faraday followed. Two factors are necessary to liquefy a gas, pressure and cold. Every gas, so far as now known, will liquefy under a given pressure, provided it is cooled to a certain temperature known as its critical temperature." In 1877 two French experimenters, Pictet, Cailletet, working separately, and along different lines, succeeded in liquefying oxygen. This was followed in 1883 by successful experiments by two Russian physicists, Wrobleski and Olszewski. Among other surprising results they succeeded in freezing alcohol. It was not until 1890 that liquid air and oxygen were produced in any quantity. This was first done by Prof. Dewar, of the Royal Institution, London. About this time Mr. Tripler, of New York, developed a form of apparatus which may be said to be a practical machine. The capacity of his plant is about 40 gallons per day. The process claimed by this physicist is also claimed by Mr. Thompson in England, and Dr. Carl Linde of Munich, Germany. The effects of the intense cold which can be produced by evaporating liquid air, oxygen, or hydrogen are almost beyond comprehension; practically all plastic or soft materials when immersed in it become hard and brittle, leather being an exception; some metals become brittle, and can be broken or crumbled; alcohol may be frozen, and air and oxygen themselves solidify if placed in liquid hydrogen. The possibilities of liquid air are many. It can be used for refrigeration; motor vehicles and launches can be operated by it; surgeons can use it in operations, and for ventilating and cooling rooms it is invaluable. The com Mariner's Compass.- The Chinese ascribed the invention of the compass to their Emperor Hong-Ti, who they say was a grandson of Noah; some of their historians refer the invention of it to a later date, 1115 B. C. The honor of its discovery, however, though much disputed, is generally given to Flavio Gioja, a native of Amalfi, an ancient commercial city of Naples, A. D. 1302. pass is also said to have been known to the Swedes in the time of King Jarl Birger, 1250. The variation of the needle was first discovered by Columbus in his voyage of discovery, 1492. The compass box and hanging compass, used by navigators, were invented by William Barlowe, an English divine and natural philosopher, in 1608. The measuring compass was invented by Jost Bing, of Hesse, in 1602. The dipping needle was invented by Robert Norman, a compass maker of Ratcliffe, England, in 1580. Matches, Invention of.- Previous to 1829 the matches in use consisted of a slender stick with a pointed end, which had been dipped in sulphur; and they were lighted by touching them to a spark struck into tinder by flint and steel. In that year, however, what was known as the "Instantaneous Light-Box" was invented. It consisted of a small tin box containing a bottle, in which was placed some sulphuric acid, with sufficient fibrous asbestos Magnet. -The iron ore which possesses to soak it up and prevent its spilling out of the the property of attraction was given the name bottle, and a supply of properly prepared of magnet by the Greeks, because it was first matches. These consisted of small splints of found in Magnesia in Asia Minor, or accord- wood about two inches long, one end of ing to another account because it was first dis- which was coated with a chemical mixture covered by a shepherd named Magnes, who prepared by mixing chlorate of potash, powhad iron tips on his shoes, and while walking dered loaf-sugar and powdered gum arabic, over some rocks found that his feet stuck to the whole colored with a little vermilion, and them in a mysterious way. The ore is now made into a thin paste with water. The splints called magnetite, and is an oxide of iron con- were readily inflamed by dipping the prepared These were suctaining about seventy-three per cent. of iron ends into the sulphuric acid. when pure. It is a very valuable ore, and ceeded by the lucifer, or loco-foco match, supplies a large amount of the finest iron and which was ignited by friction; and that, in steel of commerce. Large deposits occur in turn by the Congreve, which was similar to Norway and Sweden, Finland and the Ural; the sulphur matches now in use; and this, in the Adirondack region in northern New shortly afterward, by the present parlor match. York; in northern New Jersey; in eastern Maxim Self-Acting Gun was invented by Hiram S. Maxim of England. The peculiar features of this gun are: Every round after the first is fired by the recoil of the previous explosion; the cartridges are picked out of the cartridge belt, one end of which is placed in the gun mechanism on one side by the automatic action of the gun, and the belt and cartridge shells are ejected after firing; every recoil of the gun brings the next cartridge into position, forces it into the barrel, cocks the hammer, pulls the trigger, extracts the empty shell, and ejects it from the gun-all these processes going on with such marvelous rapidity that six hundred rounds are fired in a minute. The gun can be turned in any direction by means of a crank, and the rate of discharge is regulated by a controlling chamber, ingeniously contrived so that the gun may be fired rapidly or slowly, as desired. At the moment of firing, the recoil drives the barrel back about three quarters of an inch, and it is this recoil which directs the mechanism of the gun and makes its discharges continuous. It which is the meaning of its German name. Mesmerism was first brought into notice by Frederick Anton Mesmer, a German physician, in 1766, when he published a thesis on "The Influence of the Planets on the Human Body," claiming that the heavenly bodies diffused through the universe a subtle fluid which acts on the nervous system of animated beings; and he further stated that he regarded the new force, which, he said, could be exerted by one living organism upon another, as a means of alleviating or curing disease. In 1778 he left Vienna for Paris, where he gained numerous proselytes and much money. His discovery was fostered by Dr. D'Elson, physioian to the king's brother, and in 1784 the French government ordered the medical faculty of Paris to investigate Mesmer's theory. A committee was appointed, who subsequently reported that "The violent effects which are Medicine appears to have been first practiced by the Egyptian priests. Pythagoras endeavored to explain the philosophy of disease and the action of medicine about 529 B. C. Hippocrates, the Father of Medicine, flour-observed in the public practice of magnetism ished about 422 B. C., and Galen, born A. D. are due to the manipulations, to the excite131, was the oracle of medical science. About ment of the imagination which leads us to 980, Avicenna, an Arab, wrote a system of repeat anything which produces an impression medicine. The art was brought into Europe upon the senses." One year later, 1785, from the East, about A. D. 1150. In the Mesmer's popularity had so far declined that early stages of the practice, the preparation of he left Paris and retired to Switzerland, where simples was principally confined to ecclesiastics he spent the balance of his life. Mesmerin Europe generally, until the close of the fif-ism excited some attention again in 1848, teenth century. The dogmatic age of medi- when Miss Harriet Martineau and others ancine lasted until the Reformation, when it was nounced their belief in it. attacked by Paracelsus (1493-1541) and Vasalius (1514-64). Since 1800 medical practice has been completely transformed by physiological and chemical research. The practice of medicine is now one of the highest sciences, and in most countries is in the hands of learned and distinguished men; various statutes have been enacted to discourage pretenders to the healing art. Meteors. Meteors are small, erratic bodies rushing through the planetary system, and, getting hot in the process, appear in the atmosphere surrounding our earth as "shooting stars." Some of these falling bodies have reached the earth, and such are called “aërolites" or "meteorites." Numbers, of course, are burned up before they reach us, and who can tell what destruction such a catastrophe may represent, or whether it be or be not an inhabited world which has thus been plunged to destruction by fire? They are of a metallic or stony nature. On certain nights in August and November it has been calculated that these meteors will appear. They fall from certain constellations, after which they are named; as Leonides, from Leo, in the November displays. Meerschaum is a mineral existing in many parts of the world. In Europe, it is found chiefly at Hrubschitz in Moravia, and at Sebastopol and Kaffa in the Crimea; and in Asia it is found abundantly just below the soil in the alluvial beds at Kittisch and Bursa in Natolia; and in the rocks of Eske-Hissar, in the same district, it is mined so extensively as to give employment to nearly a thousand men. Meerschaum, from its having been found on The star showers sometimes present the apthe seashore in some places, in peculiarly pearance of a beautiful display of rockets. rounded snow white lumps, was ignorantly Millions of them rush round the sun, and imagined to be petrified froth of the sea, when, as occasionally happens, our earth comes near them, we have a grand display of assembled at Paris to settle, from the results celestial fireworks. of the great Meridian Survey, the exact length of the definitive meter.' As a result of the investigations of this learned body, the Metric System was based upon the length of the fourth part of a terrestrial meridian. The ten-millionth part of this arc was chosen as the unit It is estimated that the average number of meteors that traverse the atmosphere daily, and which are large enough to be visible to the eye on a dark, clear night, is 7,500,000; and if to these the telescopic meteors be added, the number will be increased to 400,000,000. | of measures of length, and called Meter. The In the space traversed by the earth there are, on the average, in each volume the size of our globe (including its atmosphere), as many as 13,000 small bodies, each one capable of furnishing a shooting star visible under favorable circumstances to the naked eye. cube of the tenth part of the meter was adopted as the unit of capacity, and denominated Liter. The weight of a liter of distilled water at its greatest density was called Kilogramme, of which the thousandth part, or Gramme, was adopted as the unit of weight. The multiples Metric System, The, originated in France of these, proceeding in decimal progression, are about 1790. In 1799, on the invitation of distinguished by the employment of the prethe Government, an international convention, fixes deca, hecto, kilo, and myria (ten, hundred, at which were present representatives from thousand, ten thousand) from the Greek, and France, Holland, Denmark, Sweden, Switzer- the subdivisions by deci, centi, and milli (tenth, land, Spain, Savoy, and the Roman Republics, hundredth, thousandth) from the Latin. Microphone, The, is the black carbon button used in telephones, and is an instrument for magnifying sound. The most sensitive substance, so far as yet discovered, to have the peculiar power, when placed in the electric current, of magnifying sound, is willow charcoal plunged, when at white heat, into mercury. A piece of such charcoal an inch long, placed vertically between two blocks of carbon, hollowed to receive its ends, wires connecting the blocks with an electric battery, and the ordinary receiving instrument of a telephone, con 0.0395383 3.9528290 395.3828959 Sq. Roods. Sq. Acres. 0.0009885 0.0002471 0.0988457 0.0247111 9.8845724 2.4711434 stitute one of the simplest forms of a microphone. The invention of the microphone is claimed by Professor Hughes of England, and Thomas Edison, the American inventor. Microscope, Invention of the.- It is generally believed that the first compound microscope was made in 1590 by a Hollander named Zacharias Jansen. Pocket microscopes were first made in London in 1740 by Benjamin Martin. The discovery of the magnifying power of the simple lens was undoubtedly made long before the Christian era, as it is с known that the Greeks used magnifiers of glass which they called "reading-glasses," and rude lenses of crystal have been found in Egyptian ruins. also much used for the ornamentation of churches, in which it formed a large portion of the wall decoration. Christian mosaics admit, says one writer, of two general diviMirage. Mirage (sometimes called Fata sions, the later Roman and the Byzantine Morgana) is the appearance in the air of the styles, the material in use being in general image of some distant object, seen either in cubes of colored glass, inlaid, in the Roman connection with the object itself, above or be- school, on a ground of blue and white, although low the latter, or suspended in the air, the ob- in the latter the tesseræ are frequently irregular ject being invisible. It is a very curious but in size and the workmanship coarse. The sufficiently common phenomena, and in the former style flourished in Italy chiefly in the Asiatic and African plains it is frequently fifth and sixth centuries, the most splendid observed. When the weather is calm and the specimens being found in the churches of Rome ground hot, the Egyptian landscape appears and Ravenna. The Florentine mosaic dates like a lake, and the houses look like islands in from the time of the Medici, and is made enthe midst of a widely-spreading expanse of tirely of precious or semi-precious stones, such water. This causes the mirage, which is the as amethyst, agate, jasper, onyx, and others, result of evaporation, while the different tem-cut and inlaid in forms or thin veneers best peratures of the air strata cause an unequal reflection and refraction of light, which give rise to the mirage. Travelers are frequently deceived, but the camels will not quicken their usual pace until they scent water. The suited to produce the effects desired. objects represented are most frequently birds, flowers, fruits, vases, sometimes buildings, and more rarely portraits and landscapes. In reference to the present Roman mosaics, it may be said that the smalti or small cubes of colored glass which compose the pictures are stuck into the cementing paste, or mastic, in the same manner as were the colored glass, stone, and marble sectilia and tessera of the ancients. Within quite recent years mosaics of surpassing beauty, both in design and material, have been produced by Russian artists in the Imperial Glass Manufactory of Russia. The Fata Morgana and the inverted images of ships seen at sea are not uncommon on European coasts. Between Sicily and Italy this phenomenon is seen in the Sea of Reggio with fine effect. Palaces, towers, fertile plains, with cattle grazing on them, are seen, with many other terrestial objects, upon the sea-the palaces of the Fairy Morgana. The inverted images of ships are frequently perceived, and many most extraordinary but perfectly authentic tales have been related concerning the re-to the whistling of the winds in hollow reeds. flection and refraction of persons and objects in the sky and on land, when no human beings nor any of the actual objects were within the range of vision. Mirrors. In ancient times mirrors were made of metal; those of the Jewish women of brass; mirrors of silver were introduced by Praxiteles, 328 B. C. Mirrors or lookingglasses were made at Venice, A. D. 1300; and in England, at Lambeth, near London, in 1673. The French excelled in their manufacture of them in the last century. Various methods of coating glass by a solution of silver, thus avoiding the use of mercury, so injurious to the health of the workman, have been made known, by M. Petitjean, in 1851; by M. Cimeg, in 1861, and by Liebig and others. Music. Lucretius ascribes its invention Franckinus, to the various sounds produced by the hammers of Tubal-Cain; Pontique and others to the singing of birds; and Zarlino to the sound of water. It is however agreed that music was first reduced to rules by Jubal, 1800 B. C. The flute and harmony or concord in music was invented by Hyagnis, 1506. Vocal choruses of men are first mentioned 56 B. C. The first six musical notes are said to have been invented by Guy Aretino, a Benedictine monk of Arezzo, about 1025. The notes of present use were perfected in 1338. Musical pitch was settled in France in 1859. Pythagoras maintained that the motion of the twelve spheres must produce delightful sounds inaudible to mortal ears, which he called the music of the spheres. Saint Cecilia, a Roman lady, Mosaics.—The origin of the art of produc- is said to have excelled so eminently in music, ing artistic designs by setting small square that an angel was enticed from the celestial repieces of stone or glass of different colors, so gions by the fascinating charms of her melody; as to give the effect of painting, is obscure, this hyperbolical tradition has been deemed but it was much practiced by the Romans, sufficient authority to make her the patroness especially for ornamental pavements, specimens of music. She died in the third century. of which are almost always found wherever Nails. It is only since 1810 that machinthe remains of an old Roman villa are discovery has been employed to any extent in the ered. Under the Byzantine empire it was manufacture of nails. Previous to that date, nearer they are to the central orb. Certain points are assumed in this hypothesis to explain the distribution of matter in our solar system. It is assumed that in throwing off great masses from the central disc, immense quantities of minute particles were also thrown, which continue to revolve, in the same plane with the large mass around the central body. By slow degrees these minute atoms, by the law of gravitation, were aggregated into the mass nearest to them. These subordinate aggregations would form with most difficulty nearest the large central mass, because of the superior attractive force of the latter, wherefore the interior planets- Mercury, Venus, the Earth, and Mars are smaller than the two great orbs in the zone beyond them. These two enormous planets, Jupiter and Saturn, occupy the space where conditions are most favorable to subordinate aggregations; but beyond them the gravity of aggregating material becomes reduced, and so the planets found in the outer zone, Uranus and Neptune, are smaller than the planets of the middle zone. This hypothesis was first suggested by Sir William Herschel, and was adopted and developed by Laplace. they were made by hand by forging on anvolving around it in orbits; the smaller, the anvil, and great numbers of men were employed in the industry, there having been as many as 60,000 nailers in the neighborhood of Birmingham alone. It appears that as early as 1606 a patent was obtained for cutting nail rods by water power, by Sir Davis Bulmer. An improvement on this was patented in 1618, and a new invention in 1790, which last was the first nail machine in actual use; it was patented by Thomas Clifford, and used in French's factory at Wimburn, Staffordshire, in 1792. Toward the close of the last century many patents were obtained in the United States for new machines and improvements on old ones. Many of the first inventors spent large sums of money on their machines, and it has been estimated that it cost fully $1,000,000 to bring them to the perfection attained in 1810, when a machine made 100 nails a minute. The machine invented by Jesse Reed of Massachusetts, about 1800, is the one which first came into general use, and this, with some improvements, is the one most largely used to-day. In 1810, Joseph C. Dyer of Boston, then a merchant in London, took out patents in England for the nail machinery invented in Massachusetts. It was at once widely introduced, and large manufacturing establishments were soon founded. Some factories at Birmingham are now capable of making over 40,000,000 nails a week. The term penny, used to indicate the size of nails, is supposed to be a corruption of pound; thus a fourpenny nail was one such that 1,000 of them weighed four pounds; a tenpenny, such that 1,000 weighed ten pounds. Originally, the “hundred,” when applied to nails, meant sixscore, or 120; consequently the thousand was 1,200. In France, the greater part of the nails used in carpentry-work are made of soft iron wire, pointed with the hammer, and the head is formed by pinching them in a toothed vise. Nebular Hypothesis.-The Nebular Hypothesis assumes that the solar system was once an enormous mass of gaseous substance. Rapid rotation arising in this gaseous mass, it took the form of a disc, and at last inertia (popularly but erroneously called centrifugal force), overcoming cohesion, whole rings and fragments flew off from this disc, and by gravitation contracted into spheroid masses. As, in the original mass, the velocity of the outer circle of each body thrown off is greater than the inner circle, this causes each spheroid to revolve on its own axis. This process goes on, and the central mass continues to cool and shrink until we have at last a central body with a number of smaller spheroidal bodies re Needles. The making of Spanish needles was first taught in England by Elias Crowse, a German, about the eighth year of Queen Elizabeth, and in Queen Mary's time there was a negro who made fine Spanish needles in Cheapside, London. At his death the secret of fabrication was lost, and not recovered again till 1566. The family of Greenings, ancestors of Lord Dorchester, established a needle factory in Bucks a little later. German and Hungarian steel is of best repute for needles. The manufacture was greatly improved at White Chapel, London; Redditch, in Gloucestershire; and Hathersage, in Derbyshire. An exhibition of ancient needles and needlework was formed at South Kensington museum in 1873. Nickel was first obtained as a metal in Germany about 1751; but the ore had been previously known to miners, who called it kupfernickel, or Old Nick's copper, for the reason that, though it looked like copper ore, no copper could be obtained from it. Nickel, when pure, is silvery white, and does not oxidize or tarnish in the air. It is found in many parts of the world, but the principal mines are in Russia, Sweden, Germany, Austria, England, and Scotland, and in the states of Pennsylvania and Connecticut in America. Its chief use is for plating other metals, but it is also used in alloys. Oceans, Depths of. The average depth of all the oceans is from 2,000 to 3,000 |